Marine Mammals and

Persistent Ocean Contaminants:

Proceedings of the Marine Mammal Commission Workshop

Keystone, Colorado, 12-15 October 1998

Edited by

Thomas J. O’Shea, Workshop Chairman

U.S. Geological Survey 

Midcontinent Ecological Science Center

4512 McMurry Avenue

Fort Collins, Colorado 80525-3400

Randall R. Reeves

Okapi Wildlife Associates

27 Chandler Lane

Hudson, Quebec J0P 1H0, Canada

Alison Kirk Long

Marine Mammal Commission

4340 East-West Highway, Room 905

Bethesda, Maryland 20814

April 1999

Marine Mammal Commission

4340 East-West Highway, Room 905

Bethesda, Maryland 20814
e
i

TABLE OF CONTENTS

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Section I: BACKGROUND AND OBJECTIVES ..............................1

Introduction ......................................................1

The Marine Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Workshop Objectives .....................................................3

Workshop Agenda and Procedures ..........................................4

Acknowledgments .......................................................5

Section II. PRINCIPAL WORKSHOP FINDINGS

AND CONCLUSIONS

......................................................................7

Major . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

 Uncertainties

......................................................................7

Principal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Section III. WORKING GROUP REPORTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Working Group on Immunotoxicology, Pathology, and Disease . . . . . . . . . . . . 21

Pathology and Disease Subgroup Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Immunotoxicology Subgroup Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

. Working Group on Endocrinology and Reproduction . . . . . . . . . . . . . . . . . . . . . 35

Working Group on Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Risk Characterization Subgroup Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Exposure Subgroup Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Measurement of Adverse Effects Subgroup Report . . . . . . . . . . . . . . . . . . . . . . 66

Surrogate Approaches Subgroup Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Case Study Subgroup Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

. Working Group on Future Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Section IV. EXTENDED ABSTRACTS

OF PLENARY PRESENTATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Persistent Ocean Contaminants and Marine Mammals: 

A Retrospective Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Reproductive and Developmental Effects of Endocrine-disrupting Chemicals on Marine
ii

Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Contaminants and Marine Mammal Immunotoxicology and Pathology . . . . . . . . . . . . 117

Assessing the Risks to Marine Mammal Populations 

from Exposure to Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Overview of Federal And International Programs 

on Contaminants in Marine Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Overview of Health, Ecological, and Economic Dimensions of Global Change:

Tracking Marine Disturbance and Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

A Framework for Analyzing the Origins of Contaminants 

in Marine Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

List of Tables:

List of Figures:

Figure 1. The framework for ecological risk assessment. 

Figure 2. The interplay of controlled laboratory or captive studies and field

correlative studies. 

Figure 3. Extrapolation in risk assessment: the “weight of evidence.” 

Figure 4. The integration of field and laboratory studies.

Figure 5. Major steroidogenic pathways in mammalian endocrine tissues. 

Figure 6. The U.S. National Research Council conceptual framework for the

process of risk assessment. 

Figure 7. An analysis of the distribution of contaminant burdens or

concentrations in “hosts.” 

Figure 8. A conceptual framework for analyzing the origin of contaminants

in marine mammals.

Figure 9. Tissues in the National Marine Mammal Tissue Bank. 
v

EXECUTIVE SUMMARY

The Marine Mammal Commission convened a workshop in Keystone, Colorado, 12–15 October

1998, to review what is known, and what needs to be learned, about the effects of persistent

ocean contaminants on marine mammals. Concern about the possible effects of anthropogenic

compounds and trace elements in marine mammals has increased in recent years for two main

reasons. The first is that disease outbreaks, involving marine mammals with high concentrations

of organochlorines in tissues, appear to have occurred with increasing frequency. The second is

that experimental and other evidence has shown that certain contaminants often found in the

tissues of marine mammals have deleterious effects on reproduction and the immune system.

Prompted by these and other contaminant-related concerns, the Marine Mammal Commission,

with the co-sponsorship of the U.S. Geological Survey, the National Marine Fisheries Service,

the Environmental Protection Agency, and the National Fish and Wildlife Foundation, organized

this international workshop, involving scientists from seven countries. Expertise of workshop

participants included environmental toxicology, environmental chemistry, marine mammal

health and husbandry, pathology and disease, physiology, immunotoxicology, marine mammal

population dynamics and ecology, experimental design, environmental risk assessment, and

wildlife epidemiology.

The workshop objectives were to (1) review and summarize the state of knowledge about the

types and levels of potentially harmful persistent contaminants found in marine mammals, and

about the known and potential effects of these substances on marine mammal health and

population dynamics; (2) identify and rank in importance the critical uncertainties concerning the

presence, levels, sources, fates, and effects of organochlorines, toxic elements, and other

persistent contaminants on marine mammals; (3) outline research and monitoring programs

needed to resolve the critical uncertainties as quickly as possible; and (4) assess how ongoing

and planned research and monitoring programs should be restructured or expanded. Much of the

focus of the workshop was on the persistent ocean contaminants classified as organochlorines. 

These include many compounds that originated as pesticides or industrial chemicals. Although

some countries no longer use or produce most of these compounds, they continue to be

manufactured and used in many parts of the world, and they are redistributed to the global

marine ecosystem by a variety of transport mechanisms. Marine mammals, many of which exist

at the top of complex ocean food webs, continue to be sinks for organochlorines. Only limited

consideration was given at the workshop to potentially toxic trace elements and other persistent

substances in the marine environment. This was primarily because there is much less evidence

suggesting direct harm to marine mammals from these substances. It was acknowledged that

marine mammals may also be regularly exposed to other contaminants, such as non-persistent

polyaromatic hydrocarbons from petroleum and industrial sources, but these contaminants were

not a focal subject of consideration.

The workshop consisted of a series of plenary addresses, each followed by a panel discussion,

and deliberations and report preparation by four working groups. These working groups were
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

vi

organized to address priority concerns in the following topic areas: immunotoxicology,

pathology, and disease; endocrinology and reproduction; risk assessment; and likely future

trends. The workshop report includes a summary of priority uncertainties and a list of 20

principal conclusions and recommendations derived from the working group reports (Section II),

detailed reports prepared by the working groups (Section III), extended abstracts of the plenary

presentations (Section IV), and a small series of appendices (Section V).

Reproductive problems observed during the 1960s and 1970s in female California sea lions off

southern California, female harbor seals in the Wadden Sea, and female ringed and gray seals in

the Baltic Sea were associated with high body burdens of organochlorines, particularly PCBs and

metabolites of DDT. A study of captive harbor seals in The Netherlands, published in 1986,

demonstrated an association between impaired reproduction and exposure to organochlorines in

the seals’ diet. Other studies in the 1980s and 1990s suggested that organochlorines affect

endocrine and immune function in some marine mammals. Beluga whales downstream from

heavily polluted portions of the St. Lawrence River–Great Lakes watershed and seals in the

Baltic Sea have various lesions strongly suggestive of contaminant effects. Die-offs of seals and

small cetaceans in Europe and North America from disease (primarily morbilliviruses) during

the late 1980s and 1990s evoked much public concern about the role of contaminants. Although

investigations of the links between disease outbreaks and contaminants based on studies of

carcasses were inconclusive, they led to experimental studies with harbor seals in Europe

showing organochlorine-linked effects on immunocompetence. Additional studies reviewed at

this workshop added weight to the argument that organochlorines have immunosuppressive

effects on marine mammals. 

The workshop concluded that there is good reason to be concerned that survival and

reproduction in certain marine mammal populations may have been affected, and are being

affected, by persistent contaminants, particularly organochlorines. The potential effects of

contaminants may include morbidity and mortality from acute toxicity (although mortality has

not yet specifically been shown in marine mammals), disruption of endocrine cycles and

developmental processes causing reproductive failures or birth defects, suppression of immune

system function, and metabolic disorders resulting in cancer or genetic abnormalities. Onset and

severity of potential effects may vary according to exposure level, the animal species, age, sex,

and general condition, and the presence of other contaminants (e.g., synergism, antagonism,

detoxification by enzyme induction, etc.). Concern was also expressed about the effects of

eutrophication of coastal waters by excessive inputs of nitrogen and phosphorus, which could

diminish the capacity of coastal fish and invertebrate communities to support marine mammal

populations, and which might lead to increased frequency and scale of toxic algal blooms that

are known to kill them. However, there remains great uncertainty about specific effects of

contaminants in marine mammals, to what extent such effects may occur in marine mammals in

the wild, and what impact such effects are having on marine mammal population dynamics. 

Seven general areas of uncertainty were defined by workshop participants as having the highest

priority for resolution. The closing of these knowledge gaps will make science better able to
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

vii

guide policy, management, and regulatory decisions related to contaminant impacts on marine

mammals. These are uncertainties about (1) the pathologic effects of persistent ocean

contaminants on marine mammals; (2) the relationships between exposure to environmental

contaminants and immunotoxicity or health effects specific to marine mammals; (3) the role of

environmental contaminants in marine mammal reproductive failure; (4) the potential impacts of

endocrine-disrupting contaminants on marine mammals; (5) predicting the risk to individual

marine mammals and to marine mammal populations associated with exposure to persistent

contaminants; (6) future trends with currently known contaminants; and (7) future trends with

less widely recognized contaminants.

For most of the past 40 years the study of marine mammals and contaminants has emphasized

determination of chemical residues in tissues. Contaminants have now been documented in many

thousands of individuals. However, much less emphasis has been placed on designing and

executing studies that allow interpretation of the significance of this contamination to marine

mammal health and population dynamics. A consistent theme during the workshop was the need

for multidisciplinary studies that integrate physiological, behavioral, reproductive, clinical,

pathologic, and toxicological data to evaluate the relationships of immune status, health,

reproduction, and survival of individuals to population- and ecosystem-level trends. Such

studies should be conducted on both wild and captive populations. Long-term research and

monitoring programs are especially valuable and need a stable funding base. Understanding the

subcellular mechanisms by which contaminants affect marine mammals can only be achieved

through in vitro studies using marine mammal cell lines or through experimentation. Invasive

experiments can use laboratory animals as surrogates for marine mammals, although variation in

response among species means that results must be treated with caution. Therefore,

establishment of dose-response relationships and response thresholds may require well-designed,

nonlethal experimentation with marine mammals. To a considerable extent, model species that

have been well studied and are readily available in captivity (e.g., California sea lions, harbor

seals, bottlenose dolphins, and beluga whales) can be used to represent other related species in

future field studies or research on captive marine mammals, although extrapolation must be done

judiciously. Because most marine mammals are exposed to multiple contaminants in nature,

experiments on cell lines, surrogate species, or captive marine mammals should include

exposures to complex mixtures in addition to single chemicals. Biochemical and physiological

indices of exposure or effects, often called “biomarkers,” can be useful monitoring tools. More

biomarkers need to be developed and validated for marine mammals. The workshop emphasized

the potential for major problems in the future with well-known contaminants, substances not yet

identified by current analyses, and many potential “new” contaminants that are being developed

or are already in production. Additional findings and more detailed recommendations are made

in each of the working group reports, extended abstracts, and appendices to this report. 
1

Section I. BACKGROUND AND OBJECTIVES

Introduction

All marine mammals alive today have been exposed

to chemical compounds and trace elements introduced to aquatic systems by human activities.

Many of these substances enter the aquatic environment directly as a result of runoff, leakage, dumping, or atmospheric transport. They are also dispersed and distributed in the environment via food

webs. As high-trophic level consumers, most

marine mammals experience the effects of biomagnification. They can acquire relatively large burdens of persistent pollutants by ingesting contaminated prey, and can also be exposed to airborne

contaminants while breathing. The physiological

processes involved in storage, metabolism, and

elimination of contaminants in marine mammals are

poorly understood, as are the effects of exposure.

Also, there is great uncertainty about the mechanisms and pathways of contaminant flux in marine

and freshwater environments.

The global marine ecosystem is the ultimate

repository for most well-known persistent contaminants, such as the organochlorines. It is well established that many of these contaminants have found

their way into the tissues of marine mammals during

the past 50 years, and with expanding world industrialization there is a likelihood that anthropogenic

chemical contamination of the oceans will increase

in amount and complexity. Concern about the

conservation and protection of marine mammals

inevitably extends to consideration of the role of

contaminants. How and to what extent does exposure to contaminants affect the health, reproduction,

and survival of individual marine mammals? What

are the implications of such effects for marine

mammal populations? Do contaminants play a role

in causing population declines or slowing population recoveries?

The possible negative impacts of contaminants

on marine mammal health and population trends

have received increasing attention over the past

three decades, and especially during the last few

years. Among the issues that have been raised are

(1) the apparently increasing incidence of disease

outbreaks, sometimes associated with seemingly

high levels of contaminant exposure; and (2) the

experimental and other evidence that certain contaminants often found in marine mammal tissues

have deleterious effects on survival and reproduction in other species. Marine mammal management

authorities have traditionally been preoccupied with

the problems of large-scale directed killing and

bycatch of marine mammals in fisheries. While

substantial progress has been made in addressing

these problems (at least in North America, Europe,

and Australasia), there has been a tremendous

growth in information documenting the presence of

contaminants in marine mammal tissues. This has

led to mounting concerns and uncertainties about

their effects in these species. Thus it is appropriate

for the impacts of environmental contaminants to

become an additional focus of scientific, management, and regulatory efforts directed toward marine

mammals.

Recognizing the issue’s importance, and the fact

that numerous organizations are giving increased

attention to contaminant-related research and monitoring, the Marine Mammal Commission, with the

cosponsorship of the U.S. Geological Survey, the

Environmental Protection Agency, the National

Marine Fisheries Service (National Oceanic and

Atmospheric Administration, Department of Commerce), and the National Fish and Wildlife Foundation, organized and convened the Workshop on

Marine Mammals and Persistent Ocean Contaminants. The workshop, held in Keystone, Colorado,

12–15 October 1998, was attended by 54 scientists

from seven countries (Appendix A). Their expertise

spanned a wide range of disciplines: environmental

toxicology, environmental chemistry, pathology and

disease, physiology, immunotoxicology, and marine

mammal health, husbandry, population dynamics

and ecology. Most participants had expertise on

contaminants in marine mammals; some were

experts in epidemiology, human and laboratoryanimal toxicology, and environmental risk assessment.

The workshop was organized by a steering
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

2

committee chaired by Thomas J. O’Shea of the U.S.

Geological Survey, Midcontinent Ecological Science Center, Fort Collins, Colorado. Other members of the committee were Gregory D. Bossart,

University of Miami; Michel Fournier, University

of Quebec at Montreal; Joseph R. Geraci, National

Aquarium in Baltimore; L. Earl Gray, Environmental Protection Agency, Research Triangle Park,

North Carolina; Robert J. Hofman, Marine Mammal

Commission; Robert Kavlock, Environmental

Protection Agency, Research Triangle Park; Alison

Kirk Long, Marine Mammal Commission; John S.

Reif, Colorado State University; and Teri K.

Rowles, National Marine Fisheries Service. 

Various aspects of the topic of marine mammals

and contaminants have also been considered by

other workshops and symposia held under different

auspices over the past decade. Chemical pollutants

and cetaceans were the focus of a workshop held in

Bergen, Norway in March 1995, convened by the

Scientific Committee of the International Whaling

Commission (Reijnders et al. 1999). In April 1995

a workshop in Lerwick, Shetland, U.K., was sponsored by the North Atlantic Marine Mammal Commission, and included a focus on the effects on

human health from eating contaminated marine

mammal products (Sanderson and Gabrielson

1996). A symposium devoted to the topic of marine

mammals and chemical contaminants was also

convened in Kamogawa, Japan, in February 1993

(Tatsukawa et al. 1994). Most recently, a workshop

was held in 1998 in Sidney, British Columbia, on

environmental contaminants and marine mammal

health, with an emphasis on the Pacific coast of

Canada and the United States (Ross and De Guise

1998). Broader information pertaining to Arctic

contamination that includes information on Arctic

marine mammals has been compiled by the Arctic

Monitoring and Assessment Program (AMAP) and

is available online at http://www.grida.no/amap. 

The Marine Mammals

There is no unambiguous definition of “marine

mammal.” However, the term has acquired a

customary meaning, at least within the United

States, as a result of the Marine Mammal Protection

Act of 1972. The Act defines marine mammals as

all members of the orders Cetacea (whales, dolphins, and porpoises) and Sirenia (manatees and the

dugong); all members of the three Carnivora families Phocidae (true or earless seals), Otariidae (fur

seals and sea lions), and Odobenidae (the walrus);

two members of the Carnivora family Mustelidae

(the sea otter and marine otter); and one member of

the Carnivora family Ursidae (the polar bear). From

a global perspective, this arbitrarily defined group

of animals lives in a large variety of habitats and

pursues diverse strategies for feeding, reproduction,

and other vital activities. Thus, they are exposed to

many kinds and levels of contaminants. Feeding

strategies, in particular, influence the nature and

degree of exposure to contaminants. Carnivorous

species that feed at relatively high trophic levels

tend to have higher body burdens of certain contaminants. Thus, for example, the planktivorous baleen

whales tend to have lower concentrations of organochlorines in their tissues than the more piscivorous

toothed whales (O’Shea and Brownell 1994). In

general, coastal populations of dolphins, seals, and

sea lions tend to have higher contaminant levels

than the more oceanic populations, presumably

because their food webs are more exposed to concentrated terrestrial run-off. Several species, such

as manatees, gray whales, and walruses, are benthic

feeders. By feeding in or near bottom sediments,

they risk exposure to types and concentrations of

contaminants that may differ from those to which

the more pelagic-feeding species are exposed. 

Although the title of this workshop refers to

persistent ocean contaminants, it is important to

bear in mind that some marine mammals (e.g., river

dolphins, manatees, freshwater seals) inhabit river

and lake systems deep within continental land

masses and far removed from marine environments.

The workshop’s emphasis on the marine environment was not meant to exclude consideration of the
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

3

freshwater species and populations of “marine”

mammals.

Workshop Objectives

The workshop had four primary objectives:

(1) To summarize what is known about the types

and levels of potentially harmful persistent

contaminants that have been found in marine

mammals throughout the world, and the known

and potential effects of these contaminants on

marine mammal health and population dynamics;

(2) To identify and rank by relative importance the

critical gaps in knowledge concerning the

presence, levels, sources, fates, and effects of

organochlorines, toxic elements, and other

persistent contaminants in marine mammals;

(3) To determine and describe the types of research

and monitoring programs, including new and

innovative approaches, that would be required

to resolve the most critical uncertainties as

quickly as possible; and

(4) To evaluate how certain ongoing and planned

research and monitoring programs could be

restructured or augmented to better meet critical

information needs.

Workshop Agenda and Procedures

The workshop agenda is given in Appendix B. The

first evening and most of the second day were

devoted to the first objective of summarizing the

knowledge about the types and levels of potentially

harmful persistent contaminants that have been

found in marine mammals throughout the world,

and their known and potential effects on marine

mammal health and population dynamics. This was

accomplished during seven plenary addresses, each

followed by a short question period and a half-hour

panel discussion. Extended abstracts of the seven

presentations are given in Section IV of this report,

and one of the full papers appears as Appendix C. 

This is the report by T. Rowles and L. Thorsteinson, which provides an overview of federal and

international programs on contaminants and marine

mammals. Two additional documents prepared at

the workshop are a part of this report. Appendix D

is a summary prepared by Anders Bergman that

provides an overview of historical and recent work

on contaminants in seals of the Baltic Sea, one of

the longest known cases of heavy contamination in

marine mammals. Appendix E is a statement

prepared during and after the workshop by Robert

Risebrough giving his perspective on the value of

controlled experiments in understanding the effects

of contaminants in marine mammals.

Participants were divided into four working

groups charged with meeting objectives 2–4. Following the verbal presentations at the workshop, a

brief plenary session was held to explain the terms

of reference and working procedures for these four

working groups. The subjects to be addressed by

the working groups were 

C Immunotoxicology, pathology, and disease;

C Endocrinology and reproduction; 

C Risk assessment; and

C Future trends.

The terms of reference and composition of the

working groups had been determined in advance by

the workshop steering committee, based on consultations by e-mail with all participants. Approximately two months before the workshop, participants were asked to list up to six of what they

considered the most pressing unanswered scientific

questions (critical uncertainties) regarding marine

mammals and contaminants. They were also asked

to indicate their preferences for working group

assignments and to provide lists of five or more

critical uncertainties and key issues specifically

related to each of the subjects to be addressed by the

working groups. The steering committee edited and

organized the participant-generated lists of critical

uncertainties and assigned them to the appropriate

working group. A briefing book sent to participants

prior to the workshop contained, for each working

group, a list of members, a list of the main topics to

be addressed (ranging in number from six to ten),
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

4

and a list of key issues and critical uncertainties

under each topic. Participants were urged to communicate with each other about these issues and

uncertainties prior to arriving at the workshop.

Working groups met briefly during the evening of Day 2 to begin their tasks of supplementing,

consolidating, and ranking issues and critical uncertainties. Explicit instructions were provided concerning written statements to be produced by the

groups. Each working group was asked to identify

the highest-priority issues and uncertainties in its

area of concern and to prepare written statements on

up to five of these. All of Day 3 was devoted to

working group meetings. A final plenary session

was held in the morning of Day 4. During this

session, working group leaders or rapporteurs

summarized their group’s findings and fielded

questions from all participants. After a brief discussion in plenary, the working groups reconvened to

review and revise their reports. Although the initial

expectation was that each group would break into

subgroups to develop and prepare statements on

particular subtopics and critical uncertainties, not all

groups functioned in this way.

The working group reports constitute the main

body of this report. They are presented in full in

Section III. The group and subgroup reports typically consist of sections that present the Issue Title,

Issue Description and Rationale, Means to Resolve

the Critical Uncertainties Surrounding the Issue, and

Suggestions Regarding Existing Monitoring and

Research Programs. This format reflects the guidelines provided by the steering committee to the

working groups, with the intention of establishing

consistency in the way issues and critical uncertainties were defined and addressed. However, during

deliberations some groups or subgroups modified

this reporting format to suit unique aspects of their

particular topic or approach. 

The working group reports were edited following the workshop by the leaders and rapporteurs,

then circulated to the respective group members for

review. The final submissions were subjected to

further editing by the report editors, and the draft

workshop report was then sent to all participants for

final review.

Acknowledgments

We thank the Marine Mammal Commission for

proposing the workshop, for organizing the early

planning phases, and for securing the generous

support of the U.S. Geological Survey, the National

Marine Fisheries Service, the Environmental Protection Agency, and the National Fish and Wildlife

Foundation. We thank the members of the Steering

Committee and the staff of the U.S. Marine Mammal Commission for their assistance in the detailed

planning of the workshop and all participants for

their dedication and efforts at Keystone. In particular, we thank the leaders and rapporteurs of working

groups and subgroups who persisted in seeing the

group findings and ideas through to the written

stage; they include Michael A. Castellini, Sylvain

De Guise, Douglas P. DeMaster, Joseph R. Geraci,

John Harwood, John Kucklick, Thomas P. Lipscomb, Mary B. Matta, Robert H. Mattlin, John E.

Reynolds, III, Teri K. Rowles, Lori Schwacke, and

Randall S. Wells. Whitney Tilt and staff at the

National Fish and Wildlife Foundation facilitated

many of the workshop logistics. John R. Twiss, Jr.,

of the U.S. Marine Mammal Commission provided

foresight, advice, and support for all phases of the

workshop. Robert J. Hofman of the Marine Mammal Commission provided many fine suggestions

that helped improve the workshop organization and

the final report. Teri Rowles of the National Marine

Fisheries Service was instrumental in workshop

planning and organization. For having contributed

substantial support for the workshop and follow-up

work, we thank Nancy Foster and Hilda DiazSoltero of the National Marine Fisheries Service and

William S. Fisher of the Environmental Protection

Agency. Pam Smith of the U.S. Geological Survey,

Midcontinent Ecological Science Center, assisted in

planning and in preparation of various workshop

documents. Suzanne Montgomery assisted in final

technical editing and preparation for publication. 

 T.J.O., R.R.R., A.K.L. 

References

O’Shea, T. J., and R. L. Brownell, Jr. 1994. Organo-
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5

chlorine and metal contaminants in baleen whales: a

review and evaluation of conservation implications.

The Science of the Total Environment 154:179–200.

Reijnders, P .J. H., G. P. Donovan, A. Aguilar, and A.

Bjørge (eds.). 1999. Report of the workshop on

chemical pollution and cetaceans. Journal of Cetacean Research and Management (Special Issue

1):1–42.

Ross, P. S., and S. De Guise (eds.). 1998. Environmental contaminants and marine mammal health: research

applications. Canadian Technical Report of Fisheries

and Aquatic Sciences 2255: v + 29 pp.

Sanderson, K., and G. W. Gabrielson (eds.). 1996.

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environment. A collection of papers presented at the

International Conference on Marine Mammals and the

Marine Environment, Lerwick, Shetland, U.K., 20–21

April 1995. The Science of the Total Environment

186:1–179.

Tatsukawa, R., S. Tanabe, N. Miyazaki, and T. Tobayama (eds.). 1994. Special issue: marine pollution —

mammals and toxic contaminants. A collection of

papers presented at the International Symposium on

Marine Pollution — Mammals and Toxic Contaminants, Kamogawa, Japan, 6–8 February 1993. The

Science of the Total Environment 154:107–256.
6

Section II. PRINCIPAL WORKSHOP FINDINGS

AND CONCLUSIONS

MAJOR UNCERTAINTIES

Prior to the workshop, participants generated a list

of more than 400 scientific issues and uncertainties

on the topic of environmental contaminants and

marine mammals. These were assembled in the

briefing book and used to guide decisions about

what to include in a list of the most important

knowledge gaps. The working group reports

(immunotoxicology, pathology and disease; endocrinology and reproduction; risk assessment; and

future trends) examine major gaps in knowledge as

defined by the expert participants, and discuss

measures that may be required to fill those gaps.

The high-priority uncertainties are summarized here

as well. 

Pathologic Effects of Persistent Ocean

Contaminants on Marine Mammals

Knowledge about contaminant-induced pathologic

effects and associated diseases in marine mammals

is limited even though very high levels of certain

contaminants have been documented repeatedly in

marine mammal tissues. More needs to be known

about the relationships among systemic and targetorgan exposure, tissue burden and distribution of

contaminants, body condition, and clinical and

pathologic effects. Failure to gain an understanding

of the pathologic effects of contaminants on marine

mammals will render scientists unable to inform and

advise policy makers, and marine mammal health

may deteriorate as ocean contamination continues.

Relationships between Exposure to

Environmental Contaminants and

Immunotoxicity or Other Health Effects

In recent years, there have been large-scale die-offs

of marine mammals caused by disease. Many of the

animals that died during these disease outbreaks had

high levels of organochlorine contaminants in their

tissues. Although many contaminants in the marine

environment, including organochlorines, heavy

metals, and polycyclic aromatic hydrocarbons

(PAHs), are well characterized as immunotoxicants

in laboratory animals, immunotoxic effects on

marine mammals have been demonstrated only to a

limited extent. If the effects of these contaminants

on marine mammals remain uncertain, it will be

difficult or impossible to assess the role of contaminants in future die-offs and in affecting population

trends. In addition, we will remain ignorant about

the possible chronic effects of contaminants on

marine mammal immune function. 

The Role of Environmental Contaminants

in Reproductive Failure

Field observations on breeding colonies of pinnipeds, pathology observed in carcasses, and experiments with captive seals all have shown associations

between reproductive failure of females and exposure to certain organochlorines or mixtures of

organochlorines. These generally take the form of

preimplantation disorders (thought to be due to

effects on endocrine physiology), spontaneous

abortions, or premature pupping. However, the

specific compounds or mixtures that may be responsible for the observed disorders, the physiological

mechanisms leading to the effects, the interactions

with or roles of disease agents, and the populationlevel significance and extent of occurrence of these

phenomena in most marine mammal populations

remain uncertain. If these gaps in knowledge are

not addressed, the causes of population declines,

including those involving endangered or threatened

populations and strategic stocks (in the sense of the

U.S. Marine Mammal Protection Act), are less

likely to be determined or recognized. The result

will be that management or regulatory measures are

not taken in a timely manner.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

7

Potential for Impacts of EndocrineDisrupting Contaminants

Exposure to endocrine-disrupting chemicals during

gestation, lactation, and adulthood is known to alter

reproductive function and development in

laboratory and domestic animals, humans, and freeranging wildlife species. Cause-and-effect

relationships between endocrine disruptors and

altered reproductive function or development in

marine mammals have not been established.

However, laboratory studies and research on other

wildlife, and the documented high tissue exposure

to some of these compounds in some pinnipeds and

cetaceans, suggest that effects may occur in marine

mammals. Resolving this uncertainty will improve

understanding of the possible effects on marine

mammal populations of chronic exposure to

pollution. 

Predicting the Risk to Individuals and

Populations Associated with Exposure to

Persistent Contaminants

There is much uncertainty in estimating the risk of

exposure to contaminants for individuals or

populations of marine mammals. Formal risk

assessment procedures have not been widely applied

in contexts involving marine mammals. However,

for endangered or severely depleted populations, the

death of even a single individual could negatively

influence the population’s survival prospects. The

uncertainty in estimating risk can be reduced by

using an iterative approach to risk assessment and

risk management. Discussion between the risk

assessors and risk managers must occur as

information is developed. This will require casespecific information on contaminant exposure and

effects, and risk characterization based on the

weight of evidence. Without a formal, integrated

process for evaluating contaminant risks, managers

and regulators will lack a coherent basis for

decision-making, and this will ensure substantial

scientific and public controversy.

Future Trends with Currently Known

Contaminants

Persistent ocean contaminants to which marine

mammals are known to be exposed include several

bioaccumulative organochlorines and their

metabolites, particularly certain PCBs and DDTs.

Although concentrations of some of these

contaminants have declined in some marine

mammal populations since certain countries placed

major restrictions on their production and use, their

future global distribution and flux remain uncertain.

This is particularly true because some

organochlorines continue to be produced, or are

stockpiled and in use in many parts of the world. In

addition, the effects of chronic, low-level exposure

to some of these chemicals are uncertain. Thus,

potentially harmful exposure to organochlorines

will continue for many years, and in some regions is

likely to increase. Information on projected usage

patterns and environmental fates of organochlorines

needs to be expanded, synthesized, and analyzed for

various regions. Uncertainties about effects also

need to be reduced to allow such projections.

Otherwise it will be difficult for policy makers and

regulators to assess likely future impacts on marine

mammals.

Future Trends with Less Widely

Recognized Contaminants

 It is uncertain which of the many new chemical

contamination problems on the horizon will have

serious impacts on marine mammals. Such impacts

are difficult to anticipate or prevent in the absence

of basic information on production, use, exposure,

and effects. There are an estimated 2,400 lipophilic

and persistent chemicals with potential to become

problems in the environment. There are many

additional chemical substances that are less

persistent but that have potential for chronic effects

on marine and coastal ecosystems. Among these are

the polycyclic aromatic hydrocarbons, non-organohalogen biocides, polymers and low molecular

weight monomers, and pharmaceuticals.

Eutrophication of coastal waters from anthropogenic

inputs of nitrogen and phosphorous compounds will

continue to cause major ecosystem changes, with
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

8

uncertain effects on marine mammals. An increase

in algal blooms and biotoxin poisoning of marine

mammals appears to be one alarming consequence.

PRINCIPAL CONCLUSIONS AND RECOMMENDATIONS

The summary list of principal conclusions and

recommendations (Table 1) described below is

based on common threads and major elements in the

working group reports. These conclusions and

recommendations were developed by the report

editors and circulated to each workshop participant

for review and comment with a draft of the full

report. A broad range of opinions can be expected

on the relative importance of some of these topics,

and they are therefore not listed in any particular

order of priority. The full working group reports

(Section III) provide detailed explanations and

greater specificity.

(1) Integration of Multiple Approaches

A greatly improved understanding is needed of the

linkages between specific chemical exposures (both

type and amount) and endpoints of concern (e.g.,

impaired health, immunosuppression, and reproductive disorders). Integration of laboratory, captive

animal, and field studies was a consistent theme of

workshop deliberations. No single approach is

likely to be adequate for resolving the critical

uncertainties that arise in relation to contaminants

and marine mammals. Thus, there is a need for

multidisciplinary studies that integrate physiological, behavioral, reproductive, clinical, pathological,

and toxicological data, with the ultimate goal of

linking immune status, health, reproduction, and

survival of individuals to trends observed or predicted at the population and ecosystem level. Doseresponse relationships are critical, and quantification of these relationships should be a goal of all

studies of individuals (see No. 17). Surrogate

species can be particularly useful in studies of

mechanisms of action (see Nos. 9 and 11).

(2) Stable Support for Critical LongTerm Programs with Increased Emphasis on Wider Collaborations

Long-term monitoring and research programs

provide consistent, accumulative information that is

essential for understanding trends and impacts of

contaminants in marine mammals. Established

ongoing programs should be viewed as long-term

investments that are necessary for the effective

assessment and management of marine mammal

populations. They should remain a high priority of

sponsoring agencies and organizations and be given

firm support. New efforts and enhancements to

existing programs should also be implemented with

assurances for long-term, stable support. Examples

of ongoing programs appear in the report by Rowles

and Thorsteinson (Appendix C). In addition, the

study of contaminant effects is well-established in

the fields of medicine and environmental toxicology. Marine mammal scientists should be encouraged to collaborate with programs in these fields. In

the United States, such links could be established

via programs formally co-sponsored by the National

Institutes of Health, the Environmental Protection

Agency, the Marine Mammal Commission, or the

National Marine Fisheries Service. Numerous other

avenues exist for developing collaborations, assuming that adequate support is made available by the

relevant agencies involved in marine mammal

conservation. Marine mammal science is an almost

uniquely international discipline. Collaboration

between international programs is greatly encouraged. 

(3) Long-Term Interdisciplinary Studies of Local Populations
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

9

Long-term interdisciplinary studies provide opportunities to measure contaminant exposure, monitor

the health and immune responses of individuals, and

relate findings to population-level trends, all in the

context of knowing a great deal about the animals’

life history, distribution, abundance, population

dynamics, and demography. Long-term studies of

local populations hold out the possibility of obtaining insights on contaminant effects, grounded in

observations from nature. In this context, the

population of bottlenose dolphins centered in

Sarasota Bay, Florida is probably the best studied of

all cetacean populations in the world. Most individuals in the population have been caught, marked,

sampled, and released, many of them repeatedly,

since 1970. Although the Sarasota Bay situation

may be unique, there are similarly important opportunities with at least a few other wild populations.

For example, similar studies of bottlenose dolphins

are underway in Scotland, and long-term studies are

ongoing with the northern right whale population

off eastern North America, the beluga population in

the St. Lawrence River, the killer whale population

in inshore waters of Washington and British Columbia, Florida manatees, California sea otters, and the

California sea lion population that breeds on San

Miguel Island, California. Other populations are

subject to studies that provide a great deal of information about feeding ecology and other important

subjects — for example, studies of the “bachelor”

group of Pacific walruses that haul out on Round

Island in Bristol Bay, Alaska. It is important that

these and similar programs continue to be supported

and that long-term tracking of the health, contaminant, and disease status of individuals be incorporated into data-collection protocols. Selection of

study populations should not be limited to those that

are depleted or threatened or that have experienced

a recent die-off. Any long-term longitudinal study

offers opportunities to assess the effects of chronic

pollution, and it is valuable to investigate effects

during periods of population decline, stability, and

recovery. 

(4) Compilation and Dissemination of

Information 

Existing systems for compiling, interpreting, and

disseminating data on the production, use, physical

and chemical properties, toxicology, and ecological

effects of persistent contaminants should be improved. It is currently estimated that there are

roughly 2400 lipophilic and persistent chemicals, of

which at least 390 are clearly toxic and bioaccumulative. In order to prevent long-term pollution

from these largely unknown chemicals, basic information about them needs to be made widely available. This will require enhanced international

cooperation, preferably within the existing framework of chemical contaminant programs, such as the

Existing Chemicals Program of the Organization for

Economic Cooperation and Development, the

Program on Persistent Organic Pollutants of the

United Nations Environment Programme, and the

International Program on Chemical Safety. The

Marine Mammal Commission should facilitate a

dialogue among U.S. government agencies and

relevant international bodies with the goal of ensuring that a greater amount of basic information on

contaminants is available. Such information is

crucial for anticipating future problems associated

with chemical contaminants in the marine environment. Contaminant categories of particular concern

in relation to marine mammals include

organometallic compounds and persistent, toxic,

bioaccumulative compounds not on the standard

persistent organic pollutants (POPs) list but that

have been used or produced in large quantities, such

as polychlorinated naphthalenes and polychlorinated

diphenyl ethers. Other contaminants of concern that

could present a risk to marine mammals include

non-persistent chemicals with high bioaccumulation

potential and heavy or widespread use, chemicals

that contribute to coastal eutrophication, polymers

and low molecular weight monomers, and a variety

of chemicals that may cause endocrine disruption.

(See also No. 5.) 
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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(5) Monitoring Environmental Loads and

Ongoing Inputs of Persistent

Contaminants

In spite of encouraging evidence that levels of some

compounds (e.g., PCBs, DDT) have declined in

some areas (e.g., the North American Arctic, western Europe), production and inputs to the environment continue in areas such as the former Soviet

Union (PCBs, perhaps until very recently) and many

tropical countries (DDT and other organochlorine

pesticides). This situation creates an ongoing need

for global-scale monitoring. Monitoring contaminants in tissues of marine mammals is of direct

importance for issues related specifically to this

group, but more sensitive detection of contaminant

trends in the marine environment in general requires

monitoring of other ecosystem components. Attention needs to be paid not only to analyses of water

and biological samples, but also to identifying

emission sources, transport mechanisms, and transport pathways, and to calculating environmental

loads. (See also No. 4.) 

(6) Universal Protocols 

Tissues are sampled and biomarkers measured from

biopsies of living marine mammals and from the

fresh carcasses of stranded, bycaught, or hunted

animals. Universal protocols should be adopted for

sample collection and storage, laboratory analytical

procedures, and data reporting. Sample collection

should include specified basic data and supporting

documentation. Tissue specimens should be archived under consistent conditions in dependable,

long-term programs. As analytical techniques are

developed, data comparability between and among

laboratories should be assured on a global scale.

Laboratories should adopt a performance-based,

quality-assurance approach that incorporates standard reference materials (SRMs) and inter-laboratory comparisons. Existing SRMs should be analyzed, and, if necessary, new SRMs developed for

emerging chemicals. Quantitative information

should be generated for as many compounds as

possible in order to provide robust data sets for

future use. Protocols should stipulate quantitation

of a minimum number of compounds of persistent

contaminants in order to enhance the comparability

of data sets for purposes of risk assessment and

trend analysis. Existing analytical techniques

should be used to the fullest to identify all

anthropogenic chemicals in tissues, and thus expand

the number of existing and new chemicals known to

accumulate in, and potentially pose threats to,

marine mammals.

(7) Use Formal Risk Assessment

Procedures to Evaluate Threats 

Formal risk assessment procedures should be

adapted and used to evaluate threats of contaminants

to specific marine mammal populations. The

Ecological Risk Assessment approach established

by the U.S. Environmental Protection Agency

couples risk assessment to risk management in a

process that can be iterative. This process begins

with problem formulation: contaminant sources,

fates, and pathways are described; contaminants of

concern and their modes of action are defined; and

receptors of concern are identified. A risk assessment would describe specific hypotheses to be

tested and measurements that can be made to evaluate endpoints of concern in the analysis phase. Risk

characterization, which follows the analysis phase,

uses information on exposure and effects to evaluate

the risk, generally using a “weight of evidence”

approach. This approach balances the information

on effects, usually obtained from mechanistic

laboratory studies, against the results of captiveanimal or field studies. Uncertainty about aspects of

risk assessment should be clearly discussed. Discussion should include the ecological significance

of the risk, how effects on individuals have been

extrapolated to effects on populations, and how

risks from contamination have been compared to

risks from other stressors. The ideal outcome of

risk characterization is identification of threshold

concentrations, above which risk becomes significant and risk management is required. 

(8) Use of Rehabilitated and Captive

Marine Mammals and Associated

Databases

Marine mammals held in captivity that are fully
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

11

rehabilitated or on display are an under-used resource for the study of contaminant impacts on

physiological processes and health. These animals

are likely to be exposed to contaminants in routine

daily rations of marine products, at least at low

concentrations, and are likely to have contaminants

in their bodies. Clinical measurements of blood

chemistry and hematology, and detailed information

on health, reproduction, and survival are routinely

recorded for these animals. Provided that care is

taken in the design of sampling to avoid confounding effects of prior injury, disease, or response to

captivity, use of this resource may provide basic

insight about the variability in and relationships

between contaminants and basic health and physiological processes, biomarkers, reproduction, and

survival. Such insight could prove critical to interpretation of contaminant impacts on wild marine

mammal populations.

(9) Use of Surrogate Animal Models

The extensive literature on mammalian toxicology

provides many examples in which studies of surrogate species have been used in place of humans. A

similar approach can be useful for marine mammals.

Studies of surrogate species can provide insights

about mechanism of action, the comparative risks

presented by different chemicals, and dose-response

relationships. Experimental control makes it possible to eliminate confounding factors and reduce

variability within treatment groups, thus providing

the statistical power necessary to detect effects. The

greater availability of species-specific reagents, and

the ability to carry out invasive studies, represent

additional advantages of using surrogate models.

The selection of an appropriate surrogate model

depends on the question being posed and the endpoint being assessed. The usefulness of information

generated from studies of surrogate models will

depend upon certain assumptions and extrapolations

which require critical evaluation at all stages of the

research. (See also No. 1.) 

(10) Controlled Experimental Studies to

Address Critical Questions1

The need for controlled experiments to answer

critical questions about the effects of contaminants

on marine mammals was generally acknowledged

by all working groups at this workshop. Some of

the critical questions regarding impacts of even the

most commonly observed persistent contaminants in

marine mammals have been asked for more than 25

years, without clear answers. For example, premature pupping of wild California sea lions in the late

1960s and early 1970s was associated with high

concentrations of DDE in tissues, but other confounding factors were also observed. A cause-andeffect relationship between DDE and premature

pupping has never been established. Today, we

1

Editors’ note: The recommendation that non-lethal

experimentation on captive marine mammals be

employed to help resolve critical uncertainties was made

in every working group report. This recommendation

was discussed during plenary sessions with few

objections raised from the floor. During review of the

full draft report, two participants voiced personal

opinions that the use of surrogate species and a “weight

of evidence” approach would suffice in place of captive

experiments under any circumstance. One participant

questioned the feasibility of captive experimentation.

Recognizing that there are differing views about the

appropriateness of controlled experimentation with either

captive or free-ranging marine mammals, agencies with

management and regulatory responsibility should

establish procedures for deciding when experimentation

is warranted. This will help to minimize public

controversy, and to prevent environmentally costly

delays,. Such procedures would identify all stakeholders

(most of whom will undoubtedly share concern about the

impacts of contaminants on marine mammals) and ensure

that their views are appropriately represented in the

decision-making process. The procedure would also

create a mechanism or mechanisms for ensuring that

experiments are humane and optimally designed. In the

experiments on captive harbor seals that were carried out

in The Netherlands, for example, the “contaminated”

source was market fish, and observed reproductive effects

were reversible once the seals were placed back on a less

contaminated diet.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

12

recognize that DDE is likely present, at least in trace

amounts, in virtually every marine mammal in the

world. Since premature pupping in the California

sea lion was first observed, it has been learned that

elsewhere DDE co-occurs at high levels with other

contaminants in some populations of marine mammals. Various reproductive lesions and susceptibility to diseases have also been observed in these

populations. Yet we still do not know definitively

what role this ubiquitous contaminant actually plays

in marine mammal reproductive disorders or diseases.

One reason for this chronic uncertainty is that

it has been difficult to obtain funding, facilities, or

authorization to carry out controlled experiments on

captive marine mammals. Without the highly

convincing kind of evidence that only experimentation can provide, the uncertainty and debate regarding cause-and-effect relationships and necessary

mitigation are bound to continue for decades.

Meanwhile, the health of individual animals and the

persistence of species and populations may be in

jeopardy. Risebrough’s personal account (Appendix E) illustrates how uncertainty as to whether

DDE was responsible for eggshell thinning in birds

was resolved in part by simple experiments in

captivity. Experiments contributed to a ban on the

use of the parent compound, DDT. Had such

measures not been implemented at the time, a likely

outcome would have been the extinction of many

North American bird populations and species.

As emphasized in the report of the Future

Trends Working Group (Section III of this volume),

marine mammals will face a widening array of

“new” chemical compounds in the immediate

future. Many of these contaminants could adversely

affect marine mammals directly, or they could affect

other components of the food webs on which marine

mammals depend. Most workshop participants

agreed that a two-pronged strategy should be followed in confronting this reality. First, procedures

similar to those currently being developed by the

U.S. Environmental Protection Agency should be

developed and applied globally to assess the effects

of “new” chemicals on the survival and productivity

of representative ecosystem components. Such

assessments should be made before these chemicals

are mass produced. Second, when there is uncertainty about a chemical’s effects, and it is determined that a delay in resolving that uncertainty

could jeopardize the survival of a marine mammal

species or population, it may be necessary to conduct experiments with captive marine mammals.

Such experiments would involve non-lethal exposures to doses of contaminants similar to those

experienced by some wild populations. The studies

would need to be well justified and well designed.

Design would have to include power analysis to

ensure that the results would be conclusive.

(11) Understanding Processes Linking Exposure to Effects

Understanding the linkages between contaminants

and the health, immune system, or reproductive

fitness of individual marine mammals at the cellular

or molecular level is most likely to come from

laboratory studies. Cell culture and in vitro techniques can contribute by providing species-specific

data on topics such as toxic equivalency. In so far

as it is possible, toxic equivalencies should be

developed and validated using the cell lines of the

marine mammal species of interest. Severe Combined Immune Deficient (SCID) mice and other

laboratory mammals can be used for the detailed,

invasive types of experimentation needed to improve understanding of the biochemical processes

linking exposure and effects. Data from such

studies can be employed to strengthen (or weaken)

arguments involving the extrapolation of in vitro

results to whole organisms. Semi-field trials and

epidemiological studies of wild populations (using

biopsies of free-ranging animals, blood drawn from

animals that are captured and released, and specimens salvaged from strandings, bycatch, and subsistence hunts) can be used to validate the inferences

based on laboratory evidence or extrapolation from

model or surrogate species. A “weight of evidence”

argument can be established on the basis of these

different types of studies. A difficulty that will arise

in evaluating the evidence for some marine mammal

populations is that, under protection or well-regulated exploitation, they are in the process of recovering and experiencing phases of rapid population
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

13

growth. This can mask or confound the evidence

for contaminant-related effects on population

dynamics and abundance, whereas such effects may

be more readily discernible in depleted populations.

(12) Destructive Sampling of Tissues for

Biomarkers and Contaminants

The usefulness of “biomarkers” has been widely

discussed, but their application and validation for

marine mammals remain at an early stage of development. Biomarkers can be used to assess chemical

exposure and with further development should, in

the future, be capable of predicting effects in marine

mammals. Biomarker studies should be included

with other types of contaminant-related research on

marine mammals. The results of such studies need

to be closely linked to information on contaminant

burdens and exposures, and on physiological and

life history traits. Some widespread contaminants

and metabolites have low potential for

bioaccumulation and are short-lived, but their

ingestion or inhalation by marine mammals may be

a cause for concern. For assessing exposure to such

compounds, biomarkers may be very useful. Understanding the mechanisms of biomarker production

is critical, but at least three key distinctions should

be made: (1) biomarkers that simply demonstrate

exposure vs. those that show or predict effect; (2)

biomarkers of persistent vs. ephemeral contaminants; and (3) biomarkers for single vs. multiple-chemical stressors. Biomarkers for marine

mammals should be sensitive, rapid, inexpensive,

and field-adaptable. Similarly, non-destructive

sampling is often the preferred approach for collecting contaminant exposure data from marine mammals. However, samples that can be collected

non-destructively are often not from the target site

for the contaminants of concern. This situation is

not unique to marine mammals. The same dilemma

can arise in studies with humans, and the relevant

literature on humans and other mammals should be

directly applicable. The primary issue of concern is

the validation of a measurement in a tissue, such as

blood, as a reliable surrogate for a target site in an

internal organ. Validation studies will be necessary

to increase the value of non-destructive samples as

surrogates for target sites in marine mammals.

(13) Expansion of Sampling and

Monitoring Programs to Include

Histopathology, Immunotoxicity, and

Life History Information

Some contaminants to which marine mammals are

exposed, including organochlorines and trace

metals, are known to affect the immune systems of

other species. It is uncertain to what extent they

may also affect the immune systems of marine

mammals. There is sufficient reason for concern,

however, and long-term programs for sampling

marine mammals should include protocols for

obtaining samples and data to support investigations

of histopathology and immunotoxicology. In all

cases, it is important to emphasize the need to

collect associated life history information. The

latter is essential for proper interpretation of findings.

(14) Selecting Model Species of Marine

Mammals

It is unrealistic to expect that adequate studies will

be conducted on most marine mammal species.

Therefore, model species must be identified and

employed in relevant studies. It was generally

agreed that the most appropriate marine mammal

species to use as study subjects are those for which

considerable information is already available about

population dynamics, life history, and physiology;

that are in captivity or otherwise easily accessible;

and that are already involved in related ongoing

studies. Other factors to consider are the feasibility

of obtaining high-quality samples in large enough

numbers to ascertain sources of variation; whether

the species occurs across a gradient of habitats

(highly polluted vs. relatively pristine); and conservation status (endangered, threatened, depleted,

etc.). Among the cetacean species that come the

closest to meeting these requirements are the bottlenose dolphin, harbor porpoise, and beluga whale.

The 1995 International Whaling Commission

workshop on contaminants and cetaceans also

identified these as suitable species for study. Captive studies of baleen whales are out of the question,
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

14

but given the considerations listed above, the bowhead whale is probably the most suitable candidate

for a model baleen whale in the United States. This

is due to the availability of specimens from the

subsistence hunt by Alaska natives and the relatively solid background of life history and other

information on the species. On a global scale, the

minke whale may serve as an even more useful

model, because of regional variations in ichthyophagy and availability of specimens from hunting.

The harbor seal and gray seal are the best candidates

among phocid seals, whereas the California sea lion

and northern sea lion are the prime candidates

among otariids. The polar bear can be studied

directly. Although sirenians were not generally

seen as a high-priority group in the context of

typical organochlorine contaminants, the Florida

manatee is obviously the best model sirenian because of the well-organized stranding program,

number of captive individuals, and ongoing life

history studies. Because sirenians feed near the

bottom in coastal and inland waterways and are

herbivores, their exposure to contaminants may

include less widely recognized chemicals that are

more prevalent in such ecological contexts. The

mink is a widely used experimental animal, and it

can be used as a surrogate for the closely related

marine mustelids (sea otter and marine otter). Even

among mustelids, however, mink are known to be

exceptionally sensitive to certain contaminants.

(15) Selecting Model Contaminants

The 1995 workshop on cetaceans and contaminants

sponsored by the International Whaling Commission identified three categories of chemicals according to how regularly they had been monitored in

cetaceans. It was suggested that the criteria for

selecting model compounds for priority monitoring

and study should include levels of production,

potency of bioaccumulation, and toxicity. The

present workshop emphasized the need to place

highest priority on chemicals with known adverse

effects and/or that marine mammals are known to be

exposed to. Based on current knowledge, PCBs,

DDT and metabolites, other organochlorines,

butyltins, and a few trace elements are the most

obvious candidates. The mutagenic and genotoxic

effects of PAHs warrant study in exposed populations.

(16) Complex Mixtures

All marine mammals have body burdens of many

different contaminants, in variable amounts, stored

or circulating in different organ systems. Although

in standard toxicological studies effects are generally related to a single chemical, marine mammals

in the wild are exposed to complex mixtures rather

than to single chemicals. Effects from exposure to

multiple contaminants may be synergistic or antagonistic. For this reason, experimental exposures

should include complex mixtures that mimic as

closely as possible the types of exposure experienced by animals in nature. However, exposures to

complex mixtures should not be conducted until

dose/response relationships for the individual

chemicals involved are understood. Care should be

taken to avoid conclusions based solely on in vitro

exposures, which may be more abrupt and thus

exaggerated in their effect, compared with the

gradual and perhaps lower-dose exposure experienced by the whole organism in nature. However,

it should also be considered that some single substances may need to be studied in isolation in order

to assist managers and policy-makers in decisions

about production, use, and fate of specific chemicals.

(17) Dose-Response Relationships

Ideally, the effects of contaminants should be

understood well enough to predict responses from

specific doses, including likely “safe” or no-effect

levels of exposure. Analyses of the dose-response

relationship must be pursued on a species-by-species, contaminant-by-contaminant basis. Experiments and sampling designs should require that

exposure be controlled or at least measured, and that

potentially confounding factors (e.g., age, sex,

reproductive status, nutrition, etc.) be taken into

account as completely as possible when investigating dose-response relationships. 

(18) Endocrine Disruption

In recent years, endocrine disruption has become
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

15

recognized as a potentially widespread, insidious

conservation problem. Although evidence that

hormonal or developmental dysfunction in marine

mammals is linked to contaminant exposure has

been slow to accumulate, some common contaminants of marine mammal tissues (such as several of

the organochlorines) are known to affect the endocrine systems of other species. A precautionary

attitude requires, at a minimum, that the potential

for endocrine disruption in marine mammals be

regarded as a serious possibility and be subject to

aggressive research and evaluation. A “weight of

evidence” approach should be used in judging

whether measures should be taken to reduce exposure out of concern about this danger. Systematic

appraisal of a number of morphological and other

endpoints of endocrine disruption should be incorporated in routine marine mammal stranding and

health evaluations (see the report of the Working

Group on Endocrinology and Reproduction in

Section III). Trans-generational effects in longlived species like marine mammals may be particularly difficult to discern without incorporating such

appraisals in ongoing studies.

(19) Understanding Blubber Physiology

and Estimating Total Body Burdens of

Lipophilic Contaminants 

Physiological condition affects the distribution of

lipophilic contaminants in the bodies of marine

mammals. Further research on lipid dynamics is

required to improve understanding of the processes

determining this distribution (i.e., how lipid dynamics and physiological demands affect circulating

levels of contaminants that ultimately reach target

sites of action). Most published reports refer only to

concentrations of contaminants in blubber. Concentrations in muscle or other tissues are rarely mentioned. The ability to estimate total body burden is

important for determination of exposure factors in

risk assessment. Estimating the total body burden

of contaminants requires not only information on

distribution, but also estimates of the total amount

of blubber, muscle, and other tissues.

(20) Statistical Power in Experimental

Designs and Sampling Designs

Regardless of whether a contaminant study is to be

conducted in the laboratory or the field, it is essential that hypotheses be clearly formulated and that a

statistical model be developed to determine the

appropriate sample size before the experimental or

sampling protocol begins. It is of no benefit to study

a sample that is too small for statistically valid

results. Nor is there any benefit in sampling more

animals than is necessary. In the laboratory, standard statistical methods of determining significance

and power can be applied. In the field, it might

prove necessary to adapt the mathematical models

of epidemiology to understand the impacts of

contaminants on whole groups of animals. This

would involve stratification by age, sex, reproductive condition, season, location, and other factors.
16

Table 1. Principal Workshop Recommendations

C Increase Integration of Multidisciplinary Laboratory, Captive Animal, and Field Studies.

C Provide Stable Support for Critical Long-Term Programs and Increase Emphasis on Wider

Collaborations in the Environmental Health Sciences.

C Include Components on Contaminants and Health in Ongoing Long-term Population and Life History

Studies of Marine Mammals.

C Enhance International Cooperation and Improve Systems for Compiling, Interpreting, and Disseminating Data on Persistent Contaminants in Marine Ecosystems. 

C Monitor Environmental Loads and Ongoing Inputs of Persistent Contaminants to Marine Ecosystems

on a Global Scale.

C Follow Universal Protocols in Contaminant Sample Collection and Storage, Laboratory Analytical

Procedures, and Data Reporting and Maximize the Number of Contaminants Identified

C Use Formal Risk Assessment Procedures to Evaluate Threats of Contaminants to Marine Mammal

Populations. 

C Use Marine Mammals that are in Captivity for Display, Research, or Rehabilitation, and their

Associated Databases, for Insights about Contaminants and Health, Physiology, Reproduction, and

Survival. 

C Use Experiments with Surrogate Animal Models to Provide Insights about Mechanisms of Action,

Comparative Risks Presented by Different Chemicals, and Dose-Response Relationships.

C Conduct Controlled Experimental Studies on Captive Marine Mammals to Address Critical Questions.

C Increase Understanding of Processes Linking Exposure to Effects at Cellular or Molecular Levels.

C Continue to Develop Biomarkers and Validate Results of Non-Destructive Contaminant Sampling in

Exposure Studies.

C Expand Sampling and Monitoring Programs to Include Histopathology, Immunotoxicity, and Life

History Information. 

C Select Model Species of Marine Mammals for Intensive Contaminant Studies on the Basis of

Availability, Feasibility, and Background Knowledge of Biology and Habitat Use.

C Select Model Contaminants for Study Based on Levels of Production, Potential for Bioaccumulation,

Toxicity, and Suspected or Known Adverse Effects on Marine Mammals.

C Study Effects using Complex Mixtures that Closely Mimic the Types of Exposure Experienced by

Marine Mammals in the Wild.

C Determine Dose-Response Relationships.

C Evaluate the Potential for Endocrine Disruption, and Develop Protocols to Assess Morphological and

Other Endpoints of Endocrine Disruption as Components of Ongoing Studies.

C Improve Understanding of Blubber Physiology and Estimate Total Body Burdens of Lipophilic

Contaminants in Marine Mammals.

C Apply Rigorous Statistical Experimental and Sampling Designs in Field and Laboratory Studies.
17

Section III. WORKING GROUP REPORTS

Working Group on Immunotoxicology, Pathology, and Disease

Working Group Members: Beckmen, Carvan, De

Guise (Rapporteur), Fisher, Fournier, Gulland,

Haebler, Hall, Holladay, Lipscomb (Leader), Moore, O’Hara, and Thomas.

The topics addressed by this working group

fell into two areas: pathology/disease and immunotoxicology. Accordingly, two subgroups were

established, and each of them prepared a separate

report addressing high-priority issues. The overview statement from the entire working group is

presented below, followed by the subgroup reports.

Overview and General Recommendations 

The range of issues discussed in one or both subgroups included the following.

(1) The need to better understand the linkages

between specific chemical exposure and immunosuppressive endpoints. The strength of

reported linkages varies substantially. Knowledge of dose-response relationships would

help to establish cause and effect.

(2) The need for multidisciplinary studies on

selected well-known populations in order to

integrate toxicological, physiological, behavioral, reproductive, clinical, pathologic, and

population data. Such studies will improve

understanding of the role of exposure to

contaminants in clinical, pathologic, and

immunologic effects.

(3) The need to determine the predictive power of

molecular and cellular indices of chemical

exposure and effect in immunologic and

metabolic studies of persistent toxic contaminants. In vitro and in vivo mechanistic studies

are needed. Data to allow species-specific

understanding of toxic equivalency should be

developed using cell culture and in vitro

techniques.

(4) The need for tightly coupled laboratory,

captive-animal, and field studies linking

immunology, health, and disease.

(5) The need to link findings in individual animals with assessments of chemical impacts at

the population level.

(6) The need to expand long-term monitoring and

sample archival programs to include

histopathologic and immunotoxicological

samples and data, including life history information required for proper interpretation.

In summary, the potential impacts of persistent

ocean contaminants on marine mammal immune

function and health are of critical concern. Molecular, cellular, organismal, and population-level

processes need to be better understood. Relevant

data are best gathered and interpreted using carefully designed, multidisciplinary studies that link

laboratory, captive, and field studies.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

18

Pathology and Disease Subgroup Report

Subgroup Members: Beckmen (Co-Rapporteur),

Carvan, Gulland, Lipscomb (Leader), and Moore

(Co-Rapporteur) 

Issue Title: Current Understanding and

Future Directions of Research on the

Pathologic Effects of Persistent Ocean

Contaminants on Marine Mammals

Issue Description and Rationale:

Why Is This Issue Important? Some populations

of marine mammals are declining for reasons that

are poorly understood. Environmental contaminants

have been suggested as potentially important factors

in this regard. Knowledge of direct contaminantinduced pathologic effects and associated diseases

is limited in spite of the repeated documentation of

very high levels of a variety of xenobiotic chemicals

in tissues of many marine mammal species. The

effects of some of these chemicals are relatively

well understood in other animals, and they are likely

to be similar in marine mammals. Lesions can

indicate acute and chronic effects of contaminants

that are persistent either through bioaccumulation or

repeated exposure. Contaminant-induced lesions

have been shown to affect fecundity and survival of

individual animals of other species and, therefore,

may also affect the population dynamics of marine

mammals. Detection of unusual lesions can provide

an early warning of the effects of unrecognized

contaminants. In addition, such lesions may be

detected in individuals before a change could be

detected by routine stock assessments. Pathology

is, therefore, a critical tool for the conservation of

marine mammal populations.

What Is Generally Known about the Issue? High

levels of contaminants have been reported in a wide

range of marine mammal species. These levels vary

between and within species, spatially, temporally,

and stochastically. The trophic level of a population

and the extent to which it uses habitat in or near

areas of high-density human activity are 

important factors influencing contaminant burden.

There are no pristine areas unaffected by

anthropogenic contamination. Contaminants have

been associated with lesions in marine mammals,

but whether or not the contaminants caused the

lesions is uncertain. Some examples are uterine

stenosis and occlusions in gray seals and ringed

seals (Bergman and Olsson 1985); adrenal hyperplasia in gray seals (Bergman and Olsson 1985) and

beluga whales (Lair et al. 1997); a high incidence of

neoplasia in beluga whales (De Guise et al 1994b);

intersex conditions in polar bears (Wiig et al. 1998)

and beluga whales (De Guise et al 1994a); skull

lesions in gray and harbor seals (Bergman and

Olsson 1985, Stede and Stede 1990, Bergman et al.

1992, Olsson et al. 1992); and skin/integumentary

lesions in gray, ringed, and northern elephant seals

and sperm whales (Bergman and Olsson 1985,

Beckmen et al. 1997, Jauniaux et al. 1998).

What, in General, Needs to be Determined to

Resolve the Critical Uncertainties? Convincing

evidence is needed demonstrating a cause/effect

relationship between contaminant exposure to the

development of specific lesions in free-ranging

marine mammals, assuming that such relationships

exist. This requires that other potential etiologies be

fully considered and that accurate determinations of

exposure be made. The interrelationships need to be

determined among systemic and target-organ exposure, tissue burden and distribution, body condition,

and clinical and pathologic effects. The validity of

toxico-kinetic and pathologic extrapolations from

laboratory animals to marine mammals must be

further investigated.

What Are the Likely Consequences If These

Issues Are Not Addressed? Failure to gain an

understanding of the effects of contaminants on

individuals and populations will render scientists

unable to inform and advise policy makers and

managers. This will have negative impacts on

marine mammal health and population status as

contamination of the oceans continues. Ultimately,

loss of genetic diversity within species and loss of

species could occur.

Means to Resolve the Critical Uncertainties

Surrounding the Issues
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

19

In order to determine whether or not particular

lesions are induced by one or more contaminants,

studies are needed that are long-term, multidisciplinary, and well documented. Such studies need

to examine all likely etiologies systematically. It is

essential that studies have adequate controls and

sufficient sample sizes to address variables of

concern, such as age and reproductive status.

Groups of study subjects with documented high

levels of the contaminants in question should be

examined in parallel with comparable groups that

have low levels of these contaminants. Model

species should be selected to take advantage of

current knowledge, accessibility, and ongoing

studies. The success of this approach will rely on

obtaining as wide a dynamic range of contaminant

concentrations as possible (orders of magnitude if

possible). Because persistent contaminant concentrations tend to be relatively uniform on a regional

basis, collection of data on an inter-regional or even

global scale will probably be required.

The health status of living animals should be

monitored using physical examination, biopsy, and

blood-sample analysis during capture/release and

rehabilitation. Carcasses in good postmortem

condition from the same populations should receive

complete necropsies with full histopathologic and

appropriate toxicological assessment, along with

additional tests as indicated by the pathologic

findings. All of the available data for an individual

animal must be considered to reach a diagnosis.

Findings from many individuals can then be collated to assess significant trends. In this way,

lesions can be correlated with contaminant levels

and considered in the context of other variables,

thereby facilitating correct interpretation. Furthermore, these long-term, multidisciplinary studies

may facilitate recognition of changes that reflect

biological effects of previously unrecognized

contaminants.

Additional issues that can be addressed using

this approach include the following:

 

C Determining relationships among contaminant

exposure, immunosuppression, and outbreaks of

infectious disease.

C Potential recognition of chemical-specific

lesions.

C Determination of relationships among levels of

contaminants in blubber, blood, and target

organs, and correlation of these levels with

clinico-pathologic findings.

C Development and validation of practical indices

of exposure or effect (commonly referred to as

“biomarkers”).

C Validation of extrapolating from studies of

laboratory animals to marine mammals or from

studies of one marine mammal species to others.

The last item on the above list requires further

discussion. Some of the most persistent oceanic

contaminants are the halogenated aromatic hydrocarbons (HAHs ), which include PCBs, PCDDs, and

PCDFs (see Appendix F). Hazard and risk assessments of complex HAH mixtures have used a toxic

equivalency factor (TEF) approach, in which the

toxic equivalents (TEQs) of any mixture are equal

to the sum of the concentrations of individual

congeners (i) times their potencies (TEFi

) relative to

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, TEF =

1.0). TEFs have been used to estimate risk associated with many toxicological outcomes, including

immunotoxicity, hepatotoxicity, and carcinogenicity

(Andersen and Barton 1998, Vos et al 1997–98).

The toxicity of HAH congeners is speciesspecific, and so necessarily are TEFs, because

toxicity depends upon receptor-ligand interactions.

Several studies have demonstrated correlations

between TEFs derived by in vivo and in vitro

methods (Safe 1998a), which have been used to

develop toxico-kinetic models (Kreuzer et al 1997)

and estimate risk even at low levels of exposure

(Andersen and Barton 1998). Given the speciesdependent sensitivity to HAH, species-specific

TEFs for marine mammals have to be developed.

This can be done by using in vitro tools, such as

chemically responsive cell lines and recombinant

proteins. These can also contribute to the determination and quantification of complex interactions
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

20

such as antagonism and synergism. Such tools

would allow the analysis of metabolic enzyme

activity, binding of xenobiotics to cellular receptors,

and gene and protein structure.

Differences in metabolic enzyme activity

account for 90 to 95% of the interspecies variability

in response to xenobiotics. The remaining 5 to 10%

is related to the binding of chemicals to cellular

receptors which control enzyme levels (Nebert and

Weber 1990). TEF/TEQ data are currently being

generated for estrogenic compounds (Safe 1998b),

and this approach could be extended to other chemical classes that act through specific receptor-ligand

interactions.

Suggestions Regarding Existing

Monitoring and Research Programs

(1) Include Additional Data and Tissue Samples

When Marine Mammal Contaminant Samples

Are Archived. The National Marine Mammal

Tissue Bank, working in cooperation with the Arctic

Marine Monitoring and Trends Assessment Program, has stringent collection criteria and quality

control that are excellent for contaminant analyses.

However, other complementary data and samples

need to be collected in conjunction with the archived frozen samples. These should include life

history information, fixed tissues for histopathology, frozen serum, and frozen whole blood. 

(2) Provide Strong, Long-Term Support to

Stranding Programs. The structure of the Marine

Mammal Health and Stranding Response Program

is solid, but the program needs increased central and

regional support. Scientific study of stranded

animals during their humane rehabilitation, as

exemplified by operations at the Marine Mammal

Center in Sausalito, CA, can provide important

information that is otherwise difficult to obtain.

Programs that attempt this kind of study should be

encouraged and supported. 

(3) Encourage and Expand Long-Term Interdisciplinary Research That Includes Life History

and Health Studies. Long-term interdisciplinary

studies to monitor the health of free-ranging populations provide crucial information. Programs such as

the Sarasota Dolphin Research Project in Florida,

involving the capture and release of live animals

and detailed examinations of dead animals, should

be encouraged and expanded to other regions. In

addition, repeated sampling of catalogued individuals (i.e., animals that are naturally or artificially

marked so that they can be re-identified) in wild

populations can be extremely informative. Such

sampling needs to be integrated with long-term

ecological and demographic studies of those populations. For example, comprehensive studies using

individual identification have made it possible to

document reduced reproductive success in California sea lions on San Miguel Island and in North

Atlantic right whales. To determine the underlying

causes of such recruitment failures, the ongoing

studies of these populations will need to be augmented by multidisciplinary investigations of health

and disease. 

(4) Fully Use Information from Hunts and Bycatch. Subsistence hunts and fishery bycatch

should be fully used as sources of high-quality

samples.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

21

Immunotoxicology Subgroup Report

Subgroup Members: De Guise (Rapporteur), Fisher,

Fournier, Hall, Hollady, O’Hara, and Thomas

Issue Title: Relationships among Exposure

to Environmental Contaminants,

Immunotoxicity, and Individual and

Population Health Effects in Marine

Mammals

Issue Description and Rationale:

Why Is This Issue Important? In recent years,

large-scale epizootics have affected several populations of phocid seals (Geraci et al. 1982, Osterhaus

et al. 1988) and dolphins (Domingo et al. 1990,

1992, Lipscomb et al. 1994, 1996, Schulman et al.

1997). Many of the animals that died during these

disease outbreaks had high levels of environmental

contaminants in tissues (Hall et al. 1992, Aguilar

and Borrell 1994). Viral infections were strongly

implicated as the primary causes of these epizootics.

However, experimental animals chronically exposed

to PCBs are known to have increased susceptibility

to viral infections. A wide variety of viruses were

used in the experiments, including duck hepatitis

virus, a picornavirus (Friend and Trainer 1970),

murine leukemia virus, a retrovirus (Koller 1977),

and herpes simplex virus (Imanishi et al. 1980).

Accordingly, an immunosuppressive role of

organohalogens has been suggested to explain the

severity of the cetacean and pinniped epizootics (Eis

1989).

Contaminant-induced immunosuppression has

also been suggested as an underlying cause of

abnormal conditions observed in two other wild

marine mammal populations: the high incidence,

severity, and diversity of lesions, often associated

with opportunistic and mildly pathogenic bacteria,

found in dead beluga whales from the St. Lawrence

River (Martineau et al. 1988, De Guise et al. 1995)

and the prevalence of infectious disease as a mortality factor in southern sea otters (Kannan et al.

1998). Although many contaminants in the marine

environment, including organochlorines, heavy

metals, and polycyclic aromatic hydrocarbons

(PAHs), are well characterized as immunotoxicants

in laboratory rodents, immunotoxic effects on

marine mammals exposed to these agents have been

demonstrated to only a limited extent.

What Is Generally Known about the Issue?

Direct determination of the effects of environmental

contaminants on the immune systems of free-ranging marine mammals is difficult largely because of

logistical and ethical considerations. Approaches to

evaluating the effects have ranged from semi-field

and field studies to in vitro exposures and animal

models (Table 2).

Immune cells of beluga whales from native

hunts in the Canadian sub-Arctic were exposed in

vitro to heavy metals and organochlorines. The

proliferation of lymphocytes was significantly

reduced in cells exposed to concentrations of 10-5 M

of HgCl2 and CdCl2 (but not in cells exposed to

lower concentrations) when compared to unexposed

control cells (De Guise et al. 1996). These concentrations are within the ranges of mercury and cadmium found in tissues of free-ranging beluga whales

(De Guise et al. 1996). Similarly, the proliferation

of lymphocytes exposed to 20 ppm or more of PCB

138 and 50 ppm or more of p,p’-DDT, but not to

PCB 153, 180, or 169, or to p,p’-DDE, was significantly reduced when compared to unexposed control cells (De Guise et al. 1998). Interestingly, some

PCB congener concentrations which had no effect

on splenocyte proliferation when tested individually

(5 ppm) were found to reduce proliferation significantly when three of them were mixed (De Guise et

al. 1998). It is difficult to explain why the addition

of PCB 169, a coplanar congener that is usually

considered particularly immunotoxic, would have

reduced the toxicity of the mixture on beluga whale

cells. These data suggest that some organochlorine

compounds, at concentrations within the range of

those measured in the blubber of free-ranging St.

Lawrence beluga whales (Muir et al. 1990), have a

synergistic effect on beluga splenocytes. Overall,

the results of these in vitro assays demonstrate the

susceptibility of beluga cells to toxic compounds at

levels comparable to those found in some tissues of

wild animals. The synergistic effects of in vitro
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

22

exposure to mixtures of organochlorines, at levels at

which individual compounds have no effect on

immune function, raise questions regarding the

potential danger of environmentally relevant complex mixtures.

Animal models have been developed to simulate

exposure to environmentally relevant complex

mixtures and to evaluate the health effects of such

exposure. In one model, rats were fed highly

contaminated blubber from St. Lawrence beluga

whales and compared with control rats fed blubber

from much less contaminated Hudson Bay belugas

(De Guise et al. unpublished data). The rats that ate

highly contaminated blubber exhibited a slight

reduction of plaque-forming cells (PFC) in response

to sheep red blood cells (De Guise et al. unpublished data). In another model, rats were fed oil

extracted from highly contaminated Baltic Sea fish

and compared with control rats fed oil from much

less contaminated Atlantic Ocean fish (Ross et al.

1997). The rats that were fed highly contaminated

fish oil had impaired cellular immune responses, as

evidenced by decreased mitogen-induced lymphocyte proliferation in spleen and thymus, lower

CD4:CD8 lymphocyte ratios in thymus, and lower

viral infection-associated increase in natural killer

(NK) cell activity (Ross et al. 1997). These experimental models are useful in assessing possible

cause-effect relationships of exposure to environmentally relevant complex mixtures of contaminants

on the immune system.

The in vivo effects of exposure to environmentally relevant concentrations of pollutants were

demonstrated experimentally in a study of harbor

seals. The treatment seals were fed contaminated

Baltic Sea fish (e.g., daily intake of 1460 :g PCBs,

and 497 :g DDTs) and the control seals were fed

fish from the Atlantic Ocean that were less contaminated (e.g., daily intake of 260 :g PCBs and 102 :g

DDTs) (De Swart et al. 1994, 1996, Ross et al.

1996a,b). Results indicated impaired NK cell

activity, T-lymphocyte function, and delayed-type

hypersensitivity in the animals fed Baltic fish (De

Swart et al. 1995, Ross et al. 1995, 1996b). This

experimental design is very useful for investigating

the effects of exposure to environmental contaminants through food consumption. However, the

perinatal transfer of contaminants (through the

placenta and milk) that occurs in nature and that

may affect the highly sensitive, developing immune

systems of fetuses and neonates is not addressed in

such experiments.

Field studies, however difficult, are important

for evaluating the effects of chronic exposure to

environmental contaminants. In a study of freeranging bottlenose dolphins in Florida, regression

analysis found a correlation (r2

>0.75) between

decreased mitogen-induced lymphocyte proliferation and increased blood concentrations of several

organochlorines (including pentachlorinated and

hexachlorinated PCBs, p, p'-DDT, o, p'-DDE and

Table 2. Crude summary of current knowledge on immunotoxicology in laboratory and other

animals and in marine mammals

Other species Marine mammals

Presence of contaminants +++ +++

Immune effects of exposure +++ +

Consequences on individual +++ ?

Population consequences ? ? 

Key: +++ = abundant and reliable; + = limited; ? = too scarce to formulate an opinion
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

23

p, p'-DDE) in five individuals (Lahvis et al. 1995).

In a study of northern fur seal pups captured in

Alaska, a correlation was found between the mitogen-induced proliferation of blood lymphocytes,

along with other immunoassays and health parameters, and whole blood levels of organochlorines. 

There was an inverse correlation between

lymphocyte proliferation and the tissue concentrations of nine PCB congeners (Beckmen, unpublished data). This study also found that pups of

primiparous dams, the class with the highest levels

of organochlorines in blood, had significantly lower

antibody production in response to vaccination with

tetanus toxoid when compared to pups of old dams

with lower organochlorine concentrations in blood

(Beckmen, unpublished data). Taken together, these

data strongly suggest that environmental contaminants which are present in high concentrations in

tissues of marine mammals, and which are known to

have immunotoxic effects on laboratory animals,

also have immunotoxic effects on some marine

mammal species in the wild.

What, in General, Needs to Be Determined to

Resolve the Critical Uncertainties? The following

considerations provide a basis for concern about the

potential immunotoxic effects of contaminants on

marine mammals: (1) the evidence of immunotoxicity of environmental contaminants in rodents

and other species; (2) the presence of high concentrations of these contaminants in some marine

mammals; (3) the in vitro effects of these contaminants on marine mammal immune system cells; and

(4) the demonstrated immunotoxic potential of

environmentally relevant mixtures of contaminants

in animal models and in a small number of controlled in vivo exposures in pinnipeds.

There is, nonetheless, insufficient evidence to

establish a cause-and-effect relationship between

exposure to environmental contaminants and injury

to the immune system that might increase susceptibility to disease. Moreover, the significance to

populations of lowered disease resistance in individuals is uncertain.

What Are the Likely Consequences If These

Issues Are Not Addressed? If these issues are not

addressed, it will remain difficult or impossible to

assess the role of contaminants in epizootics and in

trends in marine mammal populations. The chronic

effects of contaminants on marine mammal immune

function will continue to be uncertain. As a consequence, our ability to recommend appropriate

regulatory measures and management policies will

be hampered.

Means to Resolve the Critical Uncertainties

Surrounding the Issues

In order to address the uncertainties identified

above, we recommend a combination of field

studies and carefully designed, controlled studies of

captive marine mammals to determine the effects on

the immune system of selected contaminants of

critical concern. Confounding factors such as sex,

age, nutrition, genetics, body condition, life cycle,

reproductive status (e.g., gestation, parity), blubber

condition (e.g., depth, lipid content), current disease, and previous exposure to pathogens should be

addressed in all studies. Sampling animals in the

field only allows the measurement of current immune function (i.e., the in vitro capacity of immune

cells to perform their immediate function). In

contrast, controlled studies of captive animals allow

evaluation of the organism’s potential to mount an

immune response, in other words, antigen processing, presentation, and collaboration between cells

resulting in an appropriate, specific response.

Multidisciplinary and multi-laboratory approaches

are highly recommended. The preferred approach

would include evaluations of at least the following

aspects: 

(1) Effects of Contaminants on Immune Function in Marine Mammals. The following relevant,

logistically manageable species are recommended

for use in captive-animal studies: harbor seal and

gray seal (to compare differences in susceptibility)

and polar bear. Studies involving cetaceans would

be costly and technically difficult, but they may be

needed. In vitro studies should be performed in a

specific context and designed to answer specific

questions. They cannot replace in vivo studies.

In conjunction with captive-animal experiments,
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

24

studies using well-characterized surrogate animal

models such as rats and mice should be used to

better define the links between exposure and response. Rodent-based TEFs should be used cautiously because they may differ among species, and

immune effects may not parallel enzyme induction,

as is indicated by the relative in vitro potency of the

PCB congeners in the beluga studies discussed

above. Species-specific TEFs should be developed

and validated for marine mammals using cell lines.

This would allow better comparison of experimental

results to the extensive literature on laboratory

animals. Also, surrogate animal models, such as

mink (for sea otters) and marine mammal immune

cell-reconstituted Severe Combined Immune Deficient (SCID) mice, would allow more invasive,

detailed, and mechanistic studies. Cellular and

molecular mechanisms of immunotoxicity of

organochlorines in marine mammals are unknown.

An appropriate way to investigate them would be to

examine mechanisms in animal models, and to

evaluate similarities and differences in these mechanisms in marine mammals. The effects of relevant

mixtures of contaminants also should be addressed.

For all experimental procedures, Good Laboratory

Practices Act protocols should be followed.

In order to improve understanding of immunology and other health-related parameters, as well as

to establish reference data, efforts should be directed toward obtaining information from captive

marine mammals. Public display facilities and

research-oriented institutions such as the Alaska Sea

Life Center could be used to study a variety of

species, including the beluga whale, harbor porpoise, bottlenose dolphin, killer whale, harbor seal,

gray seal, northern sea lion, polar bear, and sea

otter.

Field studies should be carried out to assess

potential immunotoxic effects on free-ranging

marine mammals. The recommended criteria for

choosing species for field studies include (1) selection of populations in nature that exhibit a gradient

of exposure to contaminants and (2) the ability to

sample a sufficient number of the animals to ensure

statistical power. The species listed in Table 3 are

recommended, based on documented exposure to

organochlorines, metals (mercury and cadmium),

and organotins. This is not a list of species of

concern, but rather a list of species that can be used

to investigate specific issues.

Table 3. Some recommended species for field studies

Documented exposure to:

Species Organochlorines Metals Organotins

Beluga whale Yes Yes Yes

Bottlenose dolphin Yes Yes Yes

River dolphins Yes Yes

Harbor seal Yes Yes Yes

Gray seal Yes Yes

Northern fur seal Yes Yes Yes

Sea otter Yes Yes Yes

Polar bear Yes Yes

Other coastal species Yes Yes Yes

Although West Indian manatees and northern

elephant seals do not necessarily meet the criteria,

they may provide opportunities to address particular

issues, such as those related to exposure to biotoxins

or effects of eutrophication.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

25

In designing studies, it is important to strive to

incorporate (1) immune-function and immuneresponse assays that are as complete as possible; (2)

sample sizes that ensure statistical power; and (3)

exposures that mimic environmental mixtures. To

investigate the relationships between organochlorines and immune function, measurements of

organochlorines in blubber and blood should be

employed as well as estimates of total body burdens.

(2) Consequences of Contaminant-Induced

Immune Impairment on the Health of Individual

Animals. In view of results with several other

species, it is reasonable to suspect that reduced

immune functions in marine mammals will decrease

the animals’ resistance to challenge by pathogens.

Nevertheless, such decreased resistance has never

been directly demonstrated for marine mammals.

Presenting a pathogenic challenge to one or more

marine mammals in a study context would raise

serious ethical and logistical problems. The possible need for such an experiment was discussed in

the subgroup, but no agreement was reached. In a

practical sense, any decision is likely to depend on

the weight of evidence, level of confidence, and

statistical power required in specific circumstances.

The use of marine mammal immune cell-reconstituted SCID mice could provide an alternative model

for testing the susceptibility of contaminant-exposed

animals to pathogenic challenge.

(3) Consequences of Contaminant-Induced

Impairment of Individual Animal Health to the

Population as a Whole. It would be useful to

generate baseline data at the population level. This

is most likely accomplished by long-term monitoring of some populations, with the goal to establish

normal values while accounting for seasonal variations, differences according to location, age, sex,

and life stage, and other potentially confounding

factors. This would make it possible to detect

changes in immune function in the population, or at

least in a portion of the population. When possible,

the population-monitoring tools should be Tier I

(screening) assays, including but not limited to

lympho-proliferation assays, immuno-phenotyping,

neutrophil phagocytosis and respiratory burst, and

NK cell activity. When feasible, it would be highly

desirable to follow cohorts through time.

Toxin-mediated immune suppression may cause

acute and chronic disease processes, including

epizootics, that have effects at the population level.

However, many other factors can influence immune

functions, such as food resources, climate, hormonal

status, and disease processes; these factors must also

be assessed. Natural history and population dynamics must also be integrated into such studies. This

requires well-designed protocols. In particular,

contingency plans should be designed to take

advantage of sampling opportunities during unusual

strandings or mortality events. Long-term field

studies should be designed to determine variables

affecting immune responsiveness.

Suggestions Regarding Existing Monitoring

and Research Programs

Some institutional programs exist for monitoring

mortality and contaminant burdens and for archiving tissue. One objective of the NMFS Marine

Mammal Health and Stranding Response Program

is to investigate biological linkages between chemical contaminants in the marine environment and

specific population health indices or parameters in

key populations. In addition, the National Institute

of Standards and Technology maintains the Marine

Mammal Tissue Bank, which ideally includes lifehistory information related to the tissues that are

being optimally maintained and archived for future

studies. The NMFS Marine Mammal Stranding

Networks continue to investigate and study stranded

marine mammals in the United States. As noted in

Appendix C, these include investigators supported

by the U.S. Department of the Interior who sample

sea otters, manatees, walruses, and polar bears

(species for which the Department of the Interior

has lead agency responsibility under the U.S.

Marine Mammal Protection Act). In addition, many

investigators throughout the world have tissue

collections, contaminant data, and stranding data.

The content and methods for maintenance of these

other collections vary.

Currently, there are no monitoring programs

relevant to immunotoxicological assessment. We
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

26

therefore recommend that the Marine Mammal

Health and Stranding Response Program and other

future monitoring programs include the key species

identified above as particularly relevant to immunotoxicology. In this regard, we support the ongoing

efforts to initiate the archiving of histological

samples and serum. Further, we recommend that

methods be developed for the cryo-preservation of

lymphocytes for analysis by current and future

techniques. We recommend that a standardized

suite of analytical procedures be adopted for measurement of immune function in monitoring programs. 

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Working Group on Endocrinology and Reproduction

Working Group Members: Addison, Béland, Bergman, DeLong, Gray, Mattlin (Rapporteur), Reddy,

Reijnders, Reynolds (Leader), Rolland, Rowles.

Overview and General Recommendations

To address the subject of effects on reproduction,

the group concentrated on early development and

premature pupping. A multi-faceted approach (i.e.,

a multidisciplinary approach, using a variety of

tools and perspectives) to assessing the potential and

success of marine mammal reproduction is essential,

and it must involve in vitro studies as well as studies

on captive, “semi-captive,” and free-ranging animals. The studies advocated by this group would

have optimal value when combined with assessments of life history parameters, reproductive

histories of individual animals, demography, immune function, pathology, and environmental

conditions (noise, productivity, trophic relationships, etc).

Long-term longitudinal studies of free-ranging

animals permit scientists to evaluate vital rates (e.g.,

natality, age-specific survival and reproduction).

These rates provide a context for understanding

population-level changes that may be associated

with environmental changes. In addition, longitudinal studies permit scientists to assess the effects of

chronic pollution (not just acute events) during

periods of population decline, stability, and recovery. Finally, such studies permit scientists to relate

behavior and reproductive success to contaminant

levels.

Recommendations of the working group include

the following:

C Develop international programs and collaborations to promote comparability;

C Conduct controlled experiments with captive,

semi-captive, and free-ranging animals, while

also remaining alert to opportunities for gaining

insight into aspects of species biology in other

ways;

C Use non-marine mammal surrogates in a sensible manner. Inasmuch as cellular and molecular

homologies exist across a wide range of taxa,

rodent models can provide insight into mechanisms and lead to identification of appropriate

biomarkers for marine mammal studies. However, such models are not necessarily appropriate for questions at the organismic or population

levels. In other words, the choice of a surrogate

depends on the question being asked;

C Establish priorities for chemicals and species to

be tested. It is impractical to investigate

endocrinological and reproductive effects for all

chemical contaminants and for all marine mammal species. Initially, model species should be

selected based on criteria such as ease of captive maintenance, status of knowledge about

physiology, breadth of distribution (including

whether the species occurs in a variety of habitats along a pollution gradient), feasibility of

obtaining quality samples, and status of stocks

(e.g., endangered, threatened, or strategic).

Among the species that emerge as logical models are the harbor seal, California sea lion,

northern sea lion, gray seal, bottlenose dolphin,

beluga, harbor porpoise, polar bear, walrus, and

sea otter. Priorities for chemicals should start

with those that have demonstrated adverse

impacts or a high likelihood of exposure and

bioaccumulation;

C Evaluate the appropriate tissues for exposures

and contaminant levels, and develop an understanding of toxicokinetics of transplacental

transfer; and

C Ensure adequate funding. New partnerships

should be forged to bring as many resources as

possible to bear on the critical issues. 

Issue Title: Understanding the Effects of Persistent (and Non-Persistent) Chemi-
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

30

cal Contaminants on the Reproductive

Potential and Reproductive Success of

Marine Mammals.

Likely Consequences If This Issue Is Not Addressed. Unless and until substantial progress is

made in resolving this issue, we will be faced with

the following general consequences:

(1) Problems will not be recognized in a timely

manner for investigation and mitigation; 

(2) Causes of population declines, including those

involving endangered or threatened populations

and strategic stocks (in the sense of the U.S.

Marine Mammal Protection Act), are less likely

to be determined; 

(3) The effects of new pollutants will not be detected until serious impacts or population declines have occurred;

(4) Without data from more common species of

marine mammals, no good models or validated

techniques will be available for application to

threatened, endangered, or strategic stocks that

are not accessible for study; and 

(5) Opportunistic approaches to address relationships between environmental changes and

population status will remain less focused. In

any event, such approaches can be costly and

generally provide less definitive results.

Means To Resolve the Critical Uncertainties

Surrounding the Issue. Three general approaches

to achieving the necessary understanding were

identified. The goals with all of these approaches

are to elucidate mechanisms and effects, and then to

use the insights gained to facilitate mitigation and

conservation.

General Approach 1: Disorders in the Estrous

Cycle before the Implantation Stage

Description and Rationale. Reproductive failure

in the early stages of the reproductive cycle may

have demographic consequences for any marine

mammal population. Comparative studies onharbor

seal populations showed that pup production in the

population in the Dutch part of the Wadden Sea was

low compared to that of other populations in the

Danish and Schleswig Holstein part of the Wadden

Sea (Reijnders 1980). Average pup production per

female in the Dutch population had declined by

approximately 30%. Toxicology studies revealed

that, of all the organochlorines analyzed, PCB levels

were significantly higher (by 5 to 7 times) in the

population with the lower reproduction rate. 

What Is Known. Because experimental studies had

provided evidence for negative effects of PCBs on

reproduction in other mammals, it was hypothesized

that PCBs were responsible for the observed low

reproduction in the Dutch Wadden Sea harbor seal

population. To test this hypothesis, an experimental

feeding study was carried out with two groups of

harbor seals, each group receiving a diet with a

different pollutant load. Pup production was significantly lower in the group receiving the more contaminated diet. Moreover, it was evident that the

reproductive cycle had been interrupted at approximately the time of implantation, accompanied by

temporarily lower levels of estradiol-17ß. This

phenomenon has not been investigated in other

marine mammal species.

Uncertainties About Pre-Implantation Disorders

and How to Resolve Them. Uncertainties about

pre-implantation disorders can be grouped under

three headings: (1) identification of which chemical

agents, if any, are responsible for the disorders; (2)

mechanisms leading to the observed effect; and (3)

occurrence and significance of pre-implantation

disorders in other harbor seal populations and in

other marine mammal species.

The experimental study (Reijnders 1986, Boon

et al. 1987) concluded that it was highly likely that

the observed effect was due to PCBs (although there

always remains the possibility that some of the

many other persistent contaminants present played

a role). The uncertainties are related to the question,

“Which congeners and/or PCB metabolites are the

responsible compounds?” It was suggested in this

study that these were the CYP 1A-inducer PCBs

(dioxin-like PCB congeners and Ah receptor

agonists). Three mechanisms were suggested: 

(1) enhanced steroid breakdown due to PCB-related
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

31

P450 enzyme induction;

(2) receptor interference at the target tissue or

carrier proteins due to PCB metabolites, particularly the binding of PCB methyl sulfones

(PCB-MSFs) to uteroglobin; and 

(3) interference with hormone synthesis and metabolic activity of the P450 enzyme system. 

Subsequent in vitro experiments suggested that

the first mechanism (i.e., increased hydroxylation of

estradiol leading to lower estradiol levels) was the

most plausible of the three possibilities. The uncertainty regarding the roles of the other two mechanisms noted above might be resolved by investigating whether the PCB-MSFs binding to uteroglobin

found in experimental laboratory mammals (e.g.,

rabbits) also occurs in harbor seals, and whether

aromatization of testosterone (e.g., in ovarian tissue)

is inhibited. Additionally, seal uterine tissue could

be tested for its hormone-binding capacity.

It is not known whether this problem occurs in

other harbor seal populations or in other marine

mammal species. In order to resolve this uncertainty, it will be necessary to assess whether other

marine mammal species are equally sensitive. The

first step would be to investigate hormonal cycles

(i.e., progesterone and estradiol) in other species,

either by analyzing archived plasma or serum

samples, or by carrying out studies with captive

animals. These investigations would need to be

followed either by feeding studies using model

species in captivity (e.g., ringed seal, or an otariid

and a small cetacean) or by field studies of populations that are exposed to differing amounts of

pollution. When choosing one or more populations

for field studies, the pollution levels in the presumed prey should be such that the daily intake by

the wild marine mammals is at least similar to that

of the two groups involved in the experiment, and if

possible should also include marine mammals from

areas with even higher levels in prey. Differences

in reproduction rates of the populations, and exposure levels as reflected in blood and blubber contamination, should also be clearly established.

General Approach 2: Premature Births in

Otariids

Description and Rationale. Premature births have

been recorded in California sea lions (DeLong et al.

1973), northern (Steller) sea lions (Pitcher and

Calkins 1981), and northern fur seals (Gilmartin et

al. 1976). Unfortunately, data on contaminant

levels were available only in the studies involving

California sea lions. Observed rates of prematurity

in California sea lions were as high as 20% in the

early 1970s (DeLong et al. 1973). High rates of

premature births decrease the potential for population growth, no matter what the species or the

location. It is therefore important to develop ways

of evaluating the role of new (and old) chemical

pollutants in influencing the rate of premature

births. The production and use of DDT continue in

some parts of Asia, and global PCB levels are not

expected to decline dramatically, particularly in

view of recent production and use in the former

Soviet Union and continued environmental inputs

and cycling (see Future Trends Working Group

Report). Long-range transport and equilibration of

contaminants could lead to elevated levels of

organochlorines in Southern Hemisphere otariid

populations and other marine mammals, possibly

leading to reproductive problems similar to those

experienced in California sea lions. An understanding of how, or if, organochlorines have influenced

premature births in California sea lions would

provide a valuable basis from which to begin investigating premature births in other otariids. 

What Is Known. An association has been documented between high organochlorine levels in

postparturient female California sea lions and

miscarriages or premature pupping during the last

two trimesters of pregnancy. The majority of

premature pups are born alive during the third

trimester, but all die within several hours of birth.

No significant differences have been found in serum

estrogen and progesterone levels between less-thanfull-term and full-term parturient females sampled

within 6 hours postpartum. The association of

organochlorines with prematurity is confounded by

the presence of diseases capable of inducing abortions: serological evidence of leptospirosis and

calicivirus has been found in both groups. Further-
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

32

more, the frequency of prematurity is higher in El

Niño years, indicating that the nutritional status of

the females also influences the probability of prematurit

y. 

Uncertainties and How to Resolve Them. The

greatest uncertainty is whether or not the premature

births are induced — directly or indirectly — by the

levels of organochlorines in the females. Too many

confounding variables (including age, nutrition, and

diseases such as leptospirosis and San Miguel sea

lion virus infection) are at play to allow a clear

cause-and-effect relationship to be inferred based

solely on the presence of contaminants and prematuri

ty (Addison 1989). This is a multi-factorial situation that will require differentiating among all

potential contributing causes, and should include

consideration of factors related to serology, age,

nutrition, disease, and genetics as well as contaminant exposure. 

Assuming that any effect of organochlorines is

mediated through the endocrine system, the first

requirement is to establish the normal hormonal

control of reproduction. This would require regular

analysis of circulatory hormones known (from other

animal studies) to be involved in the reproductive

cycle. The most useful measurement is probably the

ratio of progesterone to estradiol (Reijnders 1990)

because the former declines during pregnancy and

the latter tends to increase just before birth. Even

though the California sea lion has a life history that

allows collection of samples year-round from

potential representatives of both classes of females

(i.e., those that give birth prematurely and those that

reach full term), this kind of study would best be

done with animals in a captive breeding colony in a

controlled environment (including light regimes

similar to that experienced by the wild population).

The next step would be to validate the measurements in captive animals by analysis of wild animals at critical stages during the cycle. (The behavior of wild sea lions is such that it becomes difficult

to resample the same individual more than three or

four times. Furthermore, prematurity is difficult to

predict, so a relatively large number of samples

would have to be taken to ensure that a significant

number of females giving birth to premature pups is

available for comparison with ones giving birth to

full-term pups.)

A second set of “biochemical lesions” which

should be investigated is the possible interference of

organochlorines with aromatase, as well as ovarian

hydroxylation of estradiol (Reijnders, in press; see

also Section IV). This would require that the

normal cycle of aromatase as well as ovarian hydroxylati

on of estradiol activity be established in captive

animals, with eventual validation in field samples.

This would probably be more demanding than the

above approach using the progesterone:estradiol

ratio, because aromatase and hydroxylation measurements in vivo require injection of a suitable

substrate, followed by sampling of blood and

analysis of product after appropriate intervals. It

would be possible, but difficult, to carry out such

studies in the field.

The California sea lion is the best model

pinniped species for investigating the causes and

frequency of premature pupping. It is not threatened as is the northern sea lion. Also, it is well

represented in captivity, and there are several

captive breeding colonies (Asper et al. 1990).

Because of their natural history, adult female California sea lions are accessible on land year-round.

This creates the opportunity to make observations

and collect samples from individuals that ultimately

experience premature and full-term births. Although the current model is applicable only, or

primarily, to premature birth in pinnipeds, there is a

developing data set from the U.S. Navy’s population of bottlenose dolphins which could eventually

allow development of a model for evaluating reproductive failure in small odontocetes (Aguilar and

Borrell 1994, Reddy et al. 1998a,b, Reddy and

Ridgway 1995, Ridgway and Reddy 1995, St.

Aubin et al. 1996). 

General Approach 3: Indices of Reproductive and Developmental Functional Endocrine Toxicology in Marine Mammals

Description and Rationale. Exposure to

endocrine-disrupting chemicals (EDCs) during

gestation, lactation, and adulthood is known to alter
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

33

reproductive function in laboratory and domestic

animals, humans, and free-ranging wildlife species

(Colborn and Clement 1992). Although contaminant

exposure levels are often extremely high, few causeand-effect relationships have been established for

marine mammals. The approach described below is

cost-effective and takes advantage of existing

resources and infrastructure. 

What Is Known. Background information on this

topic can be categorized in three areas: (1) homolo

gy of endocrine function among mammals; (2) sex

determination and differentiation; and (3) results of

controlled experiments with rodents.

(1) Homology of endocrine function among mammals: from rats to marine mammals. Our recommendations (below) include not only studies on

captive, “semi-captive,” and free-ranging marine

mammals, but also surrogate mammalian species.

Rodent studies are recommended specifically to

address physiological, biochemical, cellular, and

molecular mechanisms of action of contaminants on

reproductive function. At the cellular and molecular

level, endocrine function is highly conserved. The

steroid and thyroid hormones of all mammals are

identical. The hormones act by binding to hormonal

receptors in the individual cells. These hormonereceptor complexes alter gene expression through

binding DNA at specific response elements on

specific genes. At this level, endocrine function is

highly homologous among mammals. However,

although the androgens induce male development

and function and maintain the reproductive tract in

males of all species, and estrogens and progestins

play similar roles in some aspects of female reproductive function in all mammals, some effects may

be quite species-specific. In addition, all mammals

may not metabolize or excrete EDCs in an identical

fashion. Hence, we propose that rodents be used to

identify mechanisms of action of contaminants, as

these mechanisms are likely to be conserved in

marine mammals. Effects studies in rodents are also

useful, but we must be aware of the limitations of

extrapolating from the laboratory to the field.

With respect to the EDCs, it is essential to

consider the unique sensitivity of the developing

reproductive system. In utero or perinatal exposure

to a contaminant can irreversibly alter reproductive

development in mammals in a manner that cannot

be anticipated from the effects seen in adults.

Chemicals that alter sex differentiation in rodents

may have similar effects in marine mammals, as

many of the basic mechanisms underlying the

developmental process are similar (Gray 1992, Gray

et al. 1998, Schardein 1993). For example, in most

mammals exposure to the synthetic estrogen diethylstilbestrol (DES), androgens, or progestins results

in morphological and pathological alterations of

reproductive function. DES treatment causes

cancer, infertility, and serious morphological abnormalities in all species examined. 

(2) Sex determination and differentiation. Sexual

differentiation, the development of the male or

female phenotype from an indifferent state, entails

a complex series of events. Genetic sex is determined at fertilization, and this governs the expression of the “male factor” and the subsequent differentiation of gonadal sex. At this stage of embryonic development, both sexes have bisexual potential. Following gonadal sex differentiation, testicul

ar secretions induce the further differentiation of the

sexual phenotype. The morphological and physiological development diverges, resulting in the

formation of the male and female phenotypes. The

development of phenotypic sex differentiation

includes persistence of either the Wolffian (male) or

Müllerian (female) duct system, differentiation of

the external genitalia, and sex differentiation of the

central nervous system (neurobehavior and neurological characterization of the central nervous

system through hormonal control). Other organ

systems, like the central nervous system and liver,

are sexually “imprinted” as well. The male phenotype arises due to the action of testicular secretions

— testosterone and Müllerian inhibiting substance.

In the absence of these secretions, the female

phenotype is expressed (whether or not an ovary is

present). In the human embryo, the onset of testosterone synthesis by the testis occurs 65 days after

fertilization. Testosterone induces the differentiation of the Wolffian duct system into the epididymi

s, vas deferens, and seminal vesicles, while its
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

34

metabolite, dihydrotestosterone (DHT), induces

development of the prostate and male external

genitalia. In the central nervous system, testosterone is metabolized both to estradiol and DHT, and

it has been suggested for some species that all three

hormones play a role in masculinization of the

central nervous system. In the rat, mouse, and

hamster, the aromatization of testosterone to estradi

ol is responsible, in part, for central nervous system

sex differentiation, while in certain other mammals

(e.g., the rhesus monkey) the androgenic (DHT)

pathway is essential. 

Aberrations of the chemical and genetic forces

that regulate sex differentiation in mammals are

relatively well understood because they are generally not lethal. Abnormal sexual development can

be induced by drugs, chromosomal non-disjunction,

and single gene mutations. There is an extensive

database on sexual differentiation in rodents, and it

is clear that the fundamental mechanisms of sexual

differentiation are the same in all mammals, although the timing of certain anatomical developments varies. During sexual differentiation, there

are a number of critical periods when the reproductive system is uniquely susceptible to chemically

induced perturbations. At these times, an inappropriate chemical signal can result in irreversible

lesions, whereas similarly exposed young adults

may only be transiently affected. It is also of

concern that some of the abnormalities may not be

expressed during fetal and neonatal life and only

become apparent after puberty. 

(3) Results of controlled experiments with rodents.

The biological effects seen in rodents exposed to

contaminants in controlled experimental settings can

provide guidance as to the types of effects that

might be seen in marine mammals exposed to the

same chemicals in the environment. Table 4 lists

the biochemical and whole-animal effects seen in

rodents exposed to organochlorines and other

synthetic chemicals, some of which have potential

to affect marine mammals. Table 5 lists effects seen

in male and female offspring that have been exposed to various contaminants of concern during

development, a uniquely sensitive time for exposure

to chemicals. With regard to Tables 4 and 5, it is

important to recognize that the indicated effects are

dose-dependent and that in many cases, it is not

known to what extent marine mammals encounter

these chemicals in amounts likely to cause many of

the effects listed.

Fetuses are particularly sensitive to TCDD,

PCBs, estrogens, and anti-androgens (such as p, p’-

DDE and DDT and phthalates). Effects can occur

in fetuses at dose levels that are orders of magnitude

below those that affect adult reproductive function.

In female rodents, treatment during perinatal life

with hormones or chemicals that disrupt hormone

function (e.g., estrogens, anti-estrogens, diethylstilbestrol (DES), androgens, phytoestrogens, and

estrogenic pesticides) can induce abnormal sex

behavior, persistent vaginal cornification (PVC),

and infertility via the Delayed Anovulatory Syndrome (DAS) (Tables 4 and 5). In male rodents,

potent estrogens like estradiol and RU-2858 antiestrogens, anti-androgens, and progestins alter

morphological sex differentiation and cause infertility. Environmental contaminants that are weakly

estrogenic, like the estrogenic pesticides, appear to

antagonize the action of testosterone on phenotypic

sex differentiation. Several chemicals like the

phthalates, vinclozolin, 
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

35

(Table 4)
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

36

procymidone, and linuron antagonize the action of

male sex hormones during differentiation and result

in malformations of the reproductive tract (e.g.,

hypospadias, undescended testes, agenesis of sex

accessory glands, and reduced anogenital distance)

(Tables 4 and 5). Sex differentiation in both male

and female mammals is altered by perinatal exposure to contaminants or treatments that lack or do

not display estrogenic or anti-androgenic activity

(Table 5). Such treatments include PCBs, TCDD,

the soil fumigant and nematicide dibromochloropropane (DBCP) and fenarimol (an aromatase

inhibitor), some neuroactive drugs, and the herbicide nitrofen. 

Means to Resolve the Critical Uncertainties. The

following elements need to be included in a strategy

for resolving uncertainties about endocrine disruption in marine mammals: establishment of baselines

on structure and function of reproductive and other

endocrine organs; establishment of linkages between contaminant loads and changes in structure or

function of endocrine organs; and separation of the

effects of contaminants on reproductive and other

endocrine functions from the effects of confounding

variables such as diet and disease. These elements

can best be achieved by (1) defining endpoints of

endocrine disruption that can be examined and

tested in marine mammals; (2) development of new

assays; (3) expanding sampling of target tissues for

maternal/fetal pharmacokinetics of contaminants;

(4) taking advantage of opportunities afforded by

existing marine mammal research programs; and (5)

developing criteria for selecting animals for more

stringent sampling.

Table 5. Effects seen in laboratory rodents and other organisms exposed in utero or perinatally to

organochlorines and other chemicals of concern for marine mammal conservation. 

(Effects may be dose-dependent and, for some contaminants, it is not known to what extent

marine mammals encounter these chemicals in amounts likely to cause the effects listed.)

Chemical Male Offspring Effects Female Offspring Effects

In utero TCDD Epididyal agenesis

Reduced epididymal and ejaculated sperm

Delayed puberty

Small reductions in sex organs

Testis affected at higher dosages

Infertility

Ovarian atrophy

Female tract and ovarian tumors

Malformed external genitalia

Shortened reproductive life span

Lower implantation rate (hamster)

Low survival of pups (hamster - F2)

In utero PCBs - AH R agonist Same

Greater effect on testis - smaller and low sperm

Same

In utero p,p DDE Shortened anogenital distance at birth

Reduced sex accessory gland size

Hypospadias

Retained nipples

None yet detected 

Perinatal xeno-estrogens Slight reduction in epi-sperm and testis size (5%)

Sex organ size

No known malformations

Pseudoprecocious puberty

Shortened reproductive life span with

 loss of estrous cyclicity

Perinatal PCBs Hypothyroidism leading to:

Enlarged testis

Hearing loss

Central nervous system problems

Same central nervous system problems 

 as male

Same reproductive effects as prenatal 

PCBs

(1) Defining endpoints of endocrine disruption that can be examined and tested in marine mam-
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

37

mals. Carefully selected endpoints from the

comprehensive list in Table 6 should be used to

study the effects of EDCs on marine mammals.

Studies should include controlled, longitudinal

experiments using captive or semi-captive marine

mammals, as well as strategic sampling of animals

from wild populations (stranded, bycaught, or taken

in hunts). Some endpoints can only be affected by

in utero exposure, as developmental life stages are

extremely sensitive to EDCs. Other endpoints are

appropriate for both developmental and adult

exposures. Elsewhere (under “Criteria for Selecting

Animals for More Stringent Sampling,” item 5

below), several key species are identified for extensive additional investigations. These species were

selected because we have considerable information

on their reproductive biology and demographics,

and therefore subtle endocrine alterations could be

detected and evaluated. For these species, we

highly recommend that additional endpoints be

used, depending on the hypothesis and study design.

Extensive use of the endpoints listed in Table 6 may

be warranted on a case-by-case basis, dictated by

the nature of the problem.

The endpoints described here include

morphological, histological, biochemical, gravimetri

c, morphometric, endocrine, and behavioral assessments. Those specifically altered by in utero exposure, but that are assessed after birth or during

adulthood, are indicated by an asterisk. Multiple

endpoints measured on a target organ are more

valuable than a single endpoint examined in isolation. This is because a comprehensive evaluation

provides a “weight of evidence,” indicating that an

observed effect is not spurious and is very likely the

result of contaminant exposure. Moreover, as two

endpoints never provide exactly the same information, examination of multiple endpoints strengthens

our understanding of the effects of a specific contaminant on the reproductive system. Note that

several of the endpoints listed in Table 6 need to be

standardized and validated for use with the marine

mammal under investigation. Comprehensive

necropsy of animals and an added emphasis on

collection of fetal contaminant data would help

reduce uncertainty about the effects of EDCs during

the developmental life stages of marine mammals.

(2) Development of new assays. The following

in vitro cellular and molecular assays need to be

developed for selected species of marine mammals:

(1) isolation and cloning of steroid and marine

mammal nuclear receptors and an appropriate

luciferase reporter construct; and (2) identification

of cellular and molecular biomarkers indicative of

exposure to EDCs during development, with emphasis on abnormal gene expression in reproductive

tissues. (Some existing assays used with non-marine

mammals may be suitable, especially for estrogens,

androgens, and thyroid hormones.)

(3) Maternal/fetal pharmacokinetics: recommendations for expanded sampling of target

tissues for contaminants. Most tissue-contaminant

analyses in marine mammals have measured levels

of organochlorines in blubber, and to a much lesser

extent blood and milk. Because chemical exposures

during development are of particular concern, there

is a need to learn more about the toxicokinetics of

the transfer of contaminants between maternal and

fetal tissues. This could be studied experimentally

in selected species, allowing predictions of exposure

in various fetal target tissues during gestation.

Expanded sampling of fetal and neonatal

tissues from bycaught, stranded, or hunted marine

mammals would improve knowledge of gestational

exposure. Of particular value would be paired

sampling of mothers and their offspring (e.g., when

pregnant females are found stranded, or killed in

bycatch or hunts). Additional tissues to collect for

contaminant analysis in adults (in addition to blood,

blubber, and milk) include liver, brain, gonadal,

kidney, and placental tissues. In fetuses and neonates, recommended tissues for contaminant analysis include brain, liver, blood, muscle, blubber, and

gonadal tissues. The contaminant levels from

various target tissues would be very useful to guide

the dose ranges used for mechanistic studies with
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surrogate species (such as laboratory rats) in a

controlled experimental setting.

(4) Opportunities afforded by existing marine

mammal research programs. The infrastructure and

trained personnel exist for necropsy and livecapture-release collections through the Marine

Mammal Health and Stranding Response Program

(MMHSRP). The MMHSRP coordinates a national

stranding program that uses volunteers to monitor

mortality events, collect baseline data from strandings, and collect specimens from stranded animals

for scientific investigations. In addition, the

MMHSRP coordinates a biomonitoring program

that collects specimens for health and contaminant

monitoring or investigations through hunting,

fishery bycatch, unusual mortality events, and mass

strandings. The program also provides training for

specimen collection to support forensic investigations and stranding response. The program has

relied on partnerships with non-government and

other government agencies and on a network of

trained personnel and volunteers who follow wellestablished protocols for specimen collection. This

network provides access to a large number and a

great diversity of samples.

In addition to the MMHSRP, there are archived specimens and ongoing programs at oceanaria and other facilities. These can supplement the

tissues, fluids, and biological data available from the

MMHSRP and thus enhance support for the research needs outlined above. Marine mammal cell

lines have been developed from several species and

from several organs, including kidney, epidermis,

liver, and lymph gland. Further development of cell

lines is underway. 

(5) Criteria for selecting animals for more stringent sampling. The following criteria should be

taken into account in selecting animals for more

stringent sampling: (1) focus on an area where

trained personnel are readily available; (2) examine

animals with a range of health conditions; (3)

examine animals with a range of ages and sexes; (4)

examine animals that occupy a gradient of habitats

(i.e., from relatively pristine to highly polluted); (5)

consider the feasibility of obtaining quality samples,

in terms of both freshness and quantity; and (6)

choose species for which there is adequate information on reproductive physiology.

Based on these criteria, we propose the

following as index or model species: (1) Phocidae,

harbor seal; (2) Otariidae, sea lions (northern and

California); (3) Odontoceti, harbor porpoise, bottlenose dolphin, and beluga whale; (4) Mysticeti,

bowhead whale and minke whale; (5) Sirenia,

Florida manatee. Additional potential exists for

using sea otters, walruses, and polar bears.

References

Addison, R. F. 1989. Organochlorines and marine mammal reproduction. Canadian Journal of Fisheries and

Aquatic Sciences 46:360–368.

Aguilar, A., and A. Borrell. 1994. Assessment of organochlorine pollutants in cetaceans by means of skin and

hypodermic biopsies. Pages 245-267 in M. C. Fossi

and C. Leonzio (eds.), Nondestructive Biomarkers in

Vertebrates. Lewis Publishers, Boca Raton, Florida.

Asper, E. D., D. A. Duffield, N. Dimeo-Ediger, and D.

Shell. 1990. Marine mammals in zoos, aquaria and

marine zoological parks in North America: 1990

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Boon, J. P., P. J. H. Reijnders, J. Dols, P. Wensvoort, and

M. T. J. Hillebrand. 1987. The kinetics of individual

polychlorinated biphenyl congeners in female harbour seals (Phoca vitulina), with evidence for

structure-related metabolism. Aquatic Toxicology

10:307–324.

Colborn, T., and C. Clement (eds.). 1992. Advances in

modern environmental toxicology vol. XXI.

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Princeton Scientific Publishing, Princeton, N.J.

DeLong, R. L., W. G. Gilmartin, and J. G. Simpson.

1973. Premature births in California sea lions:

association with high organochlorine pollutant

residue levels. Science 181:1168–1170. 

Gilmartin, W. G., R. L. DeLong, A.W. Smith, J. C.

Sweeney, B.W. De Lappe, R.W. Risebrough, L. A.

Griner, M. D. Dailey, and D. B. Peakall. 1976.

Premature parturition in the California sea lion.

Journal of Wildlife Diseases 12:104–115.

Gray, L. E. 1992. Chemical-induced alterations of sexual

differentiation: a review of effects in humans and

rodents. Pages 203-230 in T. Colborn and C. Clem-
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ent (eds.), Advances in Modern Environmental

Toxicology, Vol. XXI. Chemically-induced alterations in sexual and functional development: The

wildlife/human connection. Princeton Scientific

Publishing, Princeton, N.J.

Gray, L. E., J. Ostby, C. Wolf, C. Lambright, and W. R.

Kelce. 1998. The value of mechanistic studies in

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effects in wildlife. Environmental Toxicology and

Chemistry 17:109–118.

Pitcher, K. W., and D. G. Calkins. 1981. Reproductive

biology of Steller sea lions in the Gulf of Alaska.

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Reddy, M., S. Echols, B. Finklea, D. Busbee, J. Reif, and

S. Ridgway. 1998a. PCBs and chlorinated pesticides

in clinically healthy Tursiops truncatus: relationships

between levels in blubber and blood. Marine Pollution Bulletin 36:892–903.

Reddy, M. L., J. S. Reif, S. Echols, and S. H. Ridgway.

1998b. Relationship between blubber organochlorine

concentration and pregnancy outcome in Tursiops

truncatus. (Abstract.) Page 110 in Proceedings of the

International Association of Aquatic Animal Medicine, 3–6 May 1998, San Diego, CA.

Reddy, M. L., and S. Ridgway. 1995. Values of some

organochlorines in the blubber, blood, milk and

calves of live Tursiops truncatus. (Abstract.) Page

96 in Eleventh Biennial Conference on the Biology

of Marine Mammals, 14–18 December, Orlando, FL.

Reijnders, P. J. H. 1980. Organochlorine and heavy

metal residues in harbour seals from the Wadden Sea

and their possible effects on reproduction.

Netherlands Journal of Sea Research 14:30–65.

Reijnders, P. J. H. 1986. Reproductive failure in common seals feeding on fish from polluted coastal

waters. Nature 324:456–457.

Reijnders, P. J. H. 1990. Progesterone and oestradiol-17B

concentration profiles throughout the reproductive

cycle in harbour seals (Phoca vitulina). Journal of

Reproductive Fertility 90:403–409.

Reijnders, P. J. H. In press. Reproductive and developmental effects of endocrine disrupting chemicals on

marine mammals. In J. G. Vos, G. D. Bossart, and

M. Fournier (eds), Toxicology of Marine Mammals.

Taylor & Francis, Philadelphia, PA.

Ridgway, S., and M. Reddy. 1995. Residue levels of

several organochlorines in Tursiops truncatus milk

collected at varied stages of lactation. Marine

Pollution Bulletin 30:609–614.

Schardein, J. L. 1993. Hormones and hormonal antagonists. Pages 271–339 in Chemically Induced Birth

Defects. Marcel Dekker, New York.

St. Aubin, D. J., S. H. Ridgway, R. S. Wells, and H.

Rhinehart. 1996. Dolphin thyroid and adrenal hormones: circulating levels in wild and

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12:1–13.
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Working Group on Risk Assessment

Working Group Members: Aguirre, Castellini,

Colborn, DeMaster (Leader), Grose, Hansen, Harwood, Jones, Matta, Reif, Ross, Schwacke, Stein,

Wells (Rapporteur)

Introduction and Overview

Marine mammals are exposed to a complex array of

environmental contaminants, many of which are

persistent, fat-soluble, and accumulate through the

food web. Understanding the risks that these

chemicals pose to marine mammals is not easy. It

requires a systematic approach involving extrapolation from model species and laboratory experiments.

Risk assessment is considered here in the context of

the formal evaluation process established by the

U.S. Environmental Protection Agency (EPA). In

the EPA’s Ecological Risk Assessment Framework,

the risk assessment is a necessary step preceding

risk management. A key component of the framework is an iterative approach between risk assessment and risk management, which ensures discussion between the risk assessors and risk managers as

information is developed (Figure 1). This process

begins with problem formulation: contaminant

sources, fates, and pathways are described; contaminants of concern and their modes of action are

discussed; and receptors of concern are identified.

One outcome of problem formulation is a conceptual model that, in this instance, describes the ways

in which marine mammals or their tissues might be

exposed to and affected by contaminants. A second

outcome is identification and assessment of endpoints that are explicit expressions of attributes that

should be evaluated and protected. Typically, a risk

assessment describes specific hypotheses to be

tested and measurements that can be made in the

analysis phase to evaluate the assessment endpoints

of concern. 

Exposure assessments are conducted to evaluate contact with particular contaminants of concern.

Contact often comes about through ingestion, and

exposure is evaluated through measurements of

body burden. Information for exposure assessment

can be derived from available databases or through

directed sampling. Databases for descriptions of

exposure are expanding internationally. The EPA

and the National Toxicology Program have created

a vast database on chemical production and use.

They are in the process of setting priorities for

testing and screening for endocrine disruption the

tens of thousands of chemicals presently used in the

United States. Production volume, use, persistence,

and environmental and human exposure are being

considered, along with toxicological information

that is already available about a small fraction of

chemicals in use. In related efforts, the EPA is

collaborating with the Organization for Economic

Cooperation and Development (OECD) and the

Japanese Environment Agency to develop common

methodologies and to apportion screening and

testing responsibilities.

Effects assessments can involve direct measurements of effects on the animals of interest or the

modeling of effects using measurements obtained

from surrogate species. As indicated in Figure 2,

the interplay of controlled laboratory or captive

studies and field correlative studies can be crucial to

providing the requisite information on effects.

Laboratory studies might include in vitro experiments, or exposure trials using single chemicals or

complex mixtures in laboratory animals. The

selection of a surrogate model or set of models for

marine mammals will depend on the nature of the

question being posed (e.g., whether it relates to

reproduction, immunotoxicology, pharmacology, or

the potential for endocrine system disruption).

Researchers should consider in advance how strong

the inferences about a marine mammal species will

be when based on comparisons (extrapolations)

from observed processes or effects in the model

species. Laboratory rodents have been used extensively in studies of human toxicology and pharmacology. Work with surrogate models can generate

mechanistic information that is badly needed re-
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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(Figure 1)
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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(Figure 2)
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

45

garding toxicity, and can complement controlled

studies of captive marine mammals or more ecologically relevant field studies of marine mammals. 

Risk characterization uses the information from

exposure and effects assessment to evaluate the risk,

generally using a “weight of evidence” approach.

This approach balances the information on effects,

obtained mainly or entirely from the mechanistic

understanding provided by laboratory studies (often

associated with high levels of confidence), against

the results of captive-animal or field studies which

have greater ecological relevance but are often

associated with lower levels of confidence (Fig. 3).

Uncertainty in all assessment components should be

clearly discussed so that the uncertainty in conclusions about risk is understood. The ecological

significance of the risk should also be discussed,

including how effects on individuals have been

extrapolated to effects on populations and how risks

from contamination have been compared to risks

from other stressors. The ideal outcome of risk

characterization is identification of threshold concentrations, above which risk becomes significant

and risk management is required.

The working group examined the risk assessment approach relative to marine mammals and

persistent ocean contaminants. The following four

elements of this approach were evaluated by separate subgroups: (1) risk characterization; (2) important factors that determine exposure; (3) measuring

adverse effects in marine mammals; and (4) surrogate approaches to assessing the effects of contaminants on marine mammals. A fifth subgroup examined a case study and performed the initial stages of

a risk assessment on the California sea lion. (The

purpose of the latter exercise was to use the risk

assessment framework to explore a case example

with a fair amount of background information

readily available, not necessarily because of any

current critical population problems.) The results of

these efforts are presented on the following pages.

Below is a list of overall recommendations from the

full working group.

Overall Recommendations

(1) Integration of Field and Laboratory Studies.

Field studies and controlled-exposure experiments

are valuable tools for determining cause-and-effect

relationships between environmental contaminants

and adverse effects. In the case of marine mammals, both approaches have limitations, and it is

unreasonable to expect that one approach alone will

be sufficient to determine whether cause-and-effect

links exist. Progress in this area will be made most

rapidly and cost effectively by integrating the two

approaches.

The major difficulties of conducting field

studies and controlled-exposure experiments with

marine mammals are (1) marine mammals are

exposed in the wild to complex contaminant mixtures, (2) controlled-exposure studies with marine

mammals in captivity are logistically difficult,

prohibitively expensive, and have ethical aspects

that must be carefully considered, and (3) by themselves, only very extensive field or laboratory

studies could prove a cause-and-effect relationship.

We recommend an integrated approach, as

outlined in Figure 4. A similar approach has proven

successful in studies of the effects of contaminants

on wildlife in the Great Lakes region (Giesy et al.

1994). Extensive field studies are conducted to

provide evidence of adverse effects in the species of

concern. These studies must involve some analytical work to provide correlative evidence of the

involvement of specific chemicals or chemical

classes. Extracts containing the chemicals of

concern are used to expose a bank of likely surrogate species. The surrogate species chosen will

include easily manipulated laboratory species,

phylogenetically allied species, or even in vitro cell

cultures. The key to selecting appropriate surrogate

species will be the observation of the same or

homologous effects as observed in the wild population. The effects of interest could range from

biochemical responses to complex biological responses such as immunotoxicity.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

46

Figure 3. Extrapolation in risk assessment: the “weight of evidence.” (Adapted from Ross 1999)

Once a suitable surrogate model species has

been chosen, the following procedures can be used

to identify the chemical agents responsible for the

(observed effect. The causative chemical agents are

identified by a series of fractionation procedures

which are monitored using the surrogate model

species. Successive fractionation procedures provide a mixture containing fewer and fewer chemicals, which is eventually amenable to analytical

characterization of all components. At the end of

this process, the agents which caused the adverse

effect in the surrogate species have been identified.

To confirm the cause-and-effect relationship, the

chemical agent or mixture can be reconstituted from

pure chemicals. This agent or mixture should then

cause the same adverse effect in the surrogate

species. If required, the same reconstituted mixture

can be applied to the initial target species of concern

to confirm the cause-and-effect relationship inferred

from the original field studies.

Advantages of this approach include abilities to

(1) handle complex mixtures and identify causative

agents; (2) select the most appropriate surrogate

model species for the field species and endpoint of

concern; (3) make a “weight of evidence” decision

at various stages; (4) eliminate the final targetspecies testing if adequate weight of evidence is

provided; and (5) cope with various chemical

classes based on the methods and tissues used to

prepare the crude extract.

(Figure 4)
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

47

(2) Standardization of Protocols for Sampling

and Analyses. To insure comparability of data

from a variety of studies, a basic set of standardized

protocols should be developed for sampling and

analyses. These protocols should be applied to

targeted sampling projects, and they should be

expanded with the goal of achieving international

acceptance and application. It is recommended that

an explicit list of samples be developed to allow

optimal comparability across studies, but this list

should be limited to those protocols which are

feasible under field conditions, and are not unduly

burdensome. Reporting procedures should be

standardized and refer to total body burdens of

chemicals (taking into account variable blubber

thickness) rather than simply chemical concentrations. Reports should present data from individual

animals, not summary statistics alone.

(3) Development of Biomarkers to Aid in Validation of Risk Assessment. The current suite of

biomarkers for contaminant exposure must be

systematically examined and applied whenever

useful to marine mammals. However, we urge

research into the development of sensitive, rapid,

inexpensive, and field-adaptable biomarkers. Many

procedures currently necessary for biomarker or

contaminant samples are difficult to conduct in field

conditions. Furthermore, the assay costs can be

restrictive. The net result is that the correct samples

may not be taken and when they are, may never be

analyzed. If biomarkers were available for tissue or

blood samples that could be easily obtained, stored,

transported, and assayed, this would significantly

increase our ability to assess contaminant impacts in

the field.

(4) Study Designs That Allow for Increased

Confidence and Reduced Uncertainties. Study

designs should take into consideration the required

statistical power, should present clear hypotheses,

should take into account life history and environmental variables (e.g., age, sex, season, etc.) and

should include controls whenever possible.

(5) Use of a “Weight of Evidence” Approach in

Reaching Decisions for Risk Management. Risk

characterization incorporates data from

well-designed field studies, laboratory analyses,

surrogate animal models, in vitro experiments,

biomarker studies, and other sources. The weight of

evidence should be considered in reaching riskmanagement decisions. In the absence of conclusive

data, a precautionary approach is recommended.

(6) Additional Information on Dose-Response

Relationships. We endorse the EPA risk assessment approach. Based on it, we encourage the

design and implementation of studies that quantify

relationships between contaminants and marine

mammals, either directly or through laboratory

studies of models or surrogates. There is a need to

identify critical uncertainties, leading to specific

research programs for characterizing the risk posed

by persistent ocean pollutants.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

48

Risk Characterization Subgroup Report

Subgroup Members: Aguirre, DeMaster, Harwood

(Co-Rapporteur), Matta (Co-Rapporteur), Reif 

Issue Title: Risk Characterization

Issue Description and Rationale:

Risk characterization considers estimates of exposure along with information about responses to

contaminants to provide an indication of the expected effect(s) of the contaminants on an individual

or a population. This risk-evaluation process is a

fundamental component of the EPA ecological riskassessment framework. To the best of our knowledge, it has not been applied to any marine mammal

population. 

Although this report is specifically concerned

with identifying the types of information required

for risk characterization, it also discusses actions

required to resolve some of the issues that can

complicate the application of a risk-assessment

approach to ecological problems. These include the

role of episodic or catastrophic events, the effects of

other environmental stressors, and issues of morbidity and chronic effects as they affect estimation of

the risk from toxic chemicals.

Means to Resolve the Critical Uncertainties

Surrounding the Issue

Risk Integration for Endangered and Depleted

Species. The probability that an individual will be

affected by a particular contaminant can be estimated from a knowledge of the exposure to which

each individual is subjected and the response associated with each level of exposure. In other words,

we need to know the statistical distribution of

exposures and the precise form of the dose-response

curve. The ways by which this information can be

obtained are described elsewhere in this working

group’s report. 

For populations of endangered species, the

death of even a single individual can influence the

survival prospects of the population. Therefore, it

is sufficient to estimate a feasible range for the

number of individuals which may be affected by the

contaminant in question, and to decide whether this

potential loss is acceptable. As part of the process,

it must be recognized that the dynamics of small

populations have unique features which are a direct

consequence of their small size. These features are

a result of the population’s susceptibility to stochastic effects, inbreeding depression, etc. Population

viability analysis is an approach specifically designed to incorporate these factors into an evaluation of a population’s potential to persist over a

given period of time.

Parameterizing the effects of contaminants in

models of depleted populations requires information

on the induced changes in the age-specific rates of

survival and reproduction. Recently developed

mark-recapture techniques, using longitudinal data

sets, are remarkably good at producing acceptably

precise estimates of survival. These techniques can

be modified to incorporate information on co-variates to allow for the evaluation of survival, conditional on a specific value for a given co-variate.

Contaminant levels can be such co-variates. A

similar approach could be used to estimate the

impacts of contaminants on reproduction. The key

to such analyses is the availability of long-term data

on marked or individually identifiable animals.

Unfortunately, efforts to parameterize the

effects of contaminants in population models for

marine mammals based solely on current trends in

abundance are likely to be unsuccessful. This is

because of the relatively long times needed to

estimate current trends in abundance for marine

mammal populations. Further, given the almost

complete absence of quantifiable information on the

mechanisms that regulate the growth of marine

mammal populations, attempts to attribute changes

in the population growth rate to contaminant effects

are likely to be confounded by density-dependent

responses. Because of these difficulties, it will

usually be impossible to accurately predict the level

of effect due to a contaminant that would cause a

specified change in the size of a marine mammal

population over a particular time interval.

The Role of Episodic or Catastrophic Events. It
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

49

is often suggested that the negative effects of contaminant exposure are likely to be most obvious

when a population is under stress during episodic or

catastrophic events such as epizootics, blooms of

toxic algae, or El Niño events. Such events can

provide particularly good opportunities for detecting

the role of contaminants. A comparison between

the distribution of contaminant burdens in animals

which die during the event and the distribution

before the event can provide some information on

the form of the dose-response curve. Thus, it is

important to have good baseline information on

populations believed to be at risk from such events,

and to have in place a protocol and logistic support

for adequate sample collection during the event.

Although the impact of such events on a population

may appear severe, the long-term impact depends

on the interval between them.

Other Environmental Stressors. Even if a risk

assessment indicates that a population of marine

mammals is likely to be negatively affected by

exposure to contaminants, the effect may be relatively small in comparison to the effects of other

stressors (e.g., environmental change, disturbance,

or fishery interactions). Indeed, changes over time

in these other stressors may make it particularly

difficult to detect the effects of contaminants against

a background of high variability in survival and

fecundity. It is therefore important to document the

effects of these stressors on survival and fecundity.

Networks, such as the Marine Mammal Health and

Stranding Response Program, that attempt to determine the cause(s) of death of animals found dead,

are an important component of this process.

Chronic and Sub-Lethal Effects. Chronic and

sub-lethal effects attributed to contaminants will not

normally have an immediate effect on the dynamics

of an affected population. However, they can

provide an important indication that more acute

effects may occur at higher levels of exposure.

Provided that there is agreement on what constitutes

an unacceptable level of occurrence for such effects,

and that there is enough information to derive a

dose-response relationship, these effects can be used

as endpoints for risk assessment.

Suggestions Regarding Existing Monitoring

and Research Programs

Programs that integrate laboratory and field studies

in order to determine exposure and response to

contaminants, as recommended elsewhere in this

report, need to be implemented before risk assessment can be carried out in a substantive way on

most marine mammal populations. Programs to

monitor survival and fecundity rates, as well as

population size, for populations which may be

affected by contaminants need to be established as

soon as possible.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

50

Exposure Subgroup Report

Subgroup Members: Grose, Harwood (Rapporteur),

Jones, Stein

Issue Title: Important Factors That Determine Exposure

Issue Description and Rationale:

Characterizing exposure is fundamental to any risk

assessment. However, available data on the concentrations of contaminants in specific marine mammal

tissues cannot be used to estimate exposure directly.

The challenge in measuring the exposure of marine

mammals to specific contaminants is that most

approaches used in conventional risk assessment are

inapplicable. 

The main routes of exposure for marine mammals are directly through food, by transmission

from mothers to their offspring in gestation and

lactation, by absorption through the skin, and by

inhalation. Exposure can also be indirect in the

sense that contaminants bioaccumulate in certain

tissues (such as blubber), and are subsequently remobilized in response to metabolic demand. The

most important route of exposure varies among

contaminants and species. The timing of exposure,

in terms of both the annual cycle and the species’

life history, may be critically important in determining effect. All of these factors influence the degree

to which individuals are exposed to contaminants on

a daily basis.

Organic contaminants which are resistant to

metabolism and are hydrophobic (such as dioxins,

the organochlorine pesticides, and PCBs) will

continue to bioaccumulate in the tissues of marine

mammals. They are therefore a continuing cause

for concern. PAHs and many industrially produced

chemicals (e.g., insecticides, herbicides, fungicides,

fire retardants, plasticizers, low molecular-weight

polymers, and other unidentified high-volume

compounds) are now ubiquitous in the marine

environment. Some of them are metabolized by

many organisms, especially vertebrates. There is

less potential for bioaccumulation of these compounds. However, some of them or their metabolites are highly toxic, and their ingestion or inhalation by marine mammals would be a cause for

concern. For such compounds, it may be very

appropriate to measure biological markers of exposure. There is considerable uncertainty about the

occurrence, pathways, and fate of many of these

contaminants in the marine environment. This

means that there is also uncertainty about the ways

in which marine mammals may be exposed to them.

Marine mammals may be exposed to metals in

both their inorganic and organic forms. By no

means all of the exposure to these compounds is of

anthropogenic origin. This is particularly true for

cadmium, selenium, and mercury. In general, the

organic forms of metals are more toxic, have higher

potential to be more bio-available, and tend to

accumulate more than the inorganic forms. The

pathways by which these compounds reach marine

mammals, and their toxicity, depend to a great

extent on speciation and transformation within the

animal.

Marine mammals are exposed to complex

mixtures of all of the above contaminants. The

combined effect can be assessed if the constituents

of a mixture have the same mode of action at the

physiological or biochemical level (e.g., estrogenici

ty, or dioxin-like Ah receptor binding). Where this

is the case, it should be possible to apply the toxic

equivalency factor (TEF) approach developed for

assessing the potential effects of dioxin-like compounds. The combined effect can then by estimated

by summing the toxic contribution for each contaminant. However, if compounds in a mixture have

more than one mode of action, then the potential for

synergism or antagonism must be considered.

The ways in which contaminants are distributed

in the marine environment depend on how they

enter the system (e.g., from a point source or atmospherically), and on how they are transported

through the system and deposited by physical and

biological processes. Temporal and spatial overlap

between contaminant distribution and the distribution of each marine mammal species governs the

extent of exposure. Thus, better information on
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

51

sources and paths of distribution is essential if past

and future levels of exposure are to be assessed.

Another factor that introduces uncertainty into risk

assessments is the variability in sample collection,

analytical techniques, and the ways in which data

are presented and summarized.

Means to Resolve the Critical Uncertainties

Surrounding the Issue

(1) Use Models Derived from Other Species.

The mechanisms by which metals and

non-accumulating organic compounds are taken up

and distributed by marine mammals are expected to

follow the same principles as observed in other

mammals. Thus, models derived from other species

should be directly applicable to marine mammals,

although validation of this assumption will be

necessary in at least some contexts.

A unique physiological characteristic of marine

mammals is the presence of a large blubber layer.

The dynamics of lipids in marine mammals markedly affect the distribution of hydrophobic organic

contaminants. However, lipid dynamics have little

influence on the distribution of inorganic forms of

metals. The distribution of metals is primarily

determined by mechanisms that operate in organs

such as the liver and kidney. Therefore, disposition

and biotransformation of metals in other mammalian

species should be directly applicable to marine

mammals. Species-specific differences may exist,

however, so that comparative physiological and

toxicological studies may be necessary to assure the

extent of direct application to marine mammals.

(2) Estimate Population Exposure. Average

population exposure to accumulating organic

compounds can be estimated from the distribution

of total burden of each contaminant per animal in

specific age and sex categories.

An expression for the expected total burden of

a particular contaminant in the depot tissues, such as

blubber, of an individual can be derived. It involves

the average exposure to that contaminant, the

statistical distribution of the contaminant in prey,

and the rate at which the contaminant is metabolized

or excreted. This expression can be used to describe

the expected distribution of contaminant burdens in

a particular section of the population (e.g., all

sub-adults, all adult males, all mature females). The

expected distribution can then be fitted to observed

distributions in order to estimate the average exposure for the population. Unfortunately, most published reports only document the concentration of

contaminants in blubber (often on a lipid weight

basis). An estimate of the total quantity of blubber

carried by the animal is required if total body

burden is to be estimated. This additional information is available for some populations (e.g., harbor

seals and gray seals in the North Sea). Although

muscle tissue is typically much lower in lipids than

blubber, it constitutes a major proportion of body

mass, and therefore in some instances contaminant

burdens in the lipid fraction of muscle may be

necessary to enter into estimations of total body

burdens.

(3) Increase Knowledge about Lipid Dynamics

and Blubber Physiology. Physiological condition

affects the distribution of accumulating organic

compounds within an animal’s body. Further

research on lipid dynamics is required if the processes determining this distribution are to be understood (i.e., how do lipid dynamics and physiological

demands affect circulating levels of lipid and contaminants?). The lipid stores in a marine mammal’s

blubber represent a reservoir for the storage of

lipophilic contaminants. Depletion of this lipid

reservoir due to fasting, starvation, or lactation can

lead to release of contaminants into the blood

stream and delivery of these contaminants to sites of

action. As with the metal contaminants mentioned

above, it is assumed that adverse contaminant

effects at sites of action can be predicted from

contaminant concentrations in the blood. Therefore,

studies which relate adverse effects to blood contaminant concentrations in other mammal species

will, in general, be predictive of adverse effects in

marine mammals. Exceptions may arise when there

are class- or species-specific differences in particular cellular receptors (e.g., Ah-receptor), resulting in

variations in species sensitivity to individual contaminants. In these situations, in vitro studies can
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

52

help determine the extent of variation between

species.

The dynamic between accumulation from food

sources and storage, and release from blubber

reserves represents a buffering system for contaminant concentrations in the blood. As such, it is a

critical factor affecting circulating levels of contaminants. Information already available on contaminant levels in blubber would have greater value if

we had a better understanding of how blubber

dynamics affect blood levels of bioaccumulative

organic contaminants. The relationship between

blubber and blood contaminant concentrations is not

adequately understood. Information about this

relationship is best obtained by parallel analysis of

blubber and blood samples from animals whose

“condition” is assessed by measuring blubber

thickness and lipid content. Suitable subjects for

such studies would include animals sampled in

catch-and-release programs, animals taken as

bycatch in fisheries, animals being rehabilitated

after stranding, and animals held captive under

controlled experimentation.

(4) Determine Mechanisms of Action and Target Sites. Interactions of contaminants at target

sites will determine their biologically effective dose.

The nature of these interactions is unlikely to be

unique to marine mammals. Therefore, information

from studies of other mammals (including humans)

should be directly applicable. 

For complex mixtures of chemicals operating

through the same mode of action, an additive TEF

mechanism has been extensively validated. As the

same mechanisms are expected to operate in marine

mammals, this approach can be used for these

chemical mixtures. Some validation of TEF values

using in vitro techniques will be required. The

possibility exists of interactions between toxic

processes (e.g., similar to drug interactions). The

nature and consequences of these interactions need

to be assessed with model species in laboratory tests

before their impacts on marine mammals can be

considered.

The measurement of concentrations of a

contaminant in tissues will not always provide

sufficient information to assess the dose that would

be toxicologically significant, referred to as the

biologically effective dose. For example, some

metabolites (e.g., DDT methylsulphones, hydroxyPCBs) of bioaccumulative compounds are considered toxic. Moreover, for non-bioaccumulating

contaminants, measurement of the interaction of the

contaminant or its metabolite with a target site or

receptor (e.g., DNA, acetylcholinesterase) is necessary to determine the toxicologically relevant dose.

In marine mammals, nondestructive sampling

is often the preferred approach for collecting exposure data, particularly in free-ranging animals.

However, samples that can be collected

non-destructively are often not from the target site

for many of the contaminants of concern. This

situation is not unique to marine mammals. Studies

with humans have the same considerations, and the

literature on relevant studies should be directly

applicable. The primary issue of concern is the

validation of a measurement in a tissue, such as

blood, as a reliable surrogate for a target site in an

internal organ. Validation studies in marine mammals are likely necessary to increase the value of

non-destructive samples as surrogates for target

sites/organs in marine mammals.

(5) Augment Sampling with Information from

Multiple Sources of Animals. The most useful

information on exposure is likely to come from

free-ranging or rehabilitated animals. This will

include samples from by-caught and hunted animals. Samples from stranded animals will be most

useful for investigating exposure associated with

episodic events or for augmenting studies based

primarily on free-ranging animals.

Detailed information on circulating levels of

contaminants is required if exposure is to be determined reliably. Such information is best obtained

from free-ranging animals using biopsy sampling or

similar techniques. However, there are limits to the

type and quantity of material that can be collected in

this way, and results from this kind of sampling

program need to be augmented with samples from

animals which are still alive or have only recently

died. The best sources of such samples are rehabili-
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

53

tated, by-caught, and hunted animals. Samples from

stranded animals can be informative, particularly

when episodic events result in large-scale mortality.

However, it should be recognized that the origin of

stranded animals is often difficult to determine, and

that tissue samples from such animals can be in poor

condition.

(6) Develop an Internationally Accepted Protocol for Sampling and Analysis in Relation to

Exposure. This should ensure standardization of

basic data collection and, wherever possible, the

collection of a full set of complementary information on age, sex, “condition,” body composition,

stomach contents, and environmental conditions. A

number of models for this protocol already exist

(e.g., HARMS, IWC recommendations). It is

desirable that this protocol be organized in a hierarchical fashion, with samples assigned to high,

medium, and low priorities. In addition, the protocol should contain a Quality Assurance (QA)/Quality Control (QC) component to ensure comparability

of analytical results. This component should include analysis of blind control samples, exchange of

samples between participating laboratories, and,

where possible, banking of samples for future

analysis. It would be desirable to provide access to

the data sets produced through the application of

this protocol, either directly or in spreadsheet

format, over the Internet.

(7) Develop Information on Dietary Uptake of

Contaminants. While information on diet and

feeding distribution is not essential for determining

current exposure for coastal species, it may provide

the only basis for estimating exposure for pelagic

species. In addition, such information is essential

for a full risk assessment and for understanding the

implications of episodic events. In principle, the

uptake of contaminants by a population can be

estimated from data on (1) diet and feeding distribution; (2) the contaminant burden of each prey

species (and the way this varies in time and space);

and (3) the efficiency with which the contaminants

are absorbed by the species. However, sufficiently

detailed information on diet and prey is rarely, if

ever, available for marine mammals. Historically,

coastal species have been well-studied compared to

pelagic species, which are far less accessible.

Determining exposure levels for pelagic populations

will require extrapolation from similar coastal

species, and modeling uptake from food sources. A

better understanding of the movements and feeding

patterns of pelagic species is also required.

Suggestions Regarding Existing Monitoring

and Research Programs

Future sampling and monitoring efforts in major

national and international programs should give

higher priority to obtaining samples from

free-ranging animals, particularly those whose age

and reproductive history are known; rehabilitated

animals; animals killed incidentally in fisheries

(bycatch); and animals taken in directed hunting

where this occurs. In addition, there is a need to

collect information on body condition and stomach

contents (both prey composition and levels of

contaminants present) whenever possible. Increased

coordination among existing projects should be

encouraged, and historical data on contaminant

levels in individual animals need to be made more

widely available.

The Marine Mammal Health and Stranding

Response Program of the National Marine Fisheries

Service (NMFS) provides the infrastructure in the

United States to determine exposure parameters in

marine mammals. This program should be encouraged to incorporate studies or projects to measure

contaminant burdens (total body burdens) in prey of

marine mammals. The coordination of such studies

or projects with potentially complementary ones

conducted through the NMFS Office of Habitat

Conservation, NMFS Science Centers, or relevant

Department of the Interior agencies would enhance

the efficiency of collecting data on prey species.

Programs intended to monitor contaminant levels in

marine mammals and their prey should incorporate

assessments of trophic structure. Among the methods that could be used are those involving stable

isotopes and fatty-acid profiles.

The Marine Mammal Health and Stranding

Response Program has made substantial progress in

developing QA protocols in the United States.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

54

Efforts at international coordination in QA for

sample collection, analytical methods, and data

archiving are strongly encouraged. Such coordination would facilitate comparisons of data from a

wider range of geographic areas and thus from

animals with differing types and amounts of contaminants. These comparisons would, in turn,

improve our ability to assess relationships between

doses of exposure and observed biological effects

and anomalies.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

55

Measurement of Adverse Effects Subgroup Report

Subgroup Members: Castellini, Hansen, Wells

(Rapporteur) 

Issue Title: Measuring Adverse Effects in

Marine Mammals

Issue Description and Rationale:

Risk assessment for marine mammals relative to

contaminants will require integrated programs

involving field and captive studies with marine

mammals as well as laboratory studies using surrogate or model species. Controlled studies and

experiments are needed to strengthen the correlative

data that are already available. The following topics

are of critical concern and therefore need to be

addressed as quickly as possible.

Identification of Biological Responses. An organism responds to any external stressor or event in one

of three ways: by adapting to exposure and compensating in some way; by removing itself from the

area of exposure and thus eliminating the stress; or,

ultimately, by experiencing the negative effects of

the exposure. Multiple levels of response are

possible, involving behavioral changes, physiological reactions, alterations in reproductive processes,

and impacts on individual and population health.

When applying contaminant models to individual

animals, it is critical to establish levels of threshold

response, response curves, reactions that are appropriate to the insult but not damaging, and responses

that indicate damage to the animal. For example,

the production of metallothionein (MT) is the

appropriate response to increased metal exposure.

The MT is used by the animal’s system to chelate

out the circulating metal and sequester the

metal-protein complex in organs such as the liver or

kidney. Thus, the presence of MT is an excellent

biomarker for exposure to metals, but it also indicates that the animal’s body has reacted appropriately to protect itself from high circulating metal

levels.

Definition of Quantitative Relationships Between

Contaminants and Biological Responses. To

characterize exposure and biological responses to

contaminants for any species, well-controlled

experimental studies are a powerful tool. In the

laboratory, the test species is exposed to varying

doses of the chemical(s) in question. The animal’s

responses can be quantified, but they will depend on

controlled variables, such as sex, age, stage of

development, physical condition, the type and

mixture of the chemical, environmental conditions,

etc. In the field, test animals can be selected based

on estimated or known exposure to the chemical(s)

in question. While field studies are not as easily or

thoroughly controlled as laboratory studies, they

provide the advantage of involving animal subjects

that are faced with a natural suite of stressors. A

combination of laboratory and field techniques is

used routinely in contaminant-wildlife studies, but

has not been widely applied to marine mammals. It

can be useful for establishing mechanistic links

between contaminant chemistry and biological

response.

As noted above with metallothioneins, biomarkers are useful for demonstrating that exposure

to some sort of insult has caused a physiological

response in the animal. Thus, biomarkers can be

useful tools for addressing contaminant problems,

provided, however, that the pathways between the

exposure and the biochemical or physiological

response being measured are well known. Understanding the mechanisms of biomarker production

is critical, but it must be possible to make at least

three key distinctions, as follows: (1) the difference

between markers that demonstrate exposure and

those that show or predict effect. That is, some

markers may simply indicate that a species has been

exposed to a chemical; others may predict responses

not yet expressed by the organism or its offspring;

and, finally, some may be the by-product of damage

induced by the chemical; (2) the difference between

persistent and ephemeral contaminants. Some

chemicals may be extremely dangerous but very

short-lived. If biomarkers could be developed for

these chemicals, then their past presence could be

verified even if the chemicals themselves have

disappeared; and (3) the difference between single-
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

56

and multiple-chemical stressors. That is, any

particular chemical may induce a particular biomarker event, but a mixture of chemicals may

induce a distinctly different marker. Again, these

would need to be investigated by means of carefully

developed experimental studies or by extrapolation

from other species and model systems. 

Work with Marine Mammal Species That Are

Difficult to Study. It is clear that certain marine

mammal species that are at risk from contaminant

exposure will never be adaptable to dose-response

or controlled studies. For example, few offshore or

large cetaceans can be studied with this type of

approach. We urge a conservative risk-aversemanagement approach with these species. Under

ideal circumstances, the goal is to study the species

of interest directly. Since this will not be possible

for many groups, model or surrogate species will

need to become the focal points for contaminant

studies.

Need for Adequate Statistical Power to Detect

Effects. Regardless of whether a contaminant

project is to be conducted in the laboratory or the

field, it is essential that a statistical model be developed to determine the appropriate number of animals before the experimental protocol begins. It is

of no benefit to study a sample that is too small for

valid statistical results. Nor is there any benefit in

sampling more animals than is necessary. In the

laboratory, standard statistical methods of determining significance and power can be applied. In the

field, it might prove necessary to adapt the mathematical models of epidemiology to understand the

impacts of contaminants on whole groups of animals. This would involve stratification by age, sex,

reproductive condition, season, location, etc.

An additional consideration is that the impacts of

contaminants may be trans-generational. If this is

known or suspected to be the case, the sampling

scheme may require extended periods of time to

allow for the long reproductive lives of individuals.

Consideration should be given to conducting longitudinal studies of identified family lines.

Means to Resolve the Critical Uncertainties

Surrounding the Issue

The “weight of evidence” concept has been useful

in establishing the seriousness of concerns about

contaminant risks in marine mammals. Controlled

studies and experiments can be used to strengthen

correlation data. Four broad types of study are

identified and discussed below.

(1) Use of Captive and Free-Ranging Animals in

Controlled Studies. The study of both captive and

free-ranging animals is essential for quantifying

contaminant effects in marine mammals. Non-lethal

experiments on captive marine mammals allow for

tightly controlled conditions; detailed longitudinal

analyses; the use of animals that have been or are

being rehabilitated; and, usually, ready access to

sophisticated medical or research facilities. Diet,

contaminant level, activity pattern, and a host of

other variables can be controlled (including stress),

making it possible to quantify effects accurately. In

some cases, field studies can be longitudinal projects and allow for a compare-and-contrast scheme

in which animals from highly contaminated areas

are compared to animals from areas with low contaminant levels; individuals of different age, reproductive, or sex classes are compared; or the contaminant burdens of individuals can be tracked through

time.

(2) Selection of Marine Mammal Model Species.

As noted in the “Issue Description and Rationale”

section above, it will probably never be possible to

study many species of marine mammals in sufficient

detail to make informed risk assessments on their

behalf. Therefore, we need to identify species that

can be studied, both for their own benefit and as

models for less easily studied species. For example,

historically, the most closely studied species have

been those that are relatively easy to approach and

that live near shore or haul out in accessible areas.

Because of their proximity to human activities,

these species also happen to be among those most at

risk from contaminants. Thus, they need to be

studied for their own sake and as models of animals

exposed to high contaminant loads. The 1995

Bergen workshop of the International Whaling

Commission recommended as model cetacean
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

57

species the bottlenose dolphin, beluga whale, harbor

porpoise, and Amazon river dolphin. In addition to

these, the identification of a model baleen whale

species would be helpful in focusing field studies

for this cetacean group. For pinnipeds, we recommend the harbor seal, California sea lion, elephant

seals, fur seals, Weddell seal, and gray seal. These

species, and others with large databases associated

with them, can be studied in both captive and field

conditions, sometimes close to human population

centers. These species will allow detailed laboratory studies, field studies, and studies of individuals.

Thus, they can be used to test hypotheses at both the

individual and the population level.

(3) Development of Models of Lipid and Blubber Chemistry to Support Physiology-Based

Pharmacokinetic Studies. Because many of the

contaminants that affect marine mammals are

lipophilic, they tend to be stored mainly in the

blubber of pinnipeds and cetaceans. However, the

ways in which lipid profiles in the blubber change

during the year, by age or reproductive status or

within the blubber layer itself, are poorly understood. Understanding of lipid and blubber chemistry must be improved if we wish to model contaminant pathways in marine mammals.

It is fortuitous that blubber biopsies provide data on

many of the known xenobiotic compounds that raise

health concerns. New contaminants that enter the

oceanic system, however, may not be lipophilic.

This would mean that blubber samples obtained

from living cetaceans with a high-velocity dart and

from pinnipeds with a simple needle are of no use

for assays of these new contaminants. If a critical

class of new compounds were muscle-specific, for

example, how would samples be obtained? As new

compounds are introduced to the marine environment, it will be necessary to determine their preferred sites of deposit so that effective and accurate

sampling methods can be developed. As discussed

previously, blood may be an appropriate tissue for

sampling “short-lived” contaminants.

(4) Development of New Biomarkers for Rapid,

Inexpensive, and Practical Screening of Response

Biochemistry in Marine Mammals. The suite of

biomarkers currently available for assessing contaminant exposure should be examined systematically and applied whenever useful to marine mammals. However, additional research is needed to

develop sensitive, rapid, inexpensive, and field--

adaptable biomarkers. Many of the procedures

required for biomarker or contaminant samples are

difficult to follow in field conditions. Furthermore,

the assay costs can be restrictive. The net result is

that the needed samples may not be taken, and when

they are, they may never be analyzed. If biomarkers

could be developed for tissue or blood samples that

are easily obtained, stored, transported, and assayed,

this would improve our ability to measure contaminant responses in non-laboratory situations.

Suggestions Regarding Existing

Monitoring and Research Programs

Several existing research or monitoring programs

can be used to address the issues and meet the needs

identified above. Here we discuss six approaches

that should be considered for enhancing the effectiveness of these programs with regard to measuring

adverse effects of contaminants on marine mammals.

(1) Forge Collaborations between Marine

Mammal Scientists and Ongoing Medical and

Environmental Programs Designed to Quantify

Contaminant Effects, Regardless of Whether

These Involve Marine Species. The quantification

of contaminant effects is well-established in the

fields of medicine and environmental chemistry.

Marine mammal scientists should be encouraged to

establish collaborative links to programs in these

fields. In the United States, such links could come

from programs formally cosponsored by the National Institutes of Health or the Environmental

Protection Agency and the Marine Mammal Commission or the National Marine Fisheries Service.

Special training grants could be established for

marine mammal scientists to work in appropriate

medical or environmental laboratories. Numerous

other avenues exist for developing collaborations,

assuming that adequate support is made available by

the relevant agencies involved in marine mammal
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58

conservation.

(2) Develop Field Programs with Pinnipeds and

Cetaceans That Involve Longitudinal Aspects

and/or That Are Adaptable to Controls.

Well-established field programs involving pinnipeds

or cetaceans should be encouraged and supported to

develop collaborative projects on contaminant

issues. These programs offer the advantages of

multi-year databases on recognizable individuals

and/or access to large numbers of animals, whether

through capture-release, salvage of bycatch, or

ongoing directed killing operations.

For pinnipeds, some of the existing programs

involve harbor seals, elephant seals, and fur seals

worldwide, gray seals in the United Kingdom,

California sea lions in the United States, and Weddell seals in the Antarctic. All of these projects

include established infrastructure, long time-series

of data, and reliable access. With regard to cetaceans, the bottlenose dolphin projects in the southeastern United States and at Moray Firth, Scotland,

offer opportunities to work with free-ranging yet

well-known individual animals. Both projects have

good infrastructure, long time-series of data, and

access. The beluga whale population in the St.

Lawrence River of eastern Canada should be the

subject of increased study. The bowhead and

beluga whales hunted off the north coast of Alaska,

minke whales taken in Japanese and Norwegian

whaling, gray whales hunted in Russia, and the

long-finned pilot whales killed in the Faroe Islands

might be sampled through collaborative agreements

with the appropriate hunting groups. These situations offer unique opportunities to obtain samples

from animals that could be well used in contaminant

studies.

(3) Use Captive Programs to Study Individual

Marine Mammals in Detail. Collaborative research agreements should be established with

facilities that maintain captive populations of

marine mammals. Such agreements can facilitate

in-depth studies of molecular biology, biochemistry,

physiology, reproduction, behavior, and health of

individual animals relative to contaminant exposure.

The controlled environments in these facilities could

provide opportunities for non-lethal experimentation

and serial sampling over long time periods and, in

some cases, across generations. Protocols should be

established to take full advantage of specific events,

e.g., sampling when an animal dies.

(4) Continue or Establish Marine Mammal

Health and Stranding Programs in Which Large

Numbers of Stranded or Rehabilitated Animals

Can Be Examined. Programs involving the

rehabilitation of stranded marine mammals should

include research relevant to risk assessment. The

animals in rehabilitation facilities represent a potentially valuable resource for studies of contaminant

effects. Thus, allowance should be made for wellconceived studies using these animals. Animals in

rehabilitation facilities might be used to identify

health responses in situations where all potential

risk factors other than contaminant exposure can be

ruled out. Studies could be conducted in which

contaminant loads and health are monitored as the

animals are provided with “cleaner” food than is

available in local waters. Consideration should be

given to using animals in rehabilitation facilities

particularly in circumstances where by-caught or

hunted specimens are unavailable. Individuals that

are fully rehabilitated would be preferable subjects

for some studies; caution and careful design would

be required to interpret results from animals that are

seriously compromised by illness, injury, or acclimation to captivity.

(5) Focus the Sampling of Stranded Marine

Mammals to Address Specific Research Questions. Stranded animals provide opportunities to

sample a variety of tissues and collect data that can

be used to evaluate contaminant effects. Currently,

one of the major problems associated with sampling

efforts is the lack of consistent protocols within and

among the organizations that investigate strandings.

All too frequently, the information collected is

insufficient for interpreting contaminant data. Most

of the organizations operate with inadequate funding, which limits sampling efforts and follow-up

analyses. Responsible agencies should identify

specific tissue needs, collection and handling protocols, necropsy procedures, and histopathological

and toxicological analyses. Training in these
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

59

protocols should also be offered. In the United

States, this effort could be coordinated through the

NMFS Marine Mammal Health and Stranding

Response Program. The effort should recognize and

reflect the responsibilities of state agencies as well

as U.S. federal agencies such as the U.S. Fish and

Wildlife Service, the Environmental Protection

Agency, and the National Oceanic and Atmospheric

Administration.

(6) Standardize Protocols for Sampling Marine

Mammals During Live-Capture Operations in

Order to Facilitate Comparisons over Time and

Across Study Sites. Live-capture operations

provide unique opportunities to obtain samples from

cross-sections of free-ranging populations. While

specific research goals may differ from program to

program, standardized protocols for collection and

handling of a basic set of tissues for contaminant

studies are needed to facilitate valid comparisons.

In the United States, such standardization could be

established and coordinated through the Marine

Mammal Protection Act permit process (NMFS and

U.S. Fish and Wildlife Service) and by coordination

and planning meetings held by regional organizations. 
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

60

Surrogate Approaches Subgroup Report

Subgroup Members: Colborn, Ross, Schwacke

(Rapporteur)

Issue Title: Surrogate Approaches to

Assessing Contaminant Effects on Marine

Mammals

Issue Description and Rationale:

Why Is This Issue Important? Establishing

cause-and-effect relationships between contaminants and marine mammal health or reproductive

success is very difficult in the current legal and

ethical paradigms. In the absence of conclusive

studies on marine mammals themselves, the use of

surrogate models can help overcome many of the

uncertainties about such cause-and-effect relationships. Studies of surrogate models can provide

insights about mechanism of action, the comparative

risks presented by different chemicals, and dose-respon

se relationships. In addition, control of experimental conditions makes it possible to eliminate confounding factors and reduce variability within

treatment groups, thus providing the statistical

power necessary to detect effects. The greater

availability of species-specific reagents and the

ability to carry out invasive studies represent additional advantages of using surrogate models. The

selection of an appropriate surrogate model depends

on the question being posed and the endpoint being

assessed. For example, laboratory rodents may be

useful for many endpoints, including immunotoxicolo

gy, but a mustelid might be preferred for studies of

delayed embryonic implantation in pinnipeds.

Surrogate studies and studies of marine mammals both need to draw upon the extensive mammalian toxicology literature. The usefulness of information generated from studies of surrogate models

will depend upon certain assumptions and extrapolations. It is important to be aware of the assumptions and to critically evaluate the extrapolations at

all stages of the research. While it is not necessary

to address all unknown factors in surrogate study

designs, it is essential to consider all of those that

may affect extrapolation. For example, it is important to consider differences in exposure route, dose,

metabolism, genetics, physiology, reproductive

strategy, dietary composition, and sensitivity between a marine mammal in question and a surrogate

species. Also, one needs to bear in mind the difference between chronic and acute toxicity. Ultimately, a combination of surrogate and marine

mammal studies is needed to evaluate the risks from

effects or potential effects of contaminants on

free-ranging marine mammals. Sufficient information is not, and will not be, available solely from

studies of marine mammals.

Evidence from both wildlife and laboratory

studies identified a link between prenatal exposure

to certain contaminants and urogenital development

in males, thus flagging this issue for human health

authorities. As a result, the Centers for Disease

Control and Prevention (CDC) searched public

health registries, hospital records, and other databases to estimate the incidence in the United States

population of hypospadias, a visible impairment of

the urogenital tract at birth in males. This condition

is determined between gestation days 56 and 80 in

humans and days 15 and 20 in the rat. The CDC

reported a doubling of hypospadias in the U.S. male

population between 1970 and 1990, to a 1990 rate

of 1 in 125 male births (Paulozzi et al. 1997). This

example supports the principle of using surrogate

species to identify problems that might be present in

marine mammal populations, but easily overlooked

at the individual level. 

What Is Generally Known about This Issue?

Mammals are remarkably similar in many fundamental aspects of physiology. Their immune

systems, endocrine systems, and reproductive

physiology share many features. Evolutionary

adaptation to different habitats has resulted in a

great diversity of sizes and shapes within the mammals, but some of the physiological differences

remain relatively minor. These include, for example, differences in cell-surface markers for leukocytes, or implantation strategies (e.g., direct vs.

delayed implantation). Other differences may be

more profound (e.g., in the organism’s metabolic

capacity to eliminate xenobiotics). Even these,
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

61

however, can be a question of degree rather than the

presence or absence of a particular system. The

similarities in physiological systems within mammals are greater than the dissimilarities, thereby

allowing interspecies comparisons and providing a

basis for the use of surrogate models. Assumptions

about similarity have formed the basis for the wide

use of rodent models in studying the potential

toxicity of new chemicals and drugs to humans.

Initial studies have shown that surrogate approaches

can also provide toxicological information relevant

to certain marine mammal issues

What, in General, Needs to Be Determined to

Resolve the Critical Uncertainties? No single

surrogate approach will be sufficient to explain the

effects of the many types of contaminants present in

environmental mixtures, or to elucidate the many

types of responses to those effects on the part of

organisms. Nor can surrogate studies be expected to

entirely replace well-designed studies of captive or

free-ranging marine mammals. Risk assessment for

marine mammals will require a critical consideration of the accumulated evidence from different

types of surrogate models (including humans), as

well as studies of both captive and free-ranging

marine mammals. Increased certainty about

mechanistic insights from surrogate studies must be

matched with increased ecological or “real world”

relevance associated with studies of marine mammals. Using the “weight of evidence” from both

types of studies, we will be better able to judge

whether ambient levels of contaminants are affecting (or present a risk to) free-ranging marine mammals. We should also be better able to identify the

chemical or class of chemicals which is having an

observed effect on (or presents the greatest risk to)

marine mammals.

Means to Resolve the Critical Uncertainties

Surrounding the Issue

(1) Interspecies Extrapolation. The use of a

surrogate species always assumes comparability of

effects between a marine mammal species and the

surrogate model in question. Extrapolation of

results from laboratory studies to conclusions about

effects on wild marine mammals requires critical

assessment, although the uncertainty introduced by

the extrapolation can be minimized through careful

experimental design and selection of surrogate

species. We have tabulated the more important

sources of uncertainty and possible ways of resolving them (Table 7).

(2) Complex Mixtures. Ambient levels and

patterns of contaminants in free-ranging marine

mammals challenge efforts to understand the risk to

these animals presented by specific chemicals. The

use of surrogate models allows for the resolution of

many critical uncertainties, with greater control over

exposure regimes (chronic vs. acute; complex

mixtures vs. simplified mixtures vs.single chemicals; comparability of TEFs among species). We

have outlined in Table 8 the main sources of uncertainty and proposed means to resolve them.

(3) Mode of Action. Establishing the mechanisms, or modes, of action for contaminants in

marine mammals is limited by ethical, logistical,

and methodological considerations. Surrogate

models allow for greater experimental control and

levels of invasiveness which are required to understand the mechanism of action of a particular chemical or mixture of chemicals (Table 9).

What Are the Likely Consequences If This

Issue Is Not Addressed?

The uncertainties surrounding this issue must be

addressed in order to provide a credible evaluation

of the effects of contaminants on marine mammals.
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Table 7. Important sources of uncertainty in extrapolating results of studies from various other

species to marine mammals, with potential means for their resolution

Source of Uncertainty

Differences in metabolic capacities

to deal with contaminants

Comparability of mechanisms of action

Comparability of physiological systems

Validation of model species

Exposure regime

Proposed Means to Resolve

Explore the utility of physiology-based

pharmacokinetic (PBPK) models to assess

compartmentalization, elimination, etc., of contaminants in different species. Compare P-450 profiles in

both surrogate and marine mammal species. 

Continue research to identify common mechanisms of

action between laboratory species and marine mammal

species. Examples:

• Identification and characterization of Ah receptor in

tissues of different species.

• PCB metabolites and disruption of vitamin A, thyroid

hormone and common carrier protein levels (e.g., in

harbor seals and rats).

• Common markers in reproductive endocrinology.

Consider phylogeny, ecology, physiology, and available information for the proposed surrogate species

prior to selection (e.g., delayed implantation as a

reason for using mustelid instead of rat as surrogate

for pinniped reproduction).

Identify endpoints common to both surrogate and

marine mammal species that may be predictive of

additional effects which are impossible to measure in

the marine mammal. Additional endpoints seen in the

surrogate model will then provide grounds for speculation and guidance in the design of studies of

free-ranging marine mammals.

Consider duration of exposure, mode of exposure and

lifestage(s) of subjects when designing experimental

studies.

Risk assessment involves the determination of

magnitude and probability of adverse effects related

to contaminant exposure. Assignment of probability requires the quantification of uncertainty related

to the estimation of effects, with decreased uncertainties resulting in more precise estimation of

probability bounds. Because the ultimate goal of

risk assessment is to provide the information necessary to make effective and informed risk management decisions, uncertainties must be minimized.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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Table 8. Important sources of uncertainty in interpreting significance of exposure to complex

mixtures of contaminants in marine mammals, with potential means for their resolution

Source of Uncertainty

Effect of complex mixture

Identification of chemical within mixture responsible for

primary toxicity of that mixture

Possible synergistic or antagonistic interactions

Applicability of TEFs (are the largely rodent-based

international TEF values applicable to marine mammals?)

Proposed Means to Resolve

Surrogate feeding studies (e.g., with laboratory rodents)

using relevant mixtures with appropriate dietary and

exposure controls.

Identify evidence from existing studies, including

laboratory and observational studies on terrestrial

animals, fish-eating birds, or other relevant species.

Perform single-chemical-class-exposure experiments

with appropriate model species. Use TEFs to delineate

relative risks of PCBs, PCDDs and PCDFs.

Use simplified mixtures to explore and determine

interactions (e.g., different combinations of PCB congeners, TBT with DDE, TBT with PCB126) in in vitro or

laboratory-rodent studies.

Conduct comparative studies among wildlife and

laboratory-animal species (e.g., using in vitro liver

enzyme induction).

Ignoring the power of surrogate models,

whether they be in vitro assays or experimental

exposures of rodents to chemicals, will result in an

endless debate about the hypothetical effects of

food-chain contamination on marine mammals. If

surrogate models are not used and existing information is ignored, we can expect a continued low level

of confidence regarding effects; a low capacity to

assess the chemicals with the greatest toxicities

(greatest risk); a minimal understanding of mechanisms of action; an inability to assess risk to most

cetaceans and to pelagic marine mammals generally

(logistics limit sampling opportunities); and a

diminished value of existing rodent literature.

Failure to resolve the critical uncertainties outlined

in the preceding section will result in a continued

lack of confidence in our ability to assess effects,

which will ultimately limit the usefulness of risk

assessment altogether.

Suggestions Regarding Existing Monitoring and Research Programs

(1) Study Design in Assessing Effects of Complex Mixtures. There are lessons to be learned

from existing studies on the effects of complex

mixtures on animal groups other than marine mammals. Such studies may call attention to important

contaminant issues, as was the case with DDT and

the extirpation or near-extirpation of piscivorous

birds from much of North America and Europe.

Some of them may also provide examples of surrogate models for marine mammals. In a broad sense,

these studies, or their methodological approaches,

include

C Single-chemical laboratory-animal studies

which identify problem chemicals and the

effects of these chemicals, and which give a
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

64

Table 9. Important sources of uncertainty in determining mechanisms of action of contaminants

in marine mammals, with potential means for their resolution 

Source of Uncertainty

Most mechanisms of action are not well understood.

Proposed Means to Resolve

Conduct studies using in vitro exposures of cell cultures

from marine mammals (e.g., tumor cell lines, kidney cell

lines, peripheral blood cells).

Conduct exposure studies using marine mammal immune cell-reconstituted Severe Combined Immune

Deficient (SCID) mice.

Share information from past or ongoing studies across

agencies.

mechanistic foundation to other studies (e.g.,

on marine mammals).

C New techniques which help to identify the

most potent contaminants in environmental

mixtures, using a toxic equivalency approach

(e.g., Ah- and estrogen-receptor mediated

toxicities).

C Captive feeding studies or egg injection/egg

painting studies in a laboratory setting (e.g.,

with mink, rats, fish-eating birds) based on

environmentally relevant exposures.

C Field-based studies of free-ranging populations of animals which incorporate different

levels of exposure (e.g., on river otters, fish-eating birds).

C Reviews of information already available on

economically important animal groups (e.g.,

fish, ducks, other migratory species).

C Nationwide studies (e.g., in the United Kingdom or the United States) which address

estrogenic activity in freshwater and coastal

fishes.

C International research related to the issue of

amphibian deformities and declines.

C The few important long-term monitoring

studies of contaminants in sentinel species,

such as the Herring Gull Monitoring Program in the Great Lakes.

(2) Institutional Issues Related to Assessing

the Effects of Contaminants. In response to

worldwide concern about the growing number of

chemicals that are biologically active, the Environmental Protection Agency has a Congressional

mandate to produce, by the year 2000, a set of in

vitro and in vivo screens and assays to test synthetic chemicals for their possible endocrine-disrupting effects. This battery of tests will certainly

not detect all of the possible mechanisms by which

chemicals can interfere with development and

reproduction. However, it is a start, and anyone

designing models to predict negative effects of

chemical exposure on marine mammals should

follow closely the EPA’s progress with this program.

Concurrent with the EPA initiative, an ad hoc

interagency cooperative effort among the National

Toxicology Program, the National Institutes of

Environmental Health Sciences, the Food and Drug

Administration, and EPA has developed a set of

protocols for low-dose testing at physiologically

and environmentally relevant ambient exposure

levels. These multi-generational assays were

designed to detect cryptic, long-term, or delayed

effects on function. They include more sensitive

endpoints than those used in traditional toxicology.

In essence, this development is establishing a new

discipline within the field of functional teratology.

The new assays have revealed a number of developmental and reproductive effects of widely used
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

65

chemicals not previously reported.

There is a role for the National Science Foundation and other funding entities to support the

basic research needed to determine where, when,

and at what levels endogenous hormones control

development and reproduction in marine mammals.

This kind of information on laboratory animals

provided insight into the fragility and sensitivity of

the embryo and fetus, thus demonstrating the

considerable utility of surrogate approaches to

toxicology.
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Case Study Subgroup Report

Subgroup Members: Aguirre, DeMaster, Matta

(Rapporteur), Reif

Issue Title: Case Study — Contaminants in

California Sea Lions off Southern

California

Issue Description and Rationale:

This case study had two purposes. One was to

illustrate how components of an ecological risk

assessment approach can be used to evaluate the

threat of persistent contaminants to marine mammals. The other was to identify critical uncertainties

in available information. It was assumed that these

uncertainties would become evident as we attempted

to actually complete a risk assessment on a selected

marine mammal species. The risk posed by organo

chlorine contaminants to the California sea lion was

chosen because this species has been relatively well

studied and because risk-management decisions are

actually pending with regard to contaminated

sediments in the area. The case study follows the

EPA ecological risk-assessment framework. It was

developed using information available during the

workshop and is therefore not complete.

Problem Formulation

Background. This risk assessment evaluates the

potential ecological effects of DDT and PCBs on

California sea lions. Beginning in the late 1960s,

reproductive problems were observed at breeding

colonies in southern California (De Long et al.

1973). At about the same time, information became

available regarding the potential effects of DDT on

reproduction, and the extent to which DDT was

being discharged into the marine environment from

local manufacturing sources. (In this case study, the

term DDT refers to the sum of DDT and its metabolites, often referred to elsewhere as DDTs or EDDT

). PCB concentrations mentioned here were generally quantified on the basis of common Aroclor

mixtures. Unless otherwise specified, concentrations in sediments are stated in terms of dry weight,

while tissue concentrations are expressed in terms of

wet weight.

PCBs, DDT, and other contaminants were

released into the marine environment of southern

California primarily through sewage discharges

along the Palos Verdes Shelf. These discharges

began in 1937 and continue to the present. Large

quantities of DDT were discharged through these

outfalls as a result of pesticide manufacturing

operations in the area between the late 1940s and

the early 1970s (Mearns et al. 1991). PCBs from

more than 7 sources in the Los Angeles area were

also discharged through these outfalls and have

resulted in widespread contamination. These

contaminants associate with organic particles and

persist for decades in the environment. According

to Science Applications International Corporation

(1998), discharges of these contaminants have

declined dramatically over the last 30 years (from

more than 100 tons per year of DDT in the late

1960s to 0.03 tons per year in 1985), but large areas

of contaminated sediments remain. DDT concentrations in surface sediments currently exceed 1 ppm

over 42 square kilometers of the Palos Verdes Shelf.

Concentrations in sediment have declined since the

1970s by a factor of between 3 and 10, but concentrations of up to 91 ppm remain in surface sediments

in some locations. PCB concentrations in sediments

exceed 3 ppm around outfall discharges (Science

Applications International Corporation 1998).

California sea lions in U.S. waters are managed

by the National Marine Fisheries Service as a single

population (i.e., stock) under the terms of the

Marine Mammal Protection Act . Their population

history and population dynamics are well known

(Boveng 1988, Lowry et al. 1992, Barlow et al.

1997). Their numbers were severely reduced due to

directed human management actions (i.e., intentional killing and bounty programs to reduce California sea lion numbers and promote the recovery of

important commercial fisheries) late in the 19th

century and early in the 20th century. The number

of sea lions in California may have been as low as

5,000 animals at some point earlier in the present

century. By mid-century, the recovery of the
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

67

population off California was well underway, with

numbers reaching tens of thousands. Between 1984

and 1992, this population continued to increase at

an annual rate of 5-8% per year. The current population likely includes 150,000 to 200,000 animals.

Estimates of carrying capacity are not available for

this species; therefore, it is not possible to specify

the population level at which the net rate of increase

will be zero (i.e., a stable population). It is very

likely that the population rate of increase will

decline during the next 25 years. 

California sea lions have well-established

breeding colonies in the California Channel Islands.

They feed primarily on pelagic schooling fish (for

example, anchovy, sardine, rockfish, and hake) and

squid but are also known to eat a wide variety of

other fish. Females and pups remain near the

breeding grounds, where they presumably continue

to be exposed to contaminants in food, while males

can migrate long distances during the non-breeding

season. 

Contaminants of Concern. Although a number of

contaminants are present in the marine environment

of southern California (including trace elements and

PAHs), this risk assessment focuses on DDT and

PCBs. There is a large body of evidence that

exposure to these contaminants is associated with

adverse effects in a wide variety of species. Relevant information on the environmental chemistry,

fate, and adverse effects is summarized in this

section.

DDT and its degradation products, DDE and

DDD, are not easily metabolized by microorganisms

in the environment. DDT compounds are highly

lipid-soluble, bind to organic matter in sediments,

biomagnify, and persist for years in the environment. DDT compounds can be detected in filtered

water samples, but are also associated with suspended particles. Depuration rates for DDT compounds are reported to be low, but they vary among

species. 

Although exposure to DDT can have acute lethal

effects, sublethal chronic effects are much more

common. Chronic effects of DDT and its metabolites include alterations in behavior and reproduction, which are thought to be the result of hormonal

alterations, enzyme-system alterations, and alterations in calcium metabolism (Science Applications

International Corporation 1998). DDT is known to

disrupt reproduction in freshwater and marine fish,

reducing fecundity, decreasing fertilization success,

and reducing hatch success and larval survival

(Hose and Cross 1994) at concentrations exceeding

about 1 ppm (wet weight) in fish tissues. Reproductive problems in birds have also been associated

with DDT exposure. DDT also has been associated

with reduced immune-system function in fish

(Science Applications International Corporation

1998). Within the past five years, it has been shown

that DDE is a powerful anti-androgen (Kelce et al.

1995) and an anti-prostaglandin (Lundholm 1995,

1997). In humans, DDE has been associated with

reduced milk production and a shortened lactation

period at concentrations exceeding 3 ppm in maternal lipids (Rogan and Gladen 1985, Rogan et al.

1987, Gladen and Rogan 1995). PCBs can also

adversely affect mammals (Safe 1994).

Each of the 209 PCB congeners differs in the

number and position of chlorine atoms on the

biphenyl ring, resulting in variable toxicity and

persistence in biota. The relative persistence of

PCBs generally increases with increasing chlorination. Compounds with few chlorines are thought to

degrade rapidly. PCBs adsorb tightly to sediment

particles and are lipid soluble. Some PCBs are

metabolized by some species, and many are stored

in lipid-rich tissues. Some PCB congeners can be

excreted or eliminated during reproduction. They

biomagnify and can be found at high concentrations

in species at higher trophic levels. 

Some PCB congeners can be acutely and directly toxic, but concerns about PCB toxicity are

primarily related to chronic sublethal effects. PCBs

are considered reproductive toxicants in fish, with

reduced spawning success, reduced hatch success,

and reduced larval survival. PCBs have also been

associated with impaired immune-system function

in fish and marine mammals. There is also recent

evidence that some PCB metabolites could disrupt

endocrine systems. Some PCB metabolites bind to

the rat estrogen receptor (Korach et al. 1988).
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

68

Exposure to PCBs in combination with other contaminants has been associated with neoplasms in

fish (Myers et al. 1998, Stehr et al. 1997, Varanasi

et al. 1992). Johnson et al. (1998) found that in

utero exposure to background levels of PCBs and

their co-contaminants contribute to neurobehavioral

and developmental deficits in newborns. These

differences persist through school age.

Conceptual Model. (Pathways for contamination

to reach target organisms: sediment ö invertebrates

ö fish ö sea lions.) Because California sea lions

inhabit an area where sediments and fish are known

to be contaminated with persistent, bioaccumulative

organochlorine contaminants, the most significant

pathway of exposure is likely through consumption

of contaminated fish. Because the contaminants

involved are known to disrupt reproductive- and

immune-system function, and because there is

recent evidence that these contaminants can cause

effects such as cancer, the following assessment

endpoints have been selected for this risk assessment:

C estimate risk of adverse reproductive outcomes

in California sea lions due to contamination;

C estimate risk of cancer associated with exposure

to contaminants in California sea lions;

C estimate risk of adverse immune-system effects

in California sea lions due to contamination.

These assessment endpoints contain explicit

expressions of attributes of the population of California sea lions that should be protected: reproductive output, survival, and immune-system function.

They were selected based upon available information regarding the modes of action of the contaminants of concern. The three assessment endpoints

can be evaluated using the following measurements:

(1) direct measurements of adverse effects in California sea lions; (2) concentrations of contaminants

in tissues of California sea lions; (3) concentrations

of contaminants in fish and sediment from the area

of concern; (4) threshold concentrations of contaminants found in laboratory or field studies to be

associated with adverse effects (preferably from

other pinniped species, but from other species such

as rodents, if necessary and appropriate); and (5) if

alternate species are used, creation of a food-web

model to estimate the “dose” to sea lions to compare

with data from experiments with other species.

A “weight of evidence” approach will be used to

evaluate potential risk to California sea lions from

organochlorine contaminants. Greatest weight will

be given to actual measurements of adverse effects

in these animals, if effects can be correlated with

exposure concentrations. If actual measurements of

adverse effects in California sea lions are not available, information from studies of other species can

be used to predict the likelihood of adverse effects.

These might include captive studies on other pinniped

s, or laboratory studies on rodents if diet, exposure

route, metabolism, physiology, and reproductive

strategy are considered sufficiently similar.

Exposure of California Sea Lions to PCBs

and DDT

Two basic approaches are available to estimate

exposure of California sea lions to PCBs and DDT.

The first involves analyzing sea lion tissues from

the area to determine body burdens and tissue

residues. The second includes analysis of contaminants in prey and calculations of “doses” from

expected food consumption.

Exposure data for anthropogenic contaminants

in California sea lions are available from several

sources. There are at least eight reports of contaminants sampled between 1969 and 1992, with the

vast majority from California sites. Analyses have

included primarily DDT, DDE, and PCBs from

approximately 150 animals (O’Shea and Brownell

1998). Recently, additional data were collected

from California sea lions that died after live stranding, including a subset of 25 animals that died from

acute trauma (Gulland et al. 1996). The tissues

were analyzed for chlordanes, PCBs, DDTs, and

aromatic compounds (e.g., PAHs) (Stein, personal

communication). 

Because all California sea lions return to the

Channel Islands to breed, and females and pups

remain near the breeding grounds, it is difficult to

establish reference conditions. All sea lions would
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

69

be expected to have been exposed to these contaminants to some degree. The lack of a control (relatively clean) population makes risk assessment a

difficult task for this California sea lion population.

However, data can be compared within subpopulations and age/sex cohorts. In establishing a link

between exposure and effects, a gradient of contamination should be examined, if possible. This might

involve collecting males close to and far from the

areas of highest sediment contamination, or examining old vs. young females, who might be expected

to vary in their levels of accumulated contaminants.

California sea lion prey are also contaminated

with PCBs and EDDT. Concentrations of DDT in

fish currently range up to 20 ppm or more (dry

weight) (Brown et al. 1998), although they have

declined dramatically since the 1970s. Data on

concentrations of these contaminants are not available for all prey species. The most highly contaminated fish species include white croaker and dover

sole, but these species do not constitute a large

proportion of the diet of California sea lions

(Antonelis and Fiscus 1980, Lowry et al. 1990,

1991). Nevertheless, concentrations of PCBs in

white croaker have exceeded 4 ppm in some areas

(Science Applications International Corporation

1998), whereas concentrations of DDT and PCBs in

rockfish in comparison (a favored prey item of

California sea lions) are approximately 10 times

lower than those found in white croaker. Although

anchovy (which are another favored prey item for

California sea lions) have not been sampled recently, in the 1960s they contained up to 13 ppm

total DDT; concentrations fell, however, during the

1970s (Anderson et al. 1975).

 

Effects of PCBs and DDT

Two lines of evidence can be examined for adverse

effects on California sea lions. The first includes

direct measurements of effects such as reproductive

impairment or prevalence of carcinoma in California

sea lions exposed to DDT and PCBs. Such direct

measurements cannot separate the contributions of

effects related to PCBs from those related to EDDT,

because these contaminants co-occur in marine

mammal tissue, prey items, and sediment throughout the area. Effects in sea lions would be evaluated

on the basis of data collected from sea lions in

several ongoing or recent studies, with the expectation that the total sample would include animals

representing a gradient of exposure. This gradient

would be used to assess the correlations between

exposure and effects. The second approach relies

on modeling to extrapolate from studies on species

other than marine mammals. A theoretical approach

to modeling is described here in lieu of a completed

model, which was precluded due to time limitations

at the workshop.

Studies of adverse effects of feeding DDT or

PCB compounds to rodents are quite common. In

order to apply the results of these studies to California sea lions, the following approach should be

taken: (1) determine the no-effect dose and loweffect dose for rodents for the endpoint in question;

(2) calculate the doses of PCBs and DDT obtained

by California sea lions feeding in contaminated

areas (by determining average and maximum concentrations of PCBs and DDT in prey species and

estimating the quantity of prey consumed); (3)

compare the doses in rodent studies (adjusted for

body weight) to exposures received by sea lions

(consider whether an extrapolation factor should be

applied to account for the uncertainty due to species

differences); and (4) conclude by reasoning that if

marine mammal doses exceed rodent effect doses

(toxicity reference values), then risk is indicated.

An alternate approach would be to convert toxic

doses in rodents to toxic body-burden threshold

concentrations in rodents. Tissue concentrations in

relation to average lipid content in rodents would be

compared to blubber concentrations in sea lions

(using uncertainty factors, where appropriate, to

account for species differences).

Effects on Reproduction. Elevated organochlorine

concentrations have been associated with premature

births in California sea lions, although cause-and-effe

ct relationships have not been established (O’Shea

and Brownell 1998). The initial study associated

stillbirths and premature pupping in California sea
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

70

lions with high concentrations of organochlorines

(DeLong et al. 1973). In sea lions sampled in 1970,

concentrations that averaged 824 ppm DDT and 112

ppm PCBs in maternal blubber were associated with

premature births. Mothers with normal term pups

had mean concentrations of 103 ppm DDT and 17

ppm PCBs in blubber (DeLong et al. 1973). However, further research provided evidence that diseases, including leptospirosis and calicivirus infections, were also associated with the phenomenon of

premature pupping (Smith et al. 1974, Gilmartin et

al. 1976). Although it has not been conclusively

demonstrated that the California sea lion population

has been adversely affected by high exposure to

DDT and PCBs, experimental evidence has shown

that mixtures of organochlorines in the diet, including PCBs and EDDT, can impair reproduction in

harbor seals during experimental situations

(Reijnders 1986). Reported differences in DDT

concentrations in 12 male California sea lions

sampled in 1970 and seven males sampled in

1988–1992 were enormous, suggesting that a real

reduction in organochlorine levels has occurred.

Differences in the average ages of animals from the

two samples could also explain in part the apparent

changes in DDT concentrations, but information on

the history of individuals (e.g., geographic foraging

patterns, ages) from the more recent samples were

not reported.

Cancer in California Sea Lions. Evidence linking

anthropogenic contaminants to increased occurrence

of neoplasms in marine mammals is sparse. A high

incidence of neoplasms has been reported for the

population of beluga whales in the St. Lawrence

River, and these whales have been found to have

higher concentrations of contaminants (including

PCBs, other organohalogens, and metals) than

beluga whales from less polluted high-latitude

environments. St. Lawrence belugas also exhibit

impaired reproductive and immune function (Béland

et al. 1993, De Guise et al. 1994, 1995). Increased

prevalence of hepatic neoplasms and related lesions

are also found in fish inhabiting areas with high

sediment concentrations of contaminants, including

PCBs (Harshbarger and Clark 1990, Bowser and

Martineau 1990, Hayes et al. 1990, Myers et al.

1991). 

Recently, an 18% prevalence of neoplasms, the

highest recorded to date in a pinniped population,

was reported in California sea lions that stranded

alive along the central California coast (Gulland et

al. 1996). The specific neoplasm is thought to be of

transitional-cell origin, and it occurs in the urogenital tract of young adults of both sexes (Gulland et al.

1996). Although the etiology of this carcinoma is

unknown, chemical contaminants may play a role.

One of the objectives of the present risk assessment

is to assess the likelihood that the concentrations of

contaminants, especially organochlorines (i.e.,

chlordanes, PCBs, and DDTs) and polycyclic

aromatic compounds (i.e., benzopyrenes), found in

sea lions are associated with an increased prevalence of transitional-cell carcinoma. It is known

from rodent studies that these compounds have the

potential to cause tumors.

Immunotoxicity. California sea lions inhabiting

polluted coastal areas are known to accumulate high

levels of organochlorines, which have been related

to the occurrence of several immune-system abnormalities. These persistent lipophilic contaminants

have been shown to adversely affect the immune

system, leading to immunosuppression and in some

cases increased susceptibility to infectious diseases

in laboratory animals. De Swart et al. (1994) and

Ross et al. (1996a) found that natural killer (NK)-

cell activity and mitogen-induced proliferative

T-cell responses were impaired in harbor seals fed

fish from the Baltic Sea, which were more highly

contaminated with PCBs and other organochlorines

than “control” fish from the Atlantic Ocean. In

addition, an increase was observed in polymorphonucle

ar granulocytes, possibly suggesting an increased

incidence of bacterial infections in the more contaminated Baltic Sea group (De Swart et al. 1994).

Further studies demonstrated that seals fed Baltic

Sea fish for two years had TEQ values 3.4 times

higher than seals fed relatively uncontaminated fish

from the Atlantic Ocean (Ross et al. 1995). These

studies also demonstrated a contaminant-related

suppression of delayed-type hypersensitivity and

antibody responses in the seals fed fish from the

Baltic. Contaminant levels (total PCB and TEQ)
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

71

were higher in many harbor seal populations in

northern Europe at the time of the phocine distemper virus epizootic than the levels observed in the

immuno-suppressed seals from Ross et al.’s (1995)

study. It was speculated that contami

nant-associated immunotoxicity in free-ranging

harbor seals may have contributed to the severity of

the epizootic (Ross et al. 1996b). T cells are important in the memory-based control of virus infections

(i.e., the “learned” ability of these cells to recognize

and attack cells infected by a pathogen which they

have previously encountered, or “specific immunity”) and in the overall immune response, while

NK cells are important in the early clearance of

virus infections in the absence of memory.

Risk Characterization

California sea lions are exposed to DDT and PCBs,

as evidenced by accumulations of these compounds

in blubber and other tissues. Data required for risk

assessment with respect to reproductive outcomes

and cancer may be obtained from several sources.

The evidence available from marine mammals is

limited, and in some instances controversial. Reijnde

rs (1986) fed female harbor seals fish that were high

or low in organochlorines and observed lower

pregnancy rates in those with the more contaminated diet (daily intake of approximately 1.5 mg

PCB). Inferences about impaired reproduction

based on observational studies, such as those involving ringed and gray seals in the Baltic Sea

(Helle et al. 1976a,b) and California sea lions

(DeLong et al. 1973), need to be qualified because

it is not possible to control for extraneous variables

such as concurrent infectious diseases. Also,

conclusions from such observational studies may be

biased by the reciprocal effects of impaired

reproduction on contaminant burdens. Given the

limited database available for risk assessment from

other pinniped species, data from experimental

laboratory animals such as rodents will be required

for dose-response estimation of effects. The

uncertainty surrounding extrapolation of rodent data

to pinnipeds will need to be factored into risk

characterization.

Similarly, the evidence for effects of

contaminants on cancer risk or on reliable markers

for cancer risk in pinnipeds is extremely limited.

Some use has been made of assays for induction of

cytochrome P450 enzymes, induction of mutant

oncogenes, and DNA adducts to substances such as

benzo-"-pyrene. However, the predictive value of

these markers is uncertain, and they are not

considered reliable indicators of cancer risk.

Therefore, dose-response data from rodent models

will also need to be included in the risk

characterization for cancer endpoints.

In a “weight of evidence” approach,

epidemiologic evidence from the target population

can contribute to the overall assessment of risk. For

example, tissue concentrations of DDT, PCBs, and

polycyclic aromatic compounds (PACs) are being

compared between stranded animals with

transitional-cell tumors and those with other,

non-neoplastic disorders (Stein, personal

communication). This approach can be used

directly for risk assessment, provided that

potentially confounding variables such as age, sex,

pregnancy, stage of lactation, etc. are appropriately

controlled and that technical issues regarding

accumulation of xenobiotics in affected-animal

tissues are resolved. However, the usual approach

in assessing causality for environmental

contaminants and disease requires replication in

other populations, determination of temporal

sequence, and adequate biological plausibility, all of

which may be difficult to achieve. Thus,

complementary information, based on other forms

of evidence, should be incorporated into risk

characterization in order to expand the framework

for risk-management recommendations. 

Uncertainty Analysis. There is considerable

uncertainty involved in characterizing the risk posed

by persistent contaminants to the U.S. population of

California sea lions. Therefore, it is critical that the

risk-characterization process incorporate uncertainty

in a precautionary manner. That is, as uncertainty

in components of the process increases, or as overall

uncertainty increases, proposed management actions

should become more risk-averse. Several

approaches have been reported in the literature.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

72

These include the use of (1) a multiplier (e.g., a

factor of 10 or one-tenth) in establishing thresholds

for one taxon based on laboratory studies from

disparate taxa; (2) the 10th or 90th percentile for

one or more of the input parameters in modeling the

potential adverse effects; (3) Bayesian or Likelihood

techniques that produce prior distributions for

output parameters of interest, where management

decisions are based on either conservative

interpretations of posterior distributions or objective

loss functions; and (4) simulation studies that

incorporate uncertainty into the process of “tuning”

the output to meet specified management objectives.

Given the arbitrary nature of the first two

approaches, efforts should be made to incorporate

uncertainty objectively, as is done when using the

latter two approaches. As noted earlier, uncertainty

exists in virtually all of the input parameters used to

characterize risk, such as uncertainty in quantifying

the dose-response relationship for specific age and

sex classes of sea lions, the number and magnitude

of chemicals to which sea lions are exposed, and the

degree to which density-dependent life history

responses confound our ability to detect

contaminant-related changes in survival and

reproduction. In addition, there is uncertainty in

other, less obvious input parameters, such as stock

structure (i.e., rates of exchange between sea lions

in Mexico and U.S. waters), seasonal aspects of the

dose-response relationship, and age- and

sex-specific responses to specific contaminant

levels.

Interpretation of Ecological Significance. One

problem in trying to evaluate which measures of

response to contaminants are most important has to

do with the current dynamics of the California sea

lion population and the risks from other factors.

This risk assessment attempts to identify additional

risks to the population from exposure to

contaminants. The population abundance has been

increasing for more than 40 years. How the

population is responding to the short-term effects of

the recent El Niño event is unknown. However, it

is anticipated that the population will respond as it

did to the major El Niño in 1983. That is, after a

few years, pup production will start to increase

annually, and after 3-7 years, the population will

have recovered to its pre-El Niño level and continue

increasing. Therefore, unless the effects of

contamination on survival and reproduction of this

population are unexpectedly severe, any adverse

effects due to contamination will likely be reflected

in a slowing of the population rate of growth.

Unfortunately, as the population continues to

increase toward its carrying-capacity level, the

population rate of growth will decline until it

reaches zero. Because of this situation, a slowing in

the observed growth rate of California sea lions

cannot be taken as conclusive evidence that

persistent contaminants are adversely affecting this

population. Rather, it will be necessary to estimate

the expected reductions in reproduction or survival

to determine the likely impacts of contaminants on

California sea lions.

Despite the lack of definitive scientific evidence

of a causal relationship between contaminant levels

and effects on reproduction or survival in California

sea lions, there are studies suggesting that

organochlorines have adverse effects on other

marine mammals. These studies support the

hypothesis that organochlorine exposure has

increased the susceptibility of sea lions to diseases,

including those that can cause abortions and other

endocrine disorders. It is evident that much more

research is needed to understand the ecological

significance of persistent contaminants and their

role in relation to other factors, including changes in

prey availability, infectious diseases, algal blooms,

global warming, El Niño and related events, and

population dynamics of the species of concern.

Qualitative and quantitative appraisals are needed of

the actual and long-term effects of organochlorines

and other contaminants. Both field studies and

toxicity tests with surrogate species can be used to

evaluate linkages between contaminant

concentrations and effects on ecological and

physiological receptors.

Field studies of California sea lions may confirm

the link between pollution and ecological effects.

Evidence can be obtained by investigating the

reduction of population size or the association of sea

lions with stressed habitats along the California
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

73

coast. More studies regarding community biodiversity and trophic structure may suggest answers

to some questions and help explain recent die-offs

possibly caused by domoic acid and other biotoxins.

Dose-response studies may link contaminants and

other etiologic agents to the incidence of tumors or

other lesions.

Summary 

Risk assessment is used to evaluate the risk posed

by a particular agent or agents to the health or

maintenance of a population, species, or ecosystem.

In this case study, we have attempted to highlight

the elements that should be included in a risk

assessment. We have used the population of

California sea lions in U.S. waters as the population

of interest. As noted in this example, risk

assessment requires the integration of information

on (1) current sources of exposure; (2) current

distributions and concentration patterns of the

contaminants of concern; (3) the dose-response

relationship for DDT and PCBs, derived either from

field studies of California sea lions or from wholeanimal field and laboratory studies of other

pinnipeds (or other mammals); and (4) mechanisms

by which contaminants can compromise the survival

or reproduction of model species, obtained from in

vitro cell-culture studies. Our relatively cursory risk

assessment indicates that DDT and PCBs may pose

considerable risks to the population of California

sea lions in U.S. waters. This conclusion is based

on a preponderance-of-evidence approach

(sometimes referred to as the “weight of evidence”

approach) in the absence of detailed, controlled

dose-response studies using California sea lions as

the study subjects. Such an approach is

precautionary and scientifically defensible. Finally,

we have not included in this report a detailed

section on the relative merits of a suite of actions

directed at mitigating the effects of contaminants on

California sea lions (often referred to as a riskmanagement evaluation). Such an evaluation would

require better information on current sources,

exposure levels, and dose-response relationships,

including those for dose levels considerably lower

than those observed in the early 1970s.

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Working Group on Future Trends

Working Group Members: Fair, Geraci (Leader),

Goldberg, Jarman, Kucklick (Rapporteur), Krahn,

Muir, Norstrom, Phinney, Tanabe, van Leeuwen,

York.

This working group did not divide into subgroups,

and its report consists of a unified document in a

format somewhat different than those of the other

working groups. The group considered four major

topics: (1) projected “new” contaminants of future

concern; (2) future trends with contaminants currently known to be issues for marine mammals; (3)

future needs to improve and insure consistency of

sample collection and analysis; and (4) future

management needs.

Background and Rationale

The problems of persistent organic pollutants will

remain well into the foreseeable future. A general

decline in levels of persistent organic pollutants in

the marine environment is not anticipated. There is

every likelihood that the environmental trends of

halogenated organic compounds, such as polybrominated diphenyl ethers and chlorinated paraffins, will parallel production trends, as demonstrated

with well known chemical contaminants such as

PCBs (polychlorinated biphenyls) and DDT (dichlorodiphenyltrichloroetha

ne). While the environmental levels of some compounds may be slowly declining, many are still

within the ranges where subtle toxic effects are to be

anticipated. Trends in contaminants must be placed

in a regional context, and rates and directions of

change are often region-specific. For example, in

the Southern Hemisphere the concentrations of

PCBs appear to be increasing. The rates of change

of many compounds in the Southern Hemisphere are

poorly known, and this region may be at future risk.

Much of the research on contaminants and

marine mammals has focused on the problem of

persistent organochlorine chemicals such as PCBs

and DDT, which are a continuing and global problem. Potential problems caused by other persistent,

toxic, and bioaccumulative substances (PTBSs)

cannot currently be addressed due to the lack of

basic information on their production, use, exposure, and effects (Environmental Protection Agency

1998). It is currently estimated that there are rough

ly 2400 lipophilic and persistent chemicals, of

which 390 are PTBSs. In order to prevent longterm pollution from these largely unknown chemicals, chemical industries should disclose basic

information on such compounds, and this information should be made widely available. This will

require enhanced international cooperation, preferably within the existing framework of chemical

contaminant programs, such as the Existing Chemicals Program of the Organization for Economic

Cooperation and Development (1991) and the

Program on Persistent Organic Pollutants of the

United Nations Environment Programme (1998).

Monitoring studies are essential to the description and understanding of pollutants. It is necessary

to exploit existing analytical techniques to identify

as many anthropogenic compounds as possible in

marine mammal tissues in order to expand the

identification of existing and new chemicals that

accumulate in, and pose potential threats to, these

species.

“New” Contaminants of Future Concern

Persistent, Toxic, and Bioaccumulative Compounds Not on the Standard Persistent Organic

Pollutants (POPs) List That Are Used or Produced in Large Quantities. A number of compounds not on the standard POPs list are still used

or produced in large quantities. Examples include

polychlorinated naphthalenes and polychlorinated

diphenyl ethers; other examples are listed in the

International Whaling Commission’s Bergen workshop report (Reijnders et al. 1999). Organo-metallic

compounds such as tributyltin, although phased out

in many marine-oriented applications, are still used

in some areas.

Non-Persistent Chemicals That Could Present a

Risk to Marine Mammals Through Their High

Bioaccumulation Potential and Heavy or Wide-
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spread Use. This is a potentially very large group

of chemicals consisting of, for example, pesticides,

biocides, and pharmaceuticals.

Eutrophication and Biotoxins. Biotoxins from

algal species have been implicated in die-offs of

manatees (O’Shea et al. 1991, Bossart et al. 1998),

humpback whales (Geraci et al. 1989), dolphins

(Geraci 1989), seals (Banish and Gilmartin 1992),

sea otters (DeGange and Vacca 1989), and possibly

California sea lions (Anonymous 1998). These

events may be exacerbated by eutrophication in

coastal waters. One of the most pervasive marine

pollution problems on a global basis involves the

eutrophication (particularly the accelerating inputs

of nitrogen and phosphorus compounds) of coastal

waters via the atmosphere, rivers, and outfalls.

Eutrophication of coastal waters is continuous and

expanding. Consequent increases in plant productivity are evident from the increasing frequency and

geographic range of algal blooms (including toxic

algal blooms), anoxic and hypoxic zones in the

water column and sediments, and alterations to the

makeup of communities of organisms. These

consequences can affect marine mammals in the

following ways: (1) mortality through the ingestion

of toxic algae in foods; (2) alteration of their normal

food supplies through changes in the make-up of

their food webs; and (3) diminished oxygen in their

environmental waters (Hallegraeff 1993, Anderson

1995).

Polymers and Low Molecular Weight Monomers. These compounds are released in huge

quantities into the ocean, but their fate is uncertain.

Vinyl chloride is one example of a compound that

may be an emerging chemical threat.

Chemicals That Cause “Endocrine Disruption.”

Endocrine disruption remains a potentially important environmental problem and needs to be included in future marine mammal research. New

technologies should be developed to identify such

compounds and their effects on marine mammals.

Support of programs for compilation of information

on these compounds, including physical properties,

applications, and usage, is important for predicting

future trends. However, these chemicals are not

included as a separate category in this working

group report for the following reasons: (1) the

structural diversity of chemicals implicated as

“endocrine disrupters” is very large, and marine

mammal research is better served by focusing

research questions on specific chemicals and their

effects, including endocrine system effects; (2)

many suspected “endocrine disrupters” are included

under existing chemical headings (e.g., PCBs,

tributyltin, etc.); (3) for carnivorous marine mammals, metabolism of contaminants by prey species

such as fish confounds the ability to make a direct

connection between exposure to potential endocrine

disruptive chemicals and reproductive and developmental effects. 

Future Trends With Currently Known

Contaminants

The major classes of persistent organochlorine

contaminants bioaccumulating in marine mammals,

historically and at present, are PCBs, DDTs, toxaphe

ne, chlordanes, HCHs (hexachlorocyclohexanes),

and their metabolites. The relative distribution of

these substances may vary from one geographical

location to another and from inshore to offshore.

However, PCBs and DDTs are the groups of contaminants with the highest concentrations in marine

mammals almost everywhere. Low amounts of

many other organochlorines, such as dieldrin,

chlorobenzenes, mirex, chloroparaffins, PCNs

(polychlorinated naphthalenes), PCDDs

(polychlorinated dibenzodioxins), and PCDFs

(polychlorinated dibenzofurans) are often also

present. There may be locations where these contaminants accumulate to levels of concern in marine

mammals, but judging by current research, they

generally are much less important toxicologically

than the first group of compounds and their metabolites.

PCBs and DDTs are the classes of persistent

bioaccumulating toxic compounds of most concern

to marine mammals (reviewed by O’Shea 1999).

PCBs have a potentially broad range of toxic effects

(Safe 1984, 1994). These include effects on immune, endocrine, and nervous system function,
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

78

resulting in interference with growth, development,

sexual differentiation, behavior, and resistance to

disease. In addition to the PCBs themselves, two

classes of metabolites, (methylsulfone-PCBs and

hydroxy-PCBs) have been shown to be persistent

and potentially toxic. Methylsulfone-PCBs accumulate selectively in tissues such as lung and liver

in some mammals, but this is very species-specific.

Their concentration is typically on the order of 3 to

5% of total PCBs in marine mammals. Some

methylsulfone-PCBs are potent cytochrome P450

enzyme inducers. They have been found to decrease pup survival and reduce thyroxine levels in

blood of mink dosed with a mixture similar to that

found in Baltic seals. However, their toxicity is not

well understood. Hydroxy-PCBs have a structure

very similar to that of thyroxine, and they have been

shown to bind competitively to the thyroxine transport protein, TTR. This results in lowered circulating levels of thyroxine and vitamin A. The consequences of this are unknown. Hydroxy-PCBs have

been found at concentrations similar to those of the

PCBs themselves in the plasma of humans, polar

bears, and experimental laboratory mammals, but as

yet there are no data for their occurrence in marine

mammals other than the polar bear. Members of the

DDT family and metabolites have well-documented

effects on endocrine systems, especially corticostero

id synthesis in the adrenal gland. The compound

o,p’-DDD was even used to treat Cushing’s disease,

an adrenal dysfunction in humans (Gutierrez and

Crooke 1980). A methylsulfone metabolite of DDE

is a potent adrenocortolytic agent in mice and mink,

but there appear to be large species differences.

Long-term trends of PCBs and DDTs in the

environment must be understood in a global context.

Although both groups of compounds have been

controlled in the major industrialized countries of

the world for more than 20 years, this should not

lead us to believe that the problems have gone

away. DDT continues to be manufactured and used

in large amounts in some tropical countries (Anonymous 1996). It is likely that PCBs continue to be

manufactured in the former Soviet Union. An

enormous inventory of PCBs is still in use in electrical equipment around the world or is improperly

stored in waste dumps. PCB emissions to the

atmosphere from large urban areas with no particularly identifiable source are probably large. Land

and water surfaces all over the world function as

temporary sinks for quantities of these compounds,

effectively retaining and recycling them back into

the oceans, via the atmosphere, for decades. The

upper levels of ocean sediments also serve as an

important reservoir for PCBs, which then can return

to the food chain when ingested by benthic organisms. Rates of PCB destruction in the environment

appear to be extremely low. Therefore, environmental decreases are mainly due to effective removal from recycling by physical processes such as

burial in sediments or redistribution. 

The voluntary ban on sale of PCBs for open uses

in the United States in the early 1970s had an almost

immediate effect on PCB levels in the environment

close to highly industrial urban areas. Exponential

rates of decline at half-lives on the order of three to

five years were recorded throughout the 1970s in

biota from the Great Lakes, nearshore marine

environments of North America, and the Baltic Sea

(Addison et al. 1986, Blomkvist et al. 1992, Falandysz 1994, De Vault et al. 1996). However, these

rates began to slow in the 1980s, and in the 1990s

levels are no longer declining at statistically meaningful rates (Beck et al. 1994, Tanabe et al. 1994a,

De Vault et al. 1996, Muir et al. 1996). Marine

environments remote from sources were never as

highly contaminated as those close to sources.

However, the effects of production controls have

been limited by the fact that loading to the global

marine system is governed largely by long-range

physical transport by air and water and globalequilibration processes, and not by proximity to

sources (Tanabe et al. 1983, 1994b, Simonich and

Hites 1995). This dampening effect explains why

there have been timelags of five or more years for

peak organochlorine concentrations to occur in

remote environments (e.g., the 1976 peak in the

northern fur seal [Tanabe et al. 1994a]). The peak

may have occurred even later in the Arctic, which is

isolated from mid-latitude atmospheric circulation

in summer. For example, concentrations of PCBs in

polar bears from Hudson Bay were higher in 1984
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

79

than they were in 1969 or 1992 (Norstrom et al.

1998). Rates of decline subsequent to the peak were

also much slower than at mid-latitudes.

The situation for DDT is less clear, possibly

because of the continuing influx to the environment

from Asia. Dramatic declines occurred in the 1970s

in the marine environment close to areas of use in

the United States and Canada, and also in the Baltic

Sea. Similar to PCBs, declines in DDT in remote

environments were less dramatic in the 1970s.

However, declines may be continuing in some

remote areas. This regional behavior may be driven

by the large source to the atmosphere from Asia,

which would not be expected to influence all areas

in the Northern Hemisphere equally. 

The “cold condensation effect” has gained

prominence in describing transport processes to

polar environments (Wania and Mackay 1996).

This effect is driven by the fact that some persistent

compounds are more soluble in cold than warm

water. It has been elegantly demonstrated for

HCHs. Recent evidence shows that “old” water

under the north polar ice cap is out of equilibrium

with air over the ice, and it outgasses when it reach

es open water, becoming a net source to the atmosphere (Jantunen and Bidleman 1995, Hargrave et

al. 1997). This reverse of the cold condensation

effect demonstrates the point that thermodynamic

equilibration processes are the driving force in

planetary distribution of some contaminants. It

would be a mistake to believe that the cold condensation effect simply moves organochlorines from

warm to cold environments. There is no evidence

that the net movement from warm to cold environments is occurring at a perceptible rate for the less

volatile and less water-soluble contaminants such as

PCBs and DDT. Concentrations of these compounds have remained consistently lower in the

water and the biota of the Arctic than in those of

mid-latitudes over the past ten years (Muir et al.

1992, Iwata et al. 1993, Norstrom and Muir 1994).

Atmospheric circulation within the temperate

zones of the Northern and Southern Hemispheres is

much more rapid than exchange between the hemispheres because the tropics constitute a barrier to air

exchange. The long-term prospect of net movement

of persistent organochlorine chemicals from the

Northern to the Southern Hemisphere therefore

must be considered. Such movement may explain

PCB trends in minke whales. Northern minke

whales have much higher levels of PCBs than

southern minke whales (Tanabe, pers. comm.).

While there are no significant temporal trends in

recent PCB concentrations in the northern population, there are indications of an increase in PCBs in

the southern minke whale population.

The shift to a more nearly global steady-state

concentration is likely the dominant process in the

long-term trends of PCBs and DDTs in the marine

environment. We can expect future rates of change

to be slow, based on the history of the last decade.

The rate of decline depends to some extent on

whether the present concentrations are being maintained by sources that can be controlled by destroying inventory and preventing further manufacture

and use. However, it is possible that recycling of

historically emitted PCBs and DDT is the major

factor in maintenance of present environmental

concentrations.

Future Needs to Improve and Ensure Consistency of Sample Collection and Analysis

Sample Collection (and Storage). The development of a universal protocol for sample collection

that includes all basic (Level A) data and supporting

documentation (Geraci and Lounsbury 1993) should

be encouraged. We emphasize the value of using

animals from fishery bycatch, hunting, live-capture

operations, and fresh strandings, and samples

collected by biopsy darting. It is important to note

that samples from stranded animals that may be

suffering from disease and have poor nutritional

status may not be representative of healthy animals.

We encourage further development of biopsy

techniques to overcome the limitations of small

sample sizes, the lack of associated life history

information, and the questionable comparability

between biopsy samples and underlying blubber

samples. We recognize the need to investigate

storage stability of contaminants and tissues and to

develop appropriate recommendations.
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Sample Analysis, Data Reporting, and Archiving.

As analytical techniques are developed, data comparability among laboratories should be assured on a

global scale. We recommend that laboratories adopt

a performance-based quality-assurance program that

incorporates standard reference materials (SRMs)

and participation in intercomparison exercises in

their protocols. SRMs should be developed for

emerging chemicals, and existing SRMs should be

analyzed and certified for these emerging classes of

chemicals.

We recommend that chemical analyses of

marine mammal tissues generate quantitative data

on as large a number of compounds as possible.

This will provide robust data sets for future use.

We encourage the development of protocols stipulating quantitation of a minimum number of compounds of persistent contaminants, such as PCBs, in

order to enhance the comparability of data sets for

purposes of risk determination and trend analysis.

We recognize that in some instances (e.g., damage

assessment, risk assessment, or environmental

emergencies such as oil spills) a smaller number of

analyses may be appropriate (e.g., screening analyses) as long as the quality assurance (e.g., SRMs)

supports the data. 

Concerns Regarding Developing Nations

Many of the contaminants that are of concern in

relation to marine mammal populations have been

banned in industrialized countries. Their continued

use in and export from developing nations represents a risk to marine mammal populations. For

example, India still produces 4,000 metric tons of

DDT per year (Anonymous 1996). The use of

PCBs continues in the former Soviet Union, although decisions to terminate their manufacture

may have been reached very recently in the Russian

Federation or in one or more of the newly independent republics. In general, there is a lack of information on production and use of POPs in developing

nations. 

As a step toward understanding the distribution

of POPs in the Southern Ocean, we strongly recommend that contaminant studies be incorporated into

ongoing life history investigations of marine mammals. Emphasis should be on species and populations that can be considered sentinels or indicators

of regional contaminant burdens. We recommend

that multidisciplinary studies be conducted on

“sentinel” marine mammal populations and that

these studies include investigations of contaminants,

life history, biomarkers, and animal health. We

encourage institutions and agencies to work together

in this regard.

Future Monitoring and Research Needs

Emissions. Most monitoring studies have been

preoccupied with water and tissue analyses rather

than with collecting data on global use and release

of persistent chemicals. More effort should be

devoted to identifying emission sources and calculating environmental loads. This information is

crucial to the interpretation of monitoring data and

to understanding the spatial and temporal distribution of chemicals in biota. Such information should

be available through various programs including the

OECD, UNEP, and International Program on

Chemical Safety (IPCS). 

Contaminant Levels in Marine Mammals. The

study of individuals has been and will remain

essential for understanding animal health in relation

to contaminants. However, to understand effects on

marine mammal populations, information on individual animal health must be supplemented with

information on habitat quality, life history, and

trophic relationships. Population studies will

require multidisciplinary collaborative efforts

among government, academic, and non-government

organizations. Specific research and monitoring

goals and needs should include the following:

C Species should be sampled in both nearshore

and pelagic environments, following suitable

protocols. Such species might include ringed

seals, fur seals, striped dolphins, bottlenose

dolphins, bowhead whales, minke whales, and

beluga whales.

C Monitoring of marine mammal populations that

are recovering, stable, and declining is ex

tremely valuable and should continue. Recovering populations provide reference values for

effect thresholds, and these may constitute the
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81

only measures of the consequences of contamination.

C Archiving of tissue specimens in dependable,

long-term programs is essential. Retrospective

analysis depends on specimen banking; thus

support for tissue archiving must also be dependable and long-term. Samples used for

estimating temporal trends should be collected

and maintained in a way that maximizes the

number of contaminants that are measurable by

the best available techniques. Sampling protocols ideally would include blubber, liver, and

plasma/serum. As these samples are analyzed,

researchers should explore for the widest possible array of compounds with properties that may

fall outside the realm of those currently examined (e.g., hydroxy and methylsulfone PCBs).

C Collecting, analyzing, and archiving samples for

biomarker determinations.

C Developing and refining food-chain models to

(1) assess and validate the exposure of mammals

to a limited number of well-known chemicals;

and (2) select new priority chemicals on the

basis of emission, physico-chemical, and toxicological data.

C Monitoring of marine mammal tissues for wellknown contaminants such as PCBs and DDTs

should continue. Such information is crucial to

understanding processes related to the fate,

behavior, and population-level effects of these

chemicals. Furthermore, data on these “old”

compounds will be crucial for validating models

developed for the assessment of risks associated

with new contaminants.

C Contaminant concentrations in tissue samples

should be interpreted in the context of animal

ecology and habitat quality. We encourage the

use of existing data and the development of new

data sets on the levels of contaminants in prey.

Such data will facilitate interpretation of trends

in current contaminants and estimation of exposure to compounds not yet identified. It is also

important to encourage the integration of all

monitoring studies with hypothesis-driven

research.

C Efforts to examine the global fate and transport

of persistent organic contaminants should be

supported. In this regard, we recognize that

there is a large data gap in the Southern Hemisphere. As discussed earlier in this report, levels

of HCHs are high in the Arctic due to the physical properties of this group of compounds.

Also, the production of PCBs in the former

Soviet Union has global implications.

C Much more research is needed before we can

interpret the relationships between measured

contaminant concentrations and measured

biological effects in marine mammals. Studies

must include laboratory experiments on appropriate animal models and surrogate species, riskassessment modeling, and controlled experimental work with marine mammals that is designed

to address critical research questions, applies

sound scientific criteria, and has statistical

validity.

Future Management Needs

Provide Contaminant Information in More

Easily Understood Formats. Information needs to

be developed in the form of interpreted data sets that

are useable by policy makers, environmental managers, and the general public, preferably in a GIS

format. Programs are needed to heighten awareness

and to inform the public and policy makers of the

significance of contaminants in marine mammals,

including “old” contaminants such as DDT and

PCBs that are still found in the environment.

Among the tools available for this purpose are the

mainstream media, web pages, the Internet, and

liaisons with government agencies and international

non-government organizations, e.g., World Wide

Fund for Nature (WWF), International Union for the

Conservation of Nature and Natural Resources

(IUCN–World Conservation Union), and Center for

Marine Conservation.

Develop Stable Funding Support. Stable funding

is essential for these long-term research and monitoring efforts. For example, there is recognized

value in the continued monitoring of contaminants

in marine mammal populations that are at equilibrium or recovering. An easier mechanism must be

developed to facilitate the transfer of funds among
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

82

federal and state agencies and non-government

organizations. New funding opportunities such as

partnerships with industries, foundations, and other

benefactors should be identified.

Convene Expert Panels Periodically. An international group of experts should be convened on a

periodic basis to review and interpret contaminant

data on marine mammals. The output of such

meetings would be a status report, including databases and comparisons.

Increase Information Transfer. It is necessary

that the Marine Mammal Commission and other

responsible agencies facilitate a dialog among

federal agencies and international agencies such as

the OECD, IPCS, and UNEP. These organizations

should be able to provide basic information on the

production, use, physico-chemical properties,

toxicology, and ecological effects of anthropogenic

chemicals in the environment. Such information is

crucial for anticipating future problems associated

with chemical contaminants in the marine environment.

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84

Section IV. EXTENDED ABSTRACTS

OF PLENARY PRESENTATIONS

Persistent Ocean Contaminants and Marine Mammals: 

A Retrospective Overview

Thomas J. O’Shea

U.S. Geological Survey

Midcontinent Ecological Science Center

4512 McMurry Ave., Fort Collins, CO 80525–3400

Shinsuke Tanabe 

Department of Environment Conservation

Ehime University

Tarumi 3-5-7, Matsuyama 790, Japan

Introduction

In this paper we present (1) a chronological summary of knowledge about marine mammals and

persistent ocean contaminants, beginning with the

1940s; (2) a summary of major findings and advances for each decade in the context of larger

events in the related fields of environmental policy,

toxicology, and technology; (3) indices of the

cumulative amount of information on contaminants

and marine mammals reached each decade based on

compilations of information appearing in about 420

publications in the scientific literature (exclusive of

studies of oil) as documented by O’Shea (1999);

and (4) examples of progress made in the application of the scientific method to problems in the

study of contaminants and marine mammals. The

amount of available information on the topic is

growing at a very rapid pace, but much of this

information is not well integrated. Increasing

applications of sophisticated technology reveal

traces of greater numbers of contaminants, as well

as an escalating multitude of stressors on the marine

environment. In combination, these revelations

make interpretation of observed effects and predictions of future effects of contaminants on marine

mammals an extremely complex task. 

The 1940s and 1950s

During this period, much of the world was involved

in and recovering from massive military conflicts.

Experience in mobilizing technology to serve these

conflicts was followed by great faith in the applications of research in chemistry and physics to further

global social and natural resource development.

Production of PCBs escalated markedly after World

War II, and the era of large-scale use of organochlorine pesticides was also ushered in during this

period. A Nobel Prize was awarded in 1948 for

discovery of the insecticidal properties of DDT, a

compound which saved millions of people from

death due to insect-borne pathogens, but which was

to be found in the blubber of marine mammals in

remote reaches of the world beginning nearly 20

years later; DDT subsequently has become one of

the most intensively studied persistent contaminants. With the exception of radionuclide fallout

from the use and testing of nuclear weapons, there

was little recognition or concern about environmental contaminants during this period, particularly

with regard to marine mammals. The scientific

literature of the time contains no information on

contaminants in marine mammals, although retrospective studies of commercial oils show that seals

and whales contained metabolites of DDT in the

1950s (Addison et al. 1972) and that mercury was

present at low levels in Southern Ocean fin whales
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

85

in the 1940s (Nagakura et al. 1974).

 

The 1960s

This decade witnessed an awakening of concern

about the impacts of persistent environmental

contaminants on human health as well as on wildlife

and ecosystems. In Japan, local effects on human

health from contamination of seafoods with mercury

and rice with PCB oils provided prime examples

that attracted worldwide attention. In 1966, the first

two publications on contaminants in marine mammals reported DDT and metabolites in Antarctic

seals (Sladen et al. 1966, George and Frear 1966),

providing the first published documentation of what

has become a major, long-lasting issue studied

throughout the oceans of the world. By the end of

the decade the presence of mercury, DDT, DDE,

DDD, dieldrin, and PCBs in tissues of marine

mammals had been documented, with published

organochlorine data based on about 50 individual

pinnipeds belonging to six species, four harbor

porpoises, and one common dolphin. Mercury was

the only toxic element reported in marine mammals

in the 1960s, based on examination of 32 ringed

seals from Finland. 

The 1970s

Observational data on the presence of contaminants

in tissues of marine mammals began to expand

rapidly in the 1970s, a time of much formal recognition of the dangers of chemical contamination, as

reflected by worldwide advances in environmental

legislation and policy. These included a number of

formal restrictions on production and use of PCBs

and certain organochlorine pesticides in some parts

of the world. The number of potentially toxic

elements reported in pinniped tissues expanded to

18, and data on elements were reported for at least

1,410 individual marine mammals, including 10

species of pinnipeds and 17 species of cetaceans.

Organochlorines were reported for 1,230 marine

mammals, including 11 species of pinnipeds and 26

species of cetaceans. The list of organochlorines

reported in marine mammals expanded to about 26

compounds or groups of compounds over the course

of the 1970s. Organochlorine residue studies began

to show patterns of accumulation with sex and age,

geographic trends, and “hot spots.” Characteristic

statistical distributions placed most values in the

low to moderate range, with a few more heavily

contaminated individuals. A few attempts at experimentation were made in very limited studies of

metals in seals. Some in vitro experiments were

conducted with pinnipeds; these could be classified

as early “biomarker” studies. The first observations

suggesting associations between organochlorines

and reproductive problems in female pinnipeds were

published. These were made on seals in the Baltic

(e.g., Helle 1976a,b) and on California sea lions

(DeLong et al. 1973). However, cause-and-effect

interpretations of these observations were not

possible. Despite advances in other areas of marine

toxicology, no dose-response relationships had been

established for marine mammals, nor had any

experimental tests of hypotheses been conducted.

The 1980s

This decade was marked by (1) ever-expanding

information on chemical residues in the bodies

(primarily blubber) of marine mammals; (2) landmark experimental approaches with captive pinnipeds; (3) more sophisticated analytical technologies

allowing quantification of individual PCB congeners and corresponding hypotheses about metabolic

capacities of marine mammals, and the possible

vulnerability of their endocrine physiology; and (4)

application of biomarkers to the study of contaminants in marine mammals. In the first full toxicological experiment with marine mammals, Reijnders

(1986) showed that reproduction in captive female

harbor seals was impaired when the diet consisted

of fish with higher concentrations of mixed organochlorines. Tanabe (1988), Tanabe et al. (e.g., 1987,

1988), and Boon et al. (e.g., 1987, 1992) showed

that certain PCB congeners were especially recalcitrant to metabolism in marine mammals (based on

comparison of residue profiles in marine mammals

with those in their food and those in terrestrial

mammals). These studies suggested that this recalcitrance was linked with mixed-function oxidase

systems and possible endocrinological effects. The
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

86

hypothesis that organochlorines interfere with

adrenocortical metabolism was established based on

pathology in seals (Bergman and Olsson 1985).

Biomarker studies were initiated primarily in the

latter half of this decade, with biomarker information of some kind available for at least 83 individuals in eight species of cetaceans and 90 individuals

in five species of pinnipeds (Fossi and Marsili

1997). Much residue data accrued in the 1980s, and

many more extensive studies verified strong patterns of accumulation for some organochlorine

compounds by sex and age across species: concentrations in blubber increase with age in males but

reach a plateau or decline after the age of first

reproduction in females. This is because females

transfer compounds to young, primarily via lactation. Observational data on contaminant residues

continued to overshadow experimental investigations, with organochlorine analyses embracing

another 2700 individuals (in 12 pinniped species, 33

cetacean species, and other groups); toxic element

determinations were carried out on the tissues of

more than 1,700 individual marine mammals.

 

The 1990s

Deepening concern and debate about the influence

of contaminants on disease processes have come to

the forefront in the present decade. An additional

focus has been on the possible importance of endocrine disruptors to population dynamics. Studies of

beluga whales in the St. Lawrence River system

(e.g., Béland et al. 1993, Martineau et al. 1994) and

pinnipeds in the Baltic (e.g., Bergman et al. 1992)

showed various pathologies strongly suggestive of

contaminant impacts. Die-offs of bottlenose dolphins on the Atlantic coast of the United States in

the late 1980s (e.g., Geraci 1989, Lipscomb et al.

1994, Duignan et al. 1996) were followed by additional dramatic events involving pinnipeds and

small cetaceans in Europe and the Gulf of Mexico

during the 1990s (e.g., Domingo et al. 1990, Aguilar

and Borrell 1994, Lipscomb et al. 1996,

Taubenberger et al. 1996). Studies of these events

included designs that statistically partitioned cause

of death and organochlorine residue data among

variables such as age and sex to test hypotheses

about linkages between disease and contaminants,

with sometimes conflicting results (e.g., Hall et al.

1992, Aguilar and Borrell 1994). Die-offs associated with morbillivirus infections were very dramatic and attracted much attention and speculation

about links with contaminants, but such infections

are typically associated with high mortality in naive

mammalian populations even when contaminants

are not present. Concern about disease-organochlorine relationships prompted some additional

rare examples of experimental approaches using

captive harbor seals. These studies showed

organochlorine-linked effects on immunocompeten

ce (e.g., Ross et al. 1995, 1996, Harder et al. 1992,

De Swart et al. 1996). Biomarker studies continued

to increase in the 1990s, with some form of sampling published for at least 181 cetaceans in seven

species and 384 pinnipeds in nine species.

Biomarker studies began to include organochlorine

determinations from biopsies or tissue samples from

the same individuals, and results generally showed

a correspondence with mixed function oxidase

activity. Other observation-level data continue to

accumulate during the present decade, with

analytical chemistry techniques greatly expanding

the numbers of individual compounds (especially

industrial chemical congeners) and elements

reported in marine mammal tissues at ever finer

levels of sensitivity. Butyltins in tissues of marine

mammals were first reported in the 1990s and are

becoming commonly reported (e.g., Kannan et al.

1998, Tanabe et al. 1998), but they are of uncertain

toxicological significance to these species. Some 50

toxic elements have been found in marine mammals

thus far in the 1990s, based on assays from at least

5,556 individuals. Publications document that

more than 5,529 individuals have also been

examined for organochlorines in the 1990s,

including 17 species of pinnipeds, 40 species of

cetaceans, polar bears, sea otters, and manatees.

Comparisons of recent data with patterns from past

decades have been made, but temporal trends are

uneven among species, regions, and specific

contaminants. Despite the existence of an enormous

database on contaminant residues (contaminant data

are now reported for more than 18,000 individuals),

it has not been firmly established what
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

87

concentrations of any particular substance in

blubber are diagnostic of detrimental health effects

in marine mammals. The database itself is strongly

biased, with a huge proportion of the samples taken

from the Northern Hemisphere, particularly

Canadian and European waters. The data are also

biased by species: 77% of the individual pinnipeds

examined for organochlorines and 73% of those

examined for toxic elements are from just four

species; 67% of all cetaceans examined for

organochlorines and 64% of those sampled for toxic

elements have been from only five species. Few

data exist for other contaminants in marine

mammals, such as radionuclides or PAH’s, but

surveys conducted thus far do not suggest

significant problems. Attempts to predict future

impacts of known and possibly “new” contaminants

on marine mammal species and populations are

exacerbated by the many other changes in the

marine environment. Confounding factors can

include harvesting and bycatch (including historical

impacts), depletion of fisheries and other food

chain shifts, eutrophication in nearshore

environments, global temperature flux,

introductions of exotic species, ship traffic, noise

pollution, and toxic algal blooms.

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WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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Reproductive and Developmental Effects of Endocrine-Disrupting Chemicals

on Marine Mammals

Peter J. H. Reijnders 

Institute for Forestry and Nature Research

Department of Ecosystem Health

P.O. Box 167, 1790 AD Den Burg, The Netherlands

Introduction

A large number of xenobiotics with endocrinedisrupting properties have been detected in marine

mammal tissue (Wagemann and Muir 1984, Aguilar

and Borrell 1995, Colborn and Smolen 1996,

Reijnders 1996). Although most of the species

known to be contaminated in this way are coastal,

considerable concentrations of such compounds

have even been detected in at least one cetacean that

forages in deep water, the sperm whale (de Boer et

al. 1998). Only in a few studies have observed

reproductive disorders been found to be associated

with certain chlorinated hydrocarbons and their

metabolites. Among these studies are those

involving ringed and gray seals in the Baltic Sea

(Helle 1980, Bergman and Olsson 1985), beluga

whales in the St. Lawrence River (Béland et al.

1992), harbor seals in the Wadden Sea (Reijnders

1980), and California sea lions in the eastern Pacific

Ocean (DeLong et al. 1973). The findings of these

studies, although strongly suggestive, have not been

conclusive. The etiology of the observed disorder

has usually been uncertain, and proof of a causal

relationship between exposure to a specific

contaminant and an impact on the reproductive or

endocrine system has remained elusive.

This paper discusses the issue from an epidemiological point of view. My focus is on marine

mammal species in which disorders in hormone

concentrations, reproductive problems, or

pathological conditions associated with hormonal

imbalance have been observed. An overview of

associations between organochlorines and marine

mammal reproduction and endocrinology is

presented in Table 10. I conclude with some

comments on the possibilities of monitoring and

evaluating problems related to xenobiotic-induced

reproductive impairment and endocrine disruption

in marine mammals.

Basic Pharmacology and Physiology of

Hormones in Reproduction and Early

Development

Hormones are messenger compounds. Their release

leads to functional changes in an organism’s cells,

tissues, and organs. They are produced by

endocrine organs and delivered into the

bloodstream. A small percentage of hormones

circulate freely, but the majority are bound to

transport proteins. The free hormones diffuse into

the tissues and cells. Target cells possess specific

receptor molecules which bind to particular

hormones, leading to activation of the receptor.

Steroid hormones as well as thyroid hormones play

important roles in reproduction and early

development. They are discussed separately here.

In vertebrates, sex hormones belong to a group

of steroids which are synthesized from cholesterol.

Steroids can be divided into four functional groups:

the three sex hormone groups (androgens, estrogens,

and progesterone) and the glucocorticosteroids. The

latter plays a role in regulating metabolism and

growth and in osmoregulation.

In mammals, steroid hormones are mainly

synthesized in the adrenals, gonads, and placenta.

The production of each of the sex hormones is

localized in a specific gland such as testosterone in

the testes, estrogens and progesterone in the ovaries,

and progesterone, estrogens, and testosterone in the

adrenals. These organs can, in many species, 
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

94

Table 10. Associations between organochlorines and marine mammal reproduction and endocrinology

Where in Process Species Location Mode of Action Certainty ofMode of Action* Contaminants Certainty ofContaminants*

Reproductive Disorders

Implantation

failure1

implantation harbor seal Wadden Sea hormone metabolism

enhancement

 2 PCBs/-metabolites 2

 Failed

implantation or

fetal

development2

implantation beluga whale St. Lawrence River unknown 4 organochlorines 4

Stenosis and

occlusions3

post partum gray and ringed seals Baltic Sea organochlorine induced

uterine pathology

3 PCBs/DDE/MSFs 3

Sterility4 unknown gray and ringed seals Baltic Sea pathologic sterility 1 PCBs/DDT/-

metabolites

3

Premature pupping5

late gestation California sea lion Southern California

Bight microsomal enzyme

induction; steroid

mimicking

3 PCBs/DDT 3

Hormonal Disorders

Low vitamin A

/thyroid hormones6

all ages harbor seal Wadden Sea binding competition 1 PCBs/-metabolites 2

Reduced

testosterone7

adults Dall’s porpoise North Pacific Ocean unknown 4 DDE/possibly PCBs 4

Lowered

estradiol level8 implantation harbor seal Wadden Sea enhanced hydroxylation 3 PCBs/-metabolites 2

Morphological Disorders

Skull lesions

(osteoporosis,

paradentitis)9

predominantly

adults harbor and grayseals

Baltic Sea,

Wadden Sea infection/ hyperadrenocortical

2 PCBs/DDT/-

metabolites

3

Exostosis10 all ages harbor seal Baltic Sea, west coast of Sweden

unknown 4 PCBs/DDT/-

metabolites

3

Testis

abnormalities11

immatures and

adults minke whale Southern Ocean unknown 4 organochlorines 4

Adrenal

hyperplasia12

unknown beluga whale St. Lawrence River unknown 4 organochlorines 4

Hermaphroditism13 fetal beluga whale St. Lawrence River genetic/environmental 4 PCBs/DDT 4

*1= definite, 2 = probable, 3 = possible, 4 = unknown

1

Reijnders et al. 1986, Reijnders, this report; 2Martineau et al. 1994; 3Helle 1980, Helle et al. 1976; 4Bergman and Olsson 1985; 5DeLong et al. 1973; 6Brouwer et al. 1989; 7Subramanian et al.1987; 8

Reijnders, this report; 9Bergman et al. 1992, Stede and Stede 1990; 10Mortensen et al. 1992; 11Fujise et al. 1998; 12Béland et al. 1992; 13De Guise et al. 1994.

also produce small quantities of the other sex

hormones. The specific pathway of biosynthesis in

mammals is in the following order: cholesterol o

pregnenolone o progesterone o androstenedione

o testosterone o estradiol (Fig. 5).

The hypothalamus and pituitary are responsible

in most vertebrates for the regulation of hormone

concentrations and the timing of reproduction and

sexual development. The hypothalamus produces a

peptide, gonadotropic releasing hormone (GnRH),

which stimulates the pituitary to synthesize follicle

stimulating hormone (FSH) and luteinizing hormone

(LH). These hormones regulate the synthesis of

progesterone, estradiol, and testosterone. Through

the production of FSH and LH, the synthesis

(positive and negative feedback) of sex hormones

and gonadal development are regulated.

Thyroid hormones are important in the structural

and functional development of sex organs and the

brain, both intrauterine and postnatal. They are
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

95

synthesized by the thyroid gland under stimulation

through the thyroid stimulating hormone produced

by the pituitary. The form that is most important as

a biological parameter is thyroxine (T4, tetraiodothyroxine). 

 

Disorders in Hormone Concentrations

A negative correlation has been observed between

testosterone levels and tissue concentrations of DDE

and possibly PCBs in Dall’s porpoises (Subramanian et al. 1987). In a semi-field experiment

with harbor seals, Reijnders (1986, 1990) found that

lower levels of 17ß-estradiol occurred around the

time of implantation. A possible explanation for the

observed lower hormone levels in both Dall’s

porpoises and harbor seals would be an increased

breakdown of steroids as a consequence of PCB- or

PCB metabolite-induced enzyme activity.

Enhanced steroidogenesis caused by some metals

and a PCB mixture (Arochlor 1254) has been

demonstrated in vitro for gray seals (Freeman and

Sangalang 1977). Furthermore, increased

metabolism of PCBs as a result of P450-enzyme

induction has already been demonstrated in marine

mammals (Tanabe et al. 1988, Boon et al. 1992). A

second explanation might be that PCB and DDE, or

metabolites thereof, bind to hormone carrier

proteins and/or hormone receptors. If such binding

were to occur, either tissue metabolism of steroids

would be hindered or binding of steroids to receptor

proteins in target tissue would be impeded. It is

conceivable that both mechanisms — increased

steroid breakdown and the binding of xenobiotic

compounds to carrier proteins or hormone receptors

— could operate in tandem.

Figure 5. Major steroidogenic pathways in mammalian endocrine tissues. Black arrows indicate P450-

mediated conversions.

With respect to the first mechanism, Troisi and

Mason (1998) found experimentally that rates of

progesterone and testosterone metabolism in harbor

seals were negatively correlated with both PCB

concentrations and the level of P450-enzyme

induction. Applying the findings by Troisi and
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

96

Mason (1998) to Dall’s porpoise, the lowered levels

of testosterone reported by Subramanian et al.

(1987) could be explained by a hindrance in the

transformation of precursors for testosterone by

PCB or DDE metabolites. This postulated

explanation obviously needs further testing.

Concerning the second mechanism, it is known

that PCB metabolites, in particular PCB-methyl

sulfones, bind to uteroglobin (Patnode and Curtis

1994). Since we did not find any receptor

interference in in vitro pilot experiments with harbor

seal blood, this mechanism is not considered a likely

explanation for the observed reproductive failure in

this species. The finding by Troisi and Mason

(1998) of decreasing metabolism of progesterone

and testosterone in liver microsomes does not allow

a conclusion about a possible impediment of the

transformation of progesterone and testosterone,

that might in turn have led to the lower estradiol

levels observed in harbor seals. This is because

those transformations occur in the reproductive

organs. However, it has been found by Funae and

Imaoka (1993) that sex-dependent cytochrome P450 isoenzyme patterns exist. It is known that

induction of CYP1A(2) causes increased

hydroxylation of estradiol, leading to enhanced

excretion and hence lower levels of estradiol. It has

been demonstrated that induction of CYP1A is

significant in harbor seals (Boon et al. 1987). I

postulate that enhanced breakdown of estradiol,

through enzyme-induced metabolism by

organochlorines, is a plausible mode of action to

explain the lower levels of estradiol observed in

harbor seals. Estradiol has a priming effect on the

proliferation of the endometrium, in effect

preceding proliferation of the luminal and glandular

epithelium under the influence of progesterone. The

lower levels of estradiol could have impaired

endometrial receptivity and prevented successful

implantation of the blastocyst. Further studies are

planned to investigate this possibility.

Decreased levels of thyroid hormones have been

found in harbor seals (Brouwer et al. 1989) as a

consequence of competition between a hydroxylated

metabolite of PCB-77 and thyroid hormones for

binding to a transport protein, transthyretin (TTR).

Such a hypothyroid condition can have significant

effects on early development and later reproductive

performance. Fetal accumulation of hydroxylated

PCB-metabolites has been found to occur in

experimental animals and may also occur in seals

(Brouwer et al. 1998). Given that thyroids are

involved in the development of Sertoli and Leydig

cells (spermatogenesis), brain development, and

early development of the sex organs, further

research in this area is warranted.

Green et al. (1996) and Green (1997) provide

additional information on lactational transfer of

PCB-methyl sulfones (PCB-MSFs) from gray seals

to their offspring. They report that the summed

concentrations of PCB-MSFs (in lipid) are

approximately 5% of the total PCB concentration.

A similar ratio was found in seal milk. The uptake

of PCB-MSFs is therefore quantitatively important.

Moreover, the pups excrete only approximately

0.5% from the amount they ingest. In contrast to

the mobilization of PCB-congeners from maternal

blubber to milk, which is negatively correlated with

congener-lipophilicity, the metabolization of PCBMSFs is independent from the degree of

chlorination as well as the chlorination pattern. The

ratio PCB-MSFs/total PCBs is therefore higher in

milk than in blubber. This metabolization process,

offering a certain protection against the more

lipophilic PCBs, obviously does not work in the

case of the PCB-MSFs. The significance of this

finding remains unclear.

Reproductive Disorders

Clear cases of hermaphroditism were observed in

about two out of 120 examined beluga whales in the

St. Lawrence River (De Guise et al. 1994, P.

Béland, pers. comm.). This condition has been

attributed to hormonal disturbance in early

pregnancy, whereby normal differentiation of male

and female organs was disrupted. Research is

ongoing to test that hypothesis and to acquire

information on the underlying mechanism.

In examined mature female Baltic seals, 30% of

the gray and 70% of the ringed seals exhibited

partial or complete sterility, caused by stenosis and
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

97

occlusions. Recent studies suggest that PCB- and

DDE-methyl sulfones are the toxic compounds

responsible for these abnormalities (Olsson et al.

1994). A plausible hypothesis is that early

pregnancy is interrupted, perhaps via decreased

uteroglobin binding due to the methyl sulfoneoccupation or low hormone levels, followed by

development of pathological disorders. Toxic

effects in several steps in the brain-hypothalamichypophyseal-adrenal-placental axis could be

involved in the latter stage (Reijnders and Brasseur

1992). Further investigations are needed to

elucidate this phenomenon. DeLong et al. (1973)

found premature pupping in California sea lions to

be associated with high PCB and DDE levels. The

concurrent finding in the animals of pathogens with

known potential to interfere with pregnancy

rendered it impossible to attribute causation

specifically to either of the organochlorines.

Abnormal testes — transformation of

epididymal and testicular tissue — have been

observed in North Pacific minke whales (Fujise et

al. 1998). A possible relationship with levels of

organochlorines has been postulated. Further

histological examinations and pathology

assessments are being conducted to investigate this

phenomenon.

Other Hormone-Related Disorders

Besides sterility, a suite of pathologies and disorders

have been observed in Baltic seals. These include

exostosis in harbor seal skulls (Mortensen et al.

1992) and osteoporosis in gray seal skulls (Olsson

et al. 1994). Similar disorders have been found in

harbor seals in the Wadden Sea (Stede and Stede

1990). This disease complex is characterized as

hyperadrenocorticism. It is unclear whether

hyperadrenocorticism is manifested in early

development.

The research field between reproductive biology

and immunology is in an early stage of

development. It is known that both the humoral

(antibodies) and cellular (lymphocytes) aspects of

the immune system are regulated by estrogens and

androgens (Grossman 1985). Disruption in steroid

hormone balance might therefore lead to

malfunctioning of the immune system. Of relevance

in the present context is the role of progesterone and

estradiol in preventing the maternal-fetal rejection

response. This relationship could help explain the

observed problems of harbor seals in the Wadden

Sea as these problems occurred at around the time

of implantation. Also, corticosteroids (Wilckens

and de Rijk 1997) and thyroid hormones (Brouwer

et al. 1989, 1998) are involved in immune

functioning. The possible effects of xenobioticcaused thyroid and corticosteroid hormone

imbalances on early development and reproduction

are insufficiently known.

Monitoring and Evaluation of Effects and

Related Research Needs

There are serious impediments to monitoring and

evaluating hormone-related xenobiotic effects.

Firstly, the majority of the present tests do not

measure transgenerational influence, yet several

disorders occur only in the adult stage or offspring.

Secondly, gene expression is affected, not gene

constitution. Therefore, mutagenicity endpoint tests

are not particularly relevant. Thirdly, many tests are

in vitro, and this complicates investigations of

disruption in neurobehavioral function and

reproductive morphological development. Finally,

some xeno-estrogens only become biologically

active after in vivo metabolism (e.g., methoxychlor).

Development of hormone-responsive cell

cultures as biomarkers could provide a partial

solution (see Colborn et al. 1993). Biomarkers are

available to measure exposure to xenobiotics,

including xeno-estrogens (Fossi 1994). A series of

recent studies describe techniques to investigate

metabolism of PCBs, PCDDs, PCDFs, and toxaphenes in marine mammals (Troisi and Mason 1997,

Boon et al. 1997, 1998, Letcher et al. 1998). These

provide opportunities to measure exposure of

marine mammals to, for example, xeno-estrogens

and other endocrine-disrupting contaminants.

However, preparatory research has to be carried out

to adapt existing biomarker protocols for use in

marine mammal studies. This includes sampling
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

98

tissue, particularly of neonatal and juvenile animals,

to analyze for (1) thyroid hormones and vitamin A

(important in cell differentiation) in blood and

brain; (2) thyroid hormones and vitamin A in brain

and liver; (3) estrogen-receptor binding capacity of

ovarian, brain, and liver tissue; (4) glial fibrillary

acidic protein and synaptophysins in brain; (5)

P450-enzyme induction (i.e., CYP-1A) in liver,

brain, and uterus; and (6) levels of xeno-estrogens

in blubber, blood, liver, and brain.

To enhance evaluation of the results, in terms of

biological significance, it is important to carry out

investigations and compare trends in animals from

relatively unpolluted as well as highly polluted

areas. Initially, a choice has to be made for model

compounds as well as for model species occurring

over a gradient of pollution. Studies in relatively

clean areas serve mainly to obtain reference values

for exposure to contaminants and indicators for the

status (functioning) of the studied population.

Studies in highly polluted areas make it possible to

carry out research on pathology in neonatal and

juvenile animals. In combination with analyses for

contaminants and associated physiological and

pathological responses, these studies will facilitate

development of a multiple response concept as

described by Reijnders (1994) and Reijnders and de

Ruiter-Dijkman (1995). The development of

techniques to extrapolate observed individual

responses, and thereby evaluate population-level

and possibly ecosystem-level effects, is equally

important.

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Amsterdam.

Stede, G., and M. Stede. 1990. Orientierende Untersuchungen von Seehundschädeln auf pathalogische

Knochenveränderungen. Pages 31–53 in Zoologische

und Ethologische Untersuchungen zum Robbensterben. Inst. f. Haustierkunde, Kiel, Germany.

Subramanian, A. N., S. Tanabe, R. Tatsukawa, S. Saito,

and N. Miyazaki. 1987. Reductions in the

testosterone levels by PCBs and DDE in Dall’s

porpoises of northwestern North Pacific. Marine

Pollution Bulletin 18:643–646.

Tanabe, S., S. Watanabe, H. Kan, and R. Tatsukawa.

1988. Capacity and mode of PCB metabolism in

small cetaceans. Marine Mammal Science 4:103–

124.

Troisi, G. M., and C. F. Mason. 1997. Cytochromes

P450, P420 and mixed-function oxidases as biomarkers of polychlorinated biphenyl (PCB) exposure

in harbour seals (Phoca vitulina). Chemosphere

35:1933–1946.

Troisi, G. M., and C. F. Mason. 1998. Steroid hormone

metabolism in harbour seals (Phoca vitulina) exposed

to polychlorinated biphenyls (PCBs). Marine

Environmental Research. In press.

Wagemann, R., and D. G. C. Muir. 1984.

Concentrations of heavy metals and organochlorines

in marine mammals of northern waters: overview and

evaluation. Canadian Technical Report of Fisheries

and Aquatic Sciences No. 1297. 97 pp.

Wilckens, T., and R. de Rijk. 1997. Glucocorticoids and

immune function: unknown dimensions and new

frontiers. Immunology Today 18:418–424.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

101

Contaminants and Marine Mammal Immunotoxicology and Pathology

Sylvain De Guise

Department of Pathobiology

University of Connecticut

61 North Eagleville Road, U-89

Storrs, CT 06269 

Kimberlee B. Beckmen

Institute of Arctic Biology

University of Alaska Fairbanks

Fairbanks AK 99775

Steven D. Holladay

Virginia Polytechnic Institute

Blacksburg, VA 24061

Recent mass mortality of marine mammals in

different locations, involving a number of different

species, has attracted public attention and prompted

scientific investigations (Geraci et al. 1982, Osterhaus et al. 1988, Kennedy et al. 1991, Domingo et

al. 1990). Consistent findings of relatively high

tissue concentrations of environmental contaminants

have raised questions regarding the role of these

compounds in the development of disease processes.

In particular, there has been concern about the

host’s ability to develop a protective immune

response against pathogens. Contaminant-induced

immunosuppression was proposed as a possible

explanation for the high incidence, diversity, and

severity of lesions caused by opportunistic and

mildly pathogenic bacteria in beluga whales from

the St. Lawrence estuary in Canada (Martineau et

al. 1988, De Guise et al. 1995). Although many

contaminants of the marine environment

(organochlorines, heavy metals, polycyclic aromatic

hydrocarbons) are well characterized as immunotoxicants in laboratory rodents, it is a significant

challenge to demonstrate immunotoxic effects on

marine mammals exposed to these agents. Among

the reasons are that, for marine mammals, (1) the

existing immunologic database is limited, (2) few

assays have been developed and there is limited

availability of reagents with which to evaluate

immune function, (3) most natural populations are

outbred and therefore have considerable genetic

diversity, and (4) logistical and ethical

considerations must be taken into account.

Marine mammal immunology is a relatively

new, rapidly evolving discipline. Its importance has

become more widely appreciated in recent years for

at least two reasons. One is the realization that the

immune system plays a central role in general

health. The other is the realization that immune

function can be influenced by factors such as

pollution or stress. It is important to understand the

complexity of the immune system and its functions,

and to recognize that no single assay can evaluate

the immune system as a whole. Different assays can

evaluate different components, mechanisms, or

functions. Some laboratories have committed

themselves to developing and standardizing assays

and reagents to evaluate particular aspects of the

marine mammal immune system, e.g., humoral, cellmediated, or non-specific immunity. Methods such

as cryopreservation have been validated in order to

standardize the collection and transportation of

samples, regardless of when, where, or from what

population they have been obtained. This facilitates

simultaneous analysis and enhances the possibilities

for making valid comparisons.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

102

Direct determination of the effects of environmental contaminants on the immune system of wild

marine mammals is made difficult by logistical and

ethical considerations. Nevertheless, several

approaches have been used. In vitro exposures of

beluga immune cells to heavy metals and

organochlorines demonstrated the susceptibility of

those cells to toxic compounds at levels comparable

to levels found in the tissues of wild belugas (De

Guise et al. 1996, 1998). When immune cells from

belugas were exposed in vitro to mixtures of

organochlorines, at levels at which the individual

compounds would have had no effect on immune

function, synergistic effects were observed (De

Guise et al. 1998). This observation called attention

to the often overlooked or unsuspected dangers

posed by environmentally relevant complex

mixtures.

Another approach is to use animal models. For

example, the potential immunotoxicity associated

with exposure to complex mixtures of contaminants

has been assessed by feeding one group of rats

highly contaminated blubber from St. Lawrence

belugas and another group much less contaminated

blubber from Arctic or Subarctic belugas (De Guise

et al. unpublished data). Similarly, one can compare

groups of rats fed either oil extracted from highly

contaminated Baltic Sea fish or oil from much less

contaminated Atlantic Ocean fish (Ross et al. 1997).

The in vivo effects of exposure to environmentally

relevant concentrations of pollutants were

demonstrated experimentally in semi-field

conditions where one group of harbor seals was fed

highly contaminated Baltic Sea fish and another

group was fed much less contaminated Atlantic

Ocean fish (De Swart et al. 1994). The animals fed

Baltic Sea fish exhibited impaired natural killer

(NK) cell activity and T-lymphocyte function (de

Swart et al. 1994) as well as delayed-type

hypersensitivity (Ross et al. 1995). These

experimental study designs probably provide the

best means of investigating the effects of exposure

to environmental contaminants through food

consumption. The perinatal transfer of

contaminants (through the placenta and milk) that

occurs in nature, and that affects the highly

vulnerable developing immune system, is not

accounted for, however, in such semi-field

experiments.

Field studies of wild populations of marine

mammals are logistically difficult. However, in a

study of free-ranging bottlenose dolphins in Florida,

decreased lymphocyte proliferation was associated

with increased blood concentrations of

organochlorines (Lahvis et al. 1995). In Alaska,

northern fur seal pups were captured, studied, and

released. Mitogen-induced proliferation of blood

lymphocytes, along with other immunoassays and

health parameters, were evaluated and compared

with whole-blood levels of organochlorines.

Lymphocyte proliferation was negatively correlated

with increasing concentrations of nine PCB

congeners (Beckmen, unpublished data). Moreover,

pups of primiparous dams, having the highest

measured blood levels of organochlorines, had

significantly lower antibody production in response

to vaccination with tetanus toxoid than pups of old

dams, with low blood levels of organochlorines

(Beckmen, unpublished data).

The impact of environmental contaminants on

the health of wild marine mammal populations

cannot be fully understood until the effects of those

contaminants on the immune response have been

properly assessed. Deleterious effects on immune

functions have been observed in marine mammals in

vivo, as well as in animal models and in marine

mammal cells in vitro. Future studies should be

directed toward contaminant exposure at critical life

stages, such as at and near the time of birth, and

effects on the developing immune system.

Identification of a subpopulation or cohort at

greatest risk (highest exposure and critical life

stage) can help focus research and diagnostic efforts

to determine whether adverse health effects are

ongoing or imminent. In addition, studies of the

“normal,” protective marine mammal immune

response to common pathogens should provide a

better understanding of the relationship between a

potentially suppressed immune system and the

development of diseases (possibly including

epizootics).
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

103

References

De Guise, S., D. Martineau, P. Béland, and M. Fournier.

1998. Effects of in vitro exposure of beluga whale

leucocytes to selected organochlorines. Journal of

Toxicology and Environmental Health 55:479–493.

De Guise, S., J. Bernier, D. Martineau, P. Béland, and M.

Fournier. 1996. In vitro exposure of beluga whale

lymphocytes to selected heavy metals.

Environmental Toxicology and Chemistry 15:1357–

1364.

De Guise, S., D. Martineau, P. Béland, and M. Fournier.

1995. Possible mechanisms of action of

environmental contaminants on St. Lawrence beluga

whales (Delphinapterus leucas). Environmental

Health Perspectives 103 (Supplement 4):73–77.

De Swart, R. L., P. S. Ross, L. J. Vedder, H. H. Timmerman, S. H. Heisterkamp, H. van Loveren, J. G. Vos,

P. J. H. Reijnders, and A. D. M .E. Osterhaus. 1994.

Impairment of immune functions in harbour seals

(Phoca vitulina) feeding on fish from polluted waters.

Ambio 23:155–159.

Domingo, M., L. Ferrer, M. Pumarola, A. Marco, J.

Plana, S. Kennedy, and M. McAliskey. 1990.

Morbillivirus in dolphins. Nature 348:21.

Geraci, J. R., D. J. St. Aubin, I. K. Barker, R. G.

Webster, V. S. Hinshaw, W. J. Bean, H. R. Ruhnke,

J. H. Prescott, G. Early, A. S. Baker, S. Madoff, and

R. T. Schooley 1982. Mass mortality of harbor seals:

pneumonia associated with influenza A virus.

Science 215:1129–1131.

Kennedy, S., J. A. Smyth, P. F. Cush, M. McAliskey, S.

J. McCullough, and B. K. Rima. 1991.

Histopathologic and immunocytochemical studies of

distemper in harbor porpoises. Veterinary Pathology

28:1–7.

Lahvis, G. P., R. S. Wells, D. W. Kuehl, J. L. Stewart, H.

L. Rhinehart, and C. S. Via. 1995. Decreased

lymphocyte response in free-ranging bottlenose

dolphins (Tursiops truncatus) are associated with

increased concentrations of PCBs and DDT in

peripheral blood. Environmental Health Perspectives

103 (supplement 6):67–72.

Martineau, D., A. Lagacé, P. Béland, R. Higgins, D.

Armstrong, and L. R. Shugart. 1988. Pathology of

stranded beluga whales (Delphinapterus leucas) from

the St. Lawrence estuary, Québec, Canada. Journal

of Comparative Pathology 98:287–311.

Osterhaus, A. D. M. E., J. Groen, P. De Vries, F. G. C.

M. Uyt de Haag, B. Klingeborn, and R. Zarnke.

1988. Canine distemper virus in seals. Nature

335:403–404.

Ross, P. S., R. L . de Swart, H. van der Vliet, L. Willemsen, A. de Klerk, G. van Amerongen, J. Groen, A.

Brouwer, I. Schipholt, D. C. Morse, H. van Loveren,

A. D. Osterhaus, and J. G. Vos. 1997. Impaired

cellular immune response in rats exposed perinatally

to Baltic Sea herring oil or 2, 3, 7, 8-TCDD.

Archives of Toxicology 71:563–574.

Ross, P. S., R. L. De Swart, P. J. H. Reijnders, H. Van

Loveren, J. G. Vos, and A. D. M. E. Osterhaus.

1995. Contaminant-related suppression of delayedtype hypersensitivity and antibody responses in

harbor seals fed herring from the Baltic Sea.

Environmental Health Perspectives 103:162–167.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

104

Assessing the Risks to Marine Mammal Populations 

from Exposure to Contaminants

John Harwood

 Ailsa Hall

NERC Sea Mammal Research Unit

Gatty Marine Laboratory

University of St. Andrews

St. Andrews, Fife KY16 8LB, UK

Bryan Grenfell

 Department of Zoology

University of Cambridge

Downing Street

Cambridge CB2 3EJ, UK

Introduction

A well-defined methodology has been developed for

assessing the risks to human populations associated

with exposure to contaminants. Methods derived

from environmental epidemiology and

environmental health policy (Hertz-Picciotto 1996)

are used to estimate the risks of exposure and the

likely response to exposure, taking account of the

characteristics of humans who have been exposed

and the environmental variables which are

associated with exposure (Stallones 1988). In many

cases, exposure probabilities and responses cannot

be estimated directly because the potentially

exposed group is too small, or there is a long

latency period between exposure and response. As

a result, estimates of risk are often based on the

shape of dose-response curves derived from

experimental studies of laboratory animals which

are believed to be suitable surrogates for humans.

The assumptions made in this risk assessment

process are often not directly testable, yet the needs

of policy makers are usually so great that this

approach is considered to be an acceptable way of

evaluating the health costs of different actions. The

U.S. National Research Council developed a

conceptual framework (National Research Council

1983) for the process of risk assessment (Figure 6)

that has been widely accepted. This framework has

been extended by the U.S. Environmenal Protection

Agency (EPA 1992) so that it can be used to assess

the risks to the environment from contaminant

exposure, and Monte Carlo techniques can be used

to take account of uncertainties in assumptions

about parameter values and processes (e.g., Cohen

et al. 1996).

However, there is a fundamental difference

between the two approaches. Human risk

assessment is primarily concerned with the risk to

individuals from exposure. Environmental risk

assessment usually requires an additional step, that

is estimating the consequences of the individuals’

responses to exposure for the dynamics of their

population, and, ultimately, the consequences of

these changes in population dynamics on ecosystem

functions. The impacts of contaminants on

individual animals or plants may, of course, be

considered important when they involve species

(like many marine mammals) which have enormous

popular appeal, or endangered species (where the

loss of even a few individuals could prejudice

survival or recovery). 

In this document we consider how the EPA risk

assessment approach can be used to evaluate the

potential impacts of exposure to specific

contaminants (or combinations of contaminants) on

marine mammal populations. We assume that

potentially hazardous compounds have been

identified, and focus our attention on exposure and
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

105

exposure-response assessment, and on risk

characterization (Fig. 6). We show how

mathematical models developed to understand the

effects of parasites on the population dynamics of

their hosts can provide useful insights, and help in

the estimation of key parameters.

Exposure Assessment

We can obtain some information about exposure

from surveys of the concentration and total burden

of contaminants in the bodies of animals found dead

or killed for other purposes. However, for

contaminants which accumulate in particular tissues

– and many of the contaminants of concern for

marine mammals fall into this category – such

measurements do not provide a direct indication of

exposure. Thus it is necessary to model the ways in

which the contaminants have accumulated. There is

a large body of literature that documents models of

the kinetics of contaminants in animal tissues (see,

for example, Walker 1990), but many of the

parameters of these models are difficult to estimate

and likely to be species-specific.

We propose an alternative approach using

stochastic models developed to describe the

accumulation of macroparasites in their hosts (Tallis

and Leyton 1966, 1969). Such models have not

been used widely in parasitology because their

assumptions are usually considered too restrictive

(see, for example, Roberts et al. 1995). However,

most of the assumptions are met in the case of

exposure to contaminants. The distribution of

contaminant burdens (and not the distribution of

concentrations,

Figure 6. The U.S. National Research Council conceptual framework (National Research Council 1983)

for the process of risk assessment, extended by the U.S. Environmental Protection Agency (EPA

1992) to assess the risks to the environment from contaminant exposure. 

 which is what is normally reported in the literature)

among “hosts” is a function of exposure to

contaminated prey, the distribution of contaminant

burdens in prey, the rate at which contaminants are
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

106

metabolized by the “host,” and contaminant-induced

mortality. Tallis and Leyton were able to show that,

even if the distribution of parasites in a vector is

symmetrical, the distribution of parasites in their

hosts is likely to be skewed, and will in many cases

follow a negative binomial distribution. There is a

great deal of data (summarized in Hudson and

Dobson 1995) suggesting that parasite burdens often

provide a good fit to the negative binomial.

However, concentrations of contaminants are

continuous variables and more often conform to a

lognormal distribution, suggesting that

accumulation is the result of a number of processes

whose effect is multiplicative. 

The use of models of this kind allows us to

predict the distribution of contaminant burdens in

marine mammal populations from information on

their diet and the distribution of contaminants in

their prey. Although such information is not easy or

inexpensive to acquire, it can be obtained much

more readily than information on the total body

burden of a large and representative sample of

marine mammals.

Exposure-Response

The next stage in the risk assessment procedure is to

estimate the effect of a specific level of individual

exposure on the probability of survival or fecundity

for that individual (i.e., we need to know the form

of the dose-response curve). As with humans, it is

rarely practicable to estimate such curves directly.

Instead, we must rely on analogy with related

species to provide insight into the form of the doseresponse relationship. 

We may be able to obtain further insight from an

analysis of the distribution of contaminant burdens

or concentrations in “hosts.” Contaminant-induced

mortality does affect the observed distribution of

contaminants in survivors, but the effects of

different exposure-response relationships are

relatively small and would be extremely difficult to

detect, even with (unreasonably) large sample sizes

(Fig. 7, upper). However, the distribution of

contaminants in animals that die (for example

during mass mortality events induced by viral

infection, in which contaminants are believed to

play a contributory role) depends on the form of the

exposure-response curve (Fig. 7, lower). This

suggests that a more detailed analysis of the

distribution of contaminants in animals found dead

could be useful.

Risk Characterization

In order to complete the risk characterization we

need some insight into the potential effects of

contaminant exposure on “host” populations. This

can be obtained by analyzing simple mathematical

models of the processes involved. In such models,

changes in “host” abundance are assumed to depend

on the “host’s” maximum potential rate of increase,

the nature of self-regulation within the “host”

population, and the mortality (or reduction in

fecundity) induced directly or indirectly by

contaminant exposure. Changes in contaminant

burden are assumed to depend on the rate at which

contaminants enter the environment, the rate at

which they are metabolized by “hosts,” and the

input of contaminants from “natural” and

contaminant-induced “host” death.

For contaminants which do not accumulate, it

can be assumed that concentrations in tissues reflect

exposure. Hallam et al. (1983a, b) developed

deterministic models which can be used to

investigate the response of marine mammal

populations to non-bioaccumulating contaminants,

and Gard (1990) extended these models to take

account of stochasticity. The basic equations are

dM/dt = M(r0 – ß(p) – kM)

dp/dt = q – (b+z)p - ß(p)

where M is the abundance of the marine mammal, r0

is the rate of increase at low population density, p is

the average concentration of contaminants in 
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

107

Figure 7. An analysis of the distribution of contaminant burdens or concentrations in “hosts”; the effects

of different exposure-response relationships are relatively small and would be extremely difficult

to detect, even with large sample sizes (upper figure); the distribution of contaminants in animals

that die depends on the form of the exposure-response curve (lower figure).
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

108

the marine mammal population, ß(p) is the

exposure-response relationship, r0/k is the

equilibrium size of the marine mammal population

in the absence of contaminants, q is the rate at

which contaminants enter the environment, and b

and z represent natural mortality and metabolism of

contaminants, respectively.

For contaminants which accumulate, “host”

response is likely to be related to the burden of

contaminants in individual marine mammals. In this

case, equations first developed by Anderson and

May to model the effects of macroparasites on their

hosts (Anderson and May 1978, May and Anderson

1978) are more appropriate:

dM/dt = M(a – b - kM) – ß(P) 

dP/dt = qM – (b+z)P - ßME{i2

}

In these equations, P is the total quantity of

contaminant in the “host” population, and E{i} is

the expectation that an individual marine mammal

will have a burden i. This model therefore takes

explicit account of the observed distribution of

contaminant burdens. If this distribution is lognormal, E{i2

} = (P/M)2; if it is Poisson, E{i2}

=(P/M)2 + P/M; and if it follows the negative

binomial, E{i2

} =(P/M)2 (k+1)/k + P/M. Other

parameters represent the same quantities as in the

Hallam model. 

Both models predict that the presence of contaminants can reduce the rate of recovery of a

depleted population, and reduce its equilibrium size.

The magnitude of these effects is directly related to

the size of q and the form of ß.

Another potentially fruitful approach here is to

adapt moment methods, developed for macroparasites to approximate the stochastic dynamics of

pollutants without assuming an empirical

distribution (Grenfell et al. 1995.)

Multiple Contaminants and Multi-Species

Interactions

The Anderson and May model can be modified

relatively easily to take account of the effects of

combinations of contaminants (see, for example,

Dobson 1985), and their additive, multiplicative,

and interactive effects on “host” mortality.

It is also possible to expand these models to take

account of the fact that contaminants are ingested by

many species in the marine ecosystem. Such

multiple-host, multiple-parasite models are in their

infancy, but it is widely recognized that this will be

a major growth area in epidemiological research

over the next decade. An interesting implication

from analyses of this kind is that an increase in the

abundance of marine mammal species which are

less susceptible to the effects of contaminants may

benefit more susceptible species (provided that there

is not competition between them for other

resources). This is because the less susceptible

species “lock up” or sequester a significant

proportion of contaminant inputs, thus reducing the

exposure of more susceptible species. The large

quantities of organochlorine contaminants which

accumulate in the bodies of sperm whales (Law et

al. 1997), for example, may serve this purpose.

Implications For Future Research

We suggest that the considerable insight into the

potential effects on marine mammals of exposure to

contaminants can be obtained using mathematical

models originally developed to analyze the effects

of macroparasites on their hosts. In addition,

analysis of the distribution of contaminants in

animals found dead, particularly after mass

mortality events in which contaminants are

implicated, can provide much needed information

on the form of the relationship of response to

exposure.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

109

References

Anderson, R. M., and R. M. May. 1978. Regulation and

stability of host-parasite population interactions. I

Regulatory processes. Journal of Animal Ecology

47:219–247.

Cohen, J. T., M. A. Lampson, and T. S. Bowers. 1996.

The use of two-stage Monte Carlo simulation

techniques to characterize variability and uncertainty

in risk analysis. Human and Ecological Risk

Assessment 2:939–971.

Dobson, A. P. 1985. The population dynamics of

competition between parasites. Parasitology 91:317–

347.

EPA. 1992. Framework for Ecological Risk

Assessment. U.S. Environmental Protection

Agency, Risk Assessment Forum, Washington, D.C.

Gard, T. C. 1990. A stochastic model for the effects of

toxicants on populations. Ecological Modelling

51:273–280.

Grenfell, B. T., K. Wilson, V. S. Isham, H. E. G. Boyd,

and K. Dietz. 1995. Modelling patterns of parasite

aggregation in natural populations: trichostrongylid

nematode-ruminant interactions as a case study.

Parasitology 111: S135-S151.,

Hallam, T. G., C. E. Clark, and R. R. Lassiter. 1983a.

Effects of toxicants on population: a qualitative

approach. I Equilibrium environmental exposure.

Ecological Modelling 18:291–303.

Hallam, T. G., C. E. Clark, and G. S. Jordan. 1983b.

Effects of toxicants on population: a qualitative

approach. II First order kinetics. Journal of

Mathematical Biology 18:25–37.

Hertz-Picciotto, I. 1996. Epidemiology and quantitative

risk assessment: a bridge from science to policy.

American Journal of Public Health 85:484–491.

Hudson, P. J., and A. P. Dobson. 1995. Macroparasites:

observed patterns in naturally fluctuating animal

populations. Pages 144–176 in B. T. Grenfell and A.

P. Dobson (eds.), Ecology of Infectious Diseases in

Natural Populations. Cambridge University Press,

Cambridge.

Law, R. J., R. J. Morris, C. R. Allchin, and B. R. Jones.

1997. Metals and chlorobiphenyls in tissues of

sperm whales (Physeter macrocephalus) and other

cetaceans exploiting similar diets. Bulletin de

L’Institut Royal des Sciences Naturelles de Belgique, Biologie 67-Supplement:79–89.

May, R. M., and R. M. Anderson. 1978. Regulation and

stability of host-parasite population interactions. II

Destabilizing processes. Journal of Animal Ecology

47:249–267.

National Research Council. 1983. Risk Assessment in

the Federal Government: Managing the Process.

National Academy Press, Washington, DC.

Roberts, M. G., G. Smith, and B. T. Grenfell. 1995.

Mathematical models for macroparasites of wildlife.

Pages 177–208 in B. T. Grenfell and A. P. Dobson

(eds.), Ecology of Infectious Diseases in Natural

Populations. Cambridge University Press,

Cambridge.

Stallones, R. A. 1988. Epidemiology and environmental

hazards. Pages 3–10 in L. Gordis (ed.),

Epidemiology and Health Risk. Oxford University

Press, Oxford.

Tallis, G. M., and M. Leyton. 1966. A stochastic model

approach to the study of parasite populations.

Journal of Theoretical Biology 13:251–260.

Tallis, G. M., and M. Leyton. 1969. Stochastic models

of populations of helminth parasites in the definitive

host. Mathematical Biosciences 4:39–48.

Walker, C. H. 1990. Kinetic models to predict bioaccumulation of pollutants. Funtional Ecology 4:295–

301. 
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

110

Overview of Federal and International Programs 

on Contaminants in Marine Mammals

Teri K. Rowles

National Marine Fisheries Service

Office of Protected Resources

1315 East West Highway

 Silver Spring, MD 20910 

Lyman K. Thorsteinson 

U.S. Geological Survey

Biological Resources Division

909 First Avenue, Suite 800

Seattle WA 98104

Many marine mammal species bioaccumulate a

variety of environmental contaminants as a

consequence of feeding at high trophic levels in the

food web. Similar accumulation of toxic substances

has been associated with deleterious health effects

in a range of wildlife. Numerous state, federal,

private, and international programs address

contaminant issues in marine mammals. Such

programs can focus on the effects on individual

species, ecosystems, habitat quality, or human

health, and they can involve research, monitoring,

surveys, or the archiving of data or tissues. This

paper provides an overview of several prominent

federal and international programs which directly,

or indirectly, involve investigative activities relating

to environmental contaminants and marine

mammals. We also discuss potential avenues for

scientific coordination.

Most U.S. federally funded marine mammal

programs that address contaminants and their effects

reside in the Department of Commerce (DOC), the

Department of the Interior (DOI), and the

Environmental Protection Agency (EPA). Both the

DOC and DOI have trust responsibilities for marine

mammals and their ecosystems, whereas the EPA

has regulatory authority for the protection of the

natural environment and human health. The DOI’s

Fish and Wildlife Service (FWS) has stewardship

responsibility for sirenians, sea otters, walruses, and

polar bears. All other marine mammals in U.S.

waters fall under the jurisdiction of the DOC’s

National Marine Fisheries Service (NMFS).

Two agencies within the DOC are most directly

involved in research, monitoring, and assessment of

contaminant levels and biological effects in marine

mammals. These are the National Oceanic and

Atmospheric Administration (NOAA) and the

National Institute of Standards and Technology

(NIST). NOAA has management responsibilities

related to the status and protection of marine

mammal populations and stocks as well as their

habitats, under provisions in the U.S. Marine

Mammal Protection Act of 1972 (MMPA) and

subsequent amendments. NMFS is the principal

entity in NOAA entrusted with scientific missions

for assessing environmental effects, including

anthropogenic activities, on these protected

resources. NIST, in collaboration with NMFS, (1)

provides analytical support and technical

cooperation for contaminant quality assurance

analyses through the National Marine Analytical

Quality Assurance Program, and (2) archives marine

mammal tissues in the National Marine Mammal

Tissue Bank as part of the National Biomonitoring

Specimen Bank (NBSB). NOAA’s National Ocean

Services complements NMFS missions through

trustee-related damage assessments or other

analyses associated with its coastal monitoring and
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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benthic surveillance.

In response to monitoring requirements

specified in the MMPA, NMFS initiated a longterm, multidisciplinary program called the Marine

Mammal Health and Stranding Response Program

(MMH&SRP). It is a national program that

involves partnerships within NOAA and other

federal agencies and with numerous state and local

governments and non-government organizations. A

major purpose of the MMH&SRP is to investigate

biological linkages between chemical contaminants

in the marine environment and specific population

health indices or parameters in key populations.

Information about the bioaccumulation and

distribution of toxic contaminants is derived from

samples obtained from marine mammal strandings,

subsistence hunts, bycatch, die-offs, live capturerelease programs, biopsy programs, and disease

investigations. Quality assurance is emphasized in

the MMH&SRP, and participation in the program

requires adherence to standard protocols in the field

and state-of-the-art analytical techniques in the

laboratory. Research collaborations typically

include projects where complementary biological

observations on individual and population health are

available with tissue collections.

Two bureaus within the DOI conduct research

and monitoring with specific objectives for study of

environmental contaminants in marine mammals.

Under the MMPA, FWS has management authority

for certain marine mammals and conducts speciesspecific or site-specific studies through its Marine

Mammal Management and Ecological Services

offices. As an example, FWS is presently studying

contaminants in polar bears and sea otters in Alaska.

The FWS projects tend to be issue-oriented surveys

to establish baseline conditions. The U.S.

Geological Survey, through the Biological

Resources Division (BRD), is involved in a variety

of research projects that address DOI and other

partner needs regarding managed populations, their

habitats, and ecosystems of concern. The BRD

research projects tend to be population-oriented and

three to five years in duration. An exception is the

Arctic Marine Monitoring and Trends Assessment

Program, or AMMTAP (formerly the Alaska

Marine Mammal Tissue Archival Project) which

was initiated in 1987 to develop collection protocols

for sampling and to provide long-term archiving of

marine mammal tissues. The AMMTAP has a long

history of research and administrative collaboration

with NOAA, NIST, FWS, the DOI’s Minerals

Management Service, the State of Alaska, and

various non-government organizations.

Over the last two decades, the EPA has

performed chemical analytical studies on tissues

from marine mammals and other marine organisms

for specific studies or specific sites. As an example,

the EPA participated in the investigation of die-offs

of bottlenose dolphins along the Atlantic coast of

the United States in 1987–1988. In related followup investigations, the EPA has completed several

additional studies on bottlenose dolphins,

particularly in the coastal zone of the eastern United

States. The agency is presently administering

several food-web and subsistence-oriented studies

in Alaska.

Numerous non-government organizations and

international agencies have funded, are currently

funding, or are planning relevant contaminant

research on marine mammal populations of interest

to U.S. management and tribal authorities or

international management bodies. These include

such organizations as the Arctic Monitoring and

Assessment Project (AMAP), the International

Whaling Commission, the United Nations

Environment Programme, the North Slope Borough,

and the World Wide Fund for Nature. Other

international organizations also perform specific

contaminant studies and have long-term

biomonitoring and specimen-banking programs.

Within the United States, major universities have

established cooperative research programs (e.g.,

University of Alaska’s Center for Arctic Research)

and sponsor directed research to answer specific

questions about contaminant pathways, processes,

and probable effects.

A common objective of many research and

monitoring programs has been to determine baseline

levels of heavy metals and persistent organic

pollutants in marine mammal populations. Few
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

112

programs have adequately addressed the numerous

experimental design issues that inevitably arise in

studies of contaminant trends. For example, quality

control and assurance are usually handled at the

laboratory or study level. This has resulted in

numerous problems with data comparability and

repeatability, both ingredients of good science. As

federal and state agencies adopt the precepts of

ecosystem management, there is a growing need to

coordinate, wherever possible, research, monitoring,

and quality-assurance programs at national and

international scales to better address questions about

contaminant origins, transfer, biological fate, and

impacts on marine mammals. The coordination

among NOAA, NIST, and USGS is illustrated by

the respective agency efforts in the MMH&SRP,

NBSB, and AMMTAP in Alaska and by their

contributions to the AMAP. In the future,

government and non-government organizations

should work collaboratively to address issues

related to contaminants in marine mammals.
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Overview of Health, Ecological, and Economic Dimensions of Global Change:

Tracking Marine Disturbance and Disease

William S. Fisher 

US Environmental Protection Agency

National Health and Environmental Effects Laboratory

Gulf Ecology Division

One Sabine Island Drive, Gulf Breeze, FL 32561

Paul R. Epstein

Center for Health and the Global Environment

Harvard Medical School

40 Oxford St., Cambridge, MA 02138

Benjamin H. Sherman

Harvard School of Public Health

Rm 327 Engineering Sciences Lab

40 Oxford St., Cambridge, MA 02138

We introduce the concept and discuss the potential

of a world-wide system for reporting and

documenting marine disease and mortality events.

This information can be useful for determining

causes, trends, impacts, costs, and environmental

conditions. It is generally recognized that morbidity

and mortality of marine organisms occur frequently,

from both natural and anthropogenic causes, and

that reported events represent only a fraction of the

number that occur. Nevertheless, investigation of

such events in the United States is an important

function of the Marine Mammal Stranding Network,

the Sea Turtle Stranding Network, and resource

agencies responsible for managing fish, shellfish,

corals, waterfowl, and other coastal organisms.

Regardless of its limitations, this work is expected

to generate valuable information related to public

health, resource management, and environmental

conditions.

Several important questions are triggered by

marine mortality events, especially those that

involve large numbers of organisms or a “sensitive”

(e.g., endangered or threatened) species. Chief

among these are the following: What was the cause?

Was it related to disease, lethal exposure to a

contaminant, physical trauma, or some other factor?

There is also interest in knowing about aggravating

factors, or contributing stressors. For example, did

rapid changes in temperature or salinity, high

contaminant burdens, or sublethal levels of a biotoxin contribute to the situation? And there are

immediate concerns for human health. Have coastal

residents been exposed to contaminants, toxins, or

pathogens, either directly through air and water or

indirectly through the food chain? Other questions

raised by marine mortality events are broader in

scope. Are such events becoming more frequent,

and are more organisms being affected (trend over

time)? Are events becoming more frequent or more

serious in certain regions (trend over space)? Has

the event or series of events had a significant, longterm impact on population abundance or viability?

Does the event represent a deterioration in

ecological conditions? What was the economic cost

of the event — to fisheries, tourism, and local

economies? And if ecological deterioration is a

factor, what future costs might be expected?

Obviously, many of these questions cannot be

answered by a forensic examination of individual

organisms. Few investigations of marine mortality

include anything more than such an examination,

which is used primarily to determine cause. Perhaps
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

114

we are predisposed to this individual-oriented

approach because so many of the disciplines

represented in the investigations are based in the

science and technology of human health (e.g.,

pathology, microbiology, immunology, etc.), where

the well-being of individuals are a primary focus.

For non-human species, however, concern for

individuals is more often superceded by population

issues, as reflected in the questions above.

Measurements at the population level fall within the

domains of epidemiology (human) and

epizootiology (non-human organisms), applied

scientific disciplines that examine the range, extent,

rate, frequency, and duration of disease or mortality

within a defined population. 

We believe that a comprehensive epizootiological approach is needed to extract some of the

most important information from marine morbidity

and mortality events. To be successful, this

approach should be tailored to provide comparisons

of mortality or morbidity events with other major

marine events (such as harmful algal blooms or

mortalities of other species) and anomalies (such as

climate change, weather, and freshwater intrusions).

Most often, events are investigated as though all

relevant stressors were generated at the local level,

even though they may have originated from, or at

least been influenced by, regional or global

conditions. To ascertain which conditions are most

closely linked to marine mortality events will

require that data from local sources be compiled and

set in a regional or global context. Thus, our

approach must be able to accommodate relevant

time scales (decades or longer) and spatial scales

(ecosystem to global). 

This proposition carries with it several

challenging requirements, foremost of which are the

collection of high-quality data (from a consistent

reporting effort and with standardized reporting

criteria) and a global framework for storing and

relating complex information. Potential prototypes

for meeting these requirements are provided by the

two regional programs described below.

High-Quality Data: The Gulf of Mexico

Aquatic Mortality Network

High-quality data are critical for interpreting marine

morbidity and mortality, yet reporting efforts vary

dramatically from place to place and over time. The

lack of consistency undermines the credibility and

usefulness of the data, particularly when the times

and places of non-events (i.e., when and where

events do not occur) are so important to

interpretation. Additionally, those who report,

document, or respond to mortality events often have

differing standards, credentials, and motives. These

difficulties have been recognized and confronted by

a group of resource managers in the northern Gulf

of Mexico. The Gulf of Mexico Aquatic Mortality

Network (GMNET) is a collaboration among U.S.

state and federal agencies to improve reporting and

interstate communication regarding mortality

events, to standardize response approaches and

documentation, and to promote research in forensic

pathology across the five states bordering the Gulf

of Mexico. A long-term goal is to develop

indicators of ecological conditions for the Gulf of

Mexico based on mortality and disease monitoring

data. Information on current mortality events and

items of recent interest such as the 1996 manatee

die-off associated with red tide can be found at the

GMNET web site (http://pelican.gmpo.gov/gmnet/)

Several attributes of GMNET are instructive

with respect to obtaining high-quality data for a

global epizootiological approach. Consistency and

quality are facilitated by the involvement and

accountability of professionals employed by each

state to investigate mortality events. These resource

managers have adopted standard investigative

procedures. Consistency is fostered through

periodic interstate training exercises. In addition, a

three-tiered data-entry format provides essential

information (Tier 1: what, when, where, how many,

and why); environmental information related to

probable cause (Tier 2: water quality, lesions,

weather conditions, etc.); and state-privileged

information (Tier 3: chain of custody, litigation

information, etc.). Only the first two tiers are

shared in the common database, and the states

maintain control of their own data. The three tiers
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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allow all states to use the same format while

retaining the flexibility to control some types of

information. The regional format of GMNET is

another attribute that might serve a larger program.

GMNET has been organized and implemented by

group members because of their shared interests and

their recognition of the value of neighboring-state

interactions. The GMNET program was introduced

to resource managers in 12 additional states along

the east coast of the United States, and they

overwhelmingly accepted the concept and its future

expansion to their states. A global program might

similarly be initiated in selected regions to

overcome the greatest obstacles, and then be

expanded afterward.

Documentation Framework: The Health,

Ecological, and Economic Dimensions of

Global Change Program

The value of morbidity and mortality data generated

from a global reporting network cannot be estimated

until it is examined in an epizootiological

framework, which requires a relational database

capable of holding large and complex datasets.

Existing data archives are limited in extent (spatial

and temporal), limited in coverage (e.g., marine

mammals only), not always systematically indexed,

and not always available to the public. Current

databases have limited potential for comparisons

with other databases and limited potential to

integrate co-occurrences, trends, and models. 

A relational database for marine disease and

mortality events will be most effective if

constructed using time and space (place) as indices,

or cataloging tools. All events have these two

factors in common. Such a system will demonstrate

co-occurrences with other events and anomalies in

the same database, reveal trends across time and

space, and allow comparisons with other datasets

that are cataloged by time and space, including

population models (stock assessments, migration

patterns), ecosystem models (habitat suitability,

trophodynamic interactions, climate), and economic

models (marketing, tourism). In addition, the use of

time and space to catalog marine events makes it

possible to apply the relatively new and powerful

tool of Geographic Information Systems (GIS).

These systems employ time and space indices to

facilitate the management and analysis of large and

complex datasets. A GIS provides a visual display

of nearness and potential association among

occurrences and anomalies (hypothesis generation),

provides organizational structure to complex datasets through a point-and-click ability to retrieve

complete event records from a map, and ultimately

will provide analytical and statistical tools for

epizootiological research. Once digitized, GIS can

examine data for counts per area, frequency,

distance from point sources, proximity, clustering,

trends, and a variety of current and future

mathematical and interpolative analyses.

The Health, Ecological, and Economic

Dimensions of Global Change Program (HEED

Program) (http://heed.harvard.edu) has recently

developed a relational database to retrospectively

compare major marine ecological disturbances,

including infectious disease epizootics, mass

mortality events, harmful algal blooms, and

anomalous changes in marine species abundance

and composition. The objectives of the program

include detection of declines in ecosystem health,

achieving a better understanding of the causes and

consequences of environmental change, evaluating

the ultimate impact on human health, and estimating

market-related costs. The HEED Program links data

from disparate ecological, climatic, and economic

datasets to identify co-occurrences of recognized

anomalies. Datasets include (1) biological events,

e.g., diseases and deaths of marine organisms,

harmful algal blooms, and marine-related human

diseases, (2) climate anomalies, and (3) biophysical

characteristics (e.g., water quality, hydrology).

Data from the last 40 years, ranging geographically

from Labrador (Canada) to Venezuela and including

the Caribbean and the Gulf of Mexico, were

obtained from science journal articles, mass media,

government reports, and interviews with scientists

and resource managers. This retrospective database

includes event data for marine mammals, corals,

seagrasses, bivalves, sea turtles, marine birds, fish,

invertebrates, algae, and human health (related to
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

116

marine events). These have been integrated into a

GIS that assists in hypothesis generation and

supports ecosystem and economic models.

The relational framework for documentation of

events supports an epizootiological approach, and

that is the primary attribute of the HEED Program

that can be applied to a global mortality monitoring

system. The ability to compare with related factors

in the same database and with external databases

using a GIS format is highly desirable. Although

currently holding only historical data, the

framework is a promising prototype for

documentation of future events. It may also be

scaled from a regional framework to a global

framework.

A Convergence of Prototypes 

The GMNET and HEED programs offer potential

resolutions to the foremost challenges of developing

a global marine morbidity and mortality database

that can be applied in an epizootiological

perspective. We believe that the concept of having

trained, accountable personnel use standardized

procedures and data-entry formats, as in the

GMNET program, can be duplicated at a larger

scale (continent or large marine ecosystem) to

provide consistent, high-quality data. A tiered dataentry format can provide continuity in reporting

while retaining flexibility for participating

countries. Reporting in a global system would have

to be limited to major marine events and not include

all of those reported in the GMNET program. A

global network might be attained through sequential

additions of regions, such as those defined by the

Large Marine Ecosystem (LME) Program. The

HEED documentation framework was designed as

a hypothesis-generating epizootiological tool, and it

should be easy to expand it to a global scale. As

LME’s are added to a global network, retrospective

data searches could be used to establish a historical

baseline.

We propose a convergence of concepts

identified in these two programs for investigating,

documenting, and tracking marine disease and

mortality in a global, epizootiological context. Just

as epidemiologists track insect and rodent vectors

and microorganisms that infect humans, we will be

able to track indicators, such as harmful algae and

marine pathogens that respond rapidly to

environmental change, to predict public health,

ecosystem, and economic threats.
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A Framework for Analyzing the Origins of Contaminants 

in Marine Mammals

Peter L. Grose

Daniel J. Basta

Thomas F. LaPointe

National Oceanic and Atmospheric Administration

National Ocean Service

Special Projects Office, SSMC#4 Room 09449

1305 East West Highway

Silver Spring, MD 20910

Introduction

This paper proposes a model process for

determining the probable origins of contaminants in

marine mammals. The process begins as an

intellectual effort to analyze the problem from two

perspectives — contaminants and their sources, and

marine mammals that accumulate contaminants in

their body tissues. The next steps are to identify

key components of the model and to establish a

framework for obtaining, organizing, and analyzing

the required data. The desired outcome is to

determine the origins of specific contaminants

found in selected marine mammal populations.

Initial Considerations

There are many contaminants of interest, but for

simplicity we consider four groups: lipophilic

organics, toxic metals, agricultural contaminants,

and plasticizers and industrial solvents. Lipophilic

organics are important because they biomagnify as

they pass through the food web. PCBs and DDT are

primary examples of this group. Toxic metals occur

in both inorganic and organic forms, with the

organic forms typically being more biologically

active. Mercury and tin are primary examples of

this group. Agricultural contaminants include

pesticides, herbicides, and fungicides, some of

which can be active at very low doses. Plasticizers

and industrial solvents are known carcinogens.

There are more than 100 species of marine

mammals in six taxonomic groups: pinnipeds,

baleen whales, toothed whales, sirenians, the sea

otter, and the polar bear. Each group is

fundamentally different with respect to life history

and behavior. Within the groups, further

differences exist between species and often between

populations.

Contaminants enter the environment as

waterborne pollutants from point sources (e.g., pipes

or spills) or non-point sources (e.g., runoff), or as

aerosols and particulates (e.g., dust from agricultural

activities, vapors from pesticide applications, and

industrial emissions). Transport is affected by

estuarine, oceanic, and wind circulation as well as

by the migratory behavior of contaminated prey.

Contaminants can enter a marine mammal

through any of four pathways: mouth, skin, lungs,

or transfer from mother to fetus. The two most

important pathways are thought to be those

involving food consumption (including mother’s

milk) and prenatal mother-offspring transfer. A

substantial amount of a mother’s contaminant

burden is passed directly to her offspring, especially

the first-born, via nursing. This is beneficial to the

mother as it very effectively decreases her burden of

contaminants. After weaning, consumption of

contaminated food is probably the most important

pathway for contaminants to enter marine mammals.
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Generating a Framework

A framework for determining the origins of

contaminants in marine mammals is shown in

Figure 8. The framework’s key components are

C Opportunistic sampling of stranded and bycaught animals, sampling from directed hunts,

and non-destructive biopsy sampling from freeranging animals.

C Field and controlled experimental data to

develop information on the uptake and

degradation of contaminants. 

C Data on life history and seasonal distribution of

marine mammals and their prey.

C Environmental climatology, which supplies

information on contaminant movements and on

stresses that can exacerbate the effects of

contaminants or alter uptake pathways.

C Contaminant sources (i.e., where contaminants

are manufactured and used, and how they are

disposed).

C Marine mammal prey and their life histories to

elucidate trophic pathways.Knowledge of the

wider scientific community, especially for

extrapolating information between species and

between contaminants. Contributors would

involve not only the extended marine

mammalogy and contaminants communities

represented at this workshop, but also chemists,

physical oceanographers, and meteorologists.

C Tools to perform relatively simple analyses,

such as spatial coincidence and likelihood

inferences.

These components can be grouped functionally

into four types of activity: (1) collection of

information, especially updating and adding new

data to the existing knowledge base; (2) assembly of

key data into accessible and operable sets; (3)

hypothesis framing with simple analytical tools; and

(4) analyses in time and space (overlays), which

lead to joint exposure analyses, which in turn lead to

likelihood statements relating sources and

destinations.

Discussion of the Components

Opportunistic Sampling of Marine Mammals

and Controlled Experiments. Given the political

climate and the endangered or protected status of

marine mammals in much of the world, deliberately

lethal sampling is generally impractical. Likewise,

it is impractical to expect that sufficient and

appropriate data on contaminants and physiology

will become available from strandings alone. Every

opportunity to obtain data needs to be pursued,

including sampling from by-caught, live-stranded,

and dead but fresh stranded animals, animals in

rehabilitation programs, and free-living animals

(through collection of non-destructive biopsies).

Controlled experiments on captive animals are also

necessary to elucidate effects and the mechanisms

that cause them. A critical aspect of this data

collection is that the data be made readily available

to multiple users.

Data on Life History and Distribution. Many

marine mammal populations can be assigned to one

of three categories based on movement patterns:

local populations, coastal migrators, and pelagic

species. The life histories and distributions of local

populations are relatively well known because they

are readily available for observation and study.

Less well known are the populations that migrate

along the coasts. Most of what is known about

these populations comes from observations made as

they pass along a coastline and are, therefore,

accessible. Least well known are the highly

migratory pelagic species which spend most of their

lives well away from the coast.

Environmental Climatology. With the advent in

1978 of satellite sensors collecting marine

environmental data, we have a good understanding

of “average” ocean circulation, wind patterns, and

sea surface temperature distributions at scales

approaching a few tens of miles. Because these data

are collected routinely, we can also detect monthly

or seasonal deviations from the average conditions

over decades or longer time periods. This offers the

potential to identify stresses which might confound

analyses of animal responses to contaminants (e.g.,
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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by altering normal supplies of prey or causing

migration patterns to vary). Available datasets

include the 11 CD-ROMs describing the World

Ocean Circulation Experiment. Global Data version

1.0, published by NOAA’s National Oceanographic

Data Center in 1998, and monthly summaries.

Contaminant Sources. All of the contaminants of

interest continue to be manufactured and used.

Also, substantial quantities are stored either in

sediments and industrial stockpiles or as trophic

burdens in food webs. Because of increased

regulation in developed countries, much of the

production has moved to other areas where the

details of production and disposal are unavailable.

Environmental non-government organizations and

inter-government organizations such as the World

Bank and the World Heath Organization are the

main sources of data on current production and

discharge levels of persistent contaminants.

Trophic Pathways. A major pathway of

contaminants into marine mammals is food-chain

biomagnification. Data on distributions and

contaminant burdens of some marine mammal prey

species are available, particularly for commercial

fish and shellfish. Such data are rarely available,

however, for non-commercial species. The two

aspects of this component are the identification of

which prey species are relevant, and then the

collection of information on their life histories and

distributions. The latter is most likely to come from

the fisheries literature. Contaminant burdens of the

prey species also need to be measured or estimated.

Knowledge of the Scientific Community.

Probably the most important component of the

framework is the knowledge and expertise of the

broad-based scientific community. It will never be

possible to answer all relevant questions

definitively, and many extrapolations and inferences

will be necessary. Making these will require

multidisciplinary studies and novel types of

collaboration. The proposed framework begins with

the formulation of hypotheses relating marine

mammals to their prey, contaminants, and

environmental interactions. These largely

biological models need to be tested using

deterministic and statistical techniques with both

target and surrogate species.

Tools and Analyses. Exposure analysis and

likelihood inferences will rely on both simple and

sophisticated tools and analyses. Simple spatial

overlays of marine mammal populations, prey, and

contaminants can be used to infer likelihood of

hypothesized pathways and interactions. Estimates

of contact time (co-occurrence) can also be derived

from these overlays. Joint exposure analyses are the

next analytical step: quantifying where and for how

long each life stage is exposed to contaminated

prey, and quantifying the exposure of prey to

contaminant sources. The biological-process

models can be tested using inferred and/or

extrapolated uptakes and efficiencies, and

probabilistic statements can be made about cause

and effect. These models can also be used to set

limits on uptake models and identify gaps in the

data.

Considerations for Initial Steps

Implementing a framework such as the one

proposed here will be difficult and will require

considerable input from the scientific community.

It is important to start with simple approaches and to

add complexity in an incremental manner. The

framework should be designed to grow and expand.

People who will use the data and results need to be

involved at all stages of implementation. Those

who supply data and information must receive value

for their time and effort, so feedback is essential.

Based on these considerations, implementation

might focus initially on data collection from

opportunistic sampling, using a form-based datacollection system. The data can be entered using

hardcopy, softcopy, or on-line tools. Suppliers of

data could receive feedback (added value) via a

built-in mapping system, using either a host-resident

mapper or a user-based desktop system, such as the

no-cost ArcExplorer from Environmental Sciences

Research Institute. In this way, maps could be

delivered showing where data have been collected.

Candidate forms for data collection already exist

and are published in the recently released CD-ROM
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121

“Marine Mammals Ashore: A Field Guide for

Strandings” (available from the National Aquarium

in Baltimore). Future expansion of the system could

include mail relay to facilitate information exchange

and an on-line encyclopedia of knowledge about life

histories and spatial distributions of marine

mammals.
122

Section V. APPENDICES

Appendix A: Workshop Participants

Richard F. Addison

Head, Contaminants Science Section

DFO Institute of Ocean Sciences

PO Box 6000

9860 West Saanich Road

Sidney, British Columbia V8L 4B2

CANADA

A. Alonso Aguirre

International Field Wildlife Veterinarian

Wildlife Preservation Trust International

Clinical Professor

Center for Conservation Medicine

Tufts University School of Veterinary Medicine

200 Westboro Road

North Grafton, MA 01536

Kimberlee Beckmen

Research Associate/Wildlife Veterinary Resident

Institute of Arctic Biology

University of Alaska, Fairbanks

PO Box 757000

Fairbanks, AK 99775-7000

Pierre Béland

460 Champ-de-Mars #504

Montreal, Quebec H2Y 1B4

CANADA

Anders Bergman

Veterinary Senior Scientist

Contaminant Research Group

Swedish Museum of Natural History

Naturhistoriska riksmuseet

Box 50 007, Frescativägen 44

S-104 05 Stockholm SWEDEN

Michael J. Carvan III

Research Assistant Professor

Department. of Environmental Health

Kettering Laboratory

University of Cincinnati Medical Center

Cincinnati, OH 45267-0056

Michael A. Castellini

Alaska SeaLife Center

Seward, AK 99664

Theo Colborn

World Wildlife Fund

1250 24th Street NW

Washington DC 20037

Sylvain De Guise

Department of Pathobiology

University of Connecticut

61 N. Eagleville Road, U-89

Storrs, CT 06269

Robert L. DeLong

National Marine Mammal Laboratory

NMFS, Bldg. 4

7600 Sand Point Way N.E.

Seattle, WA 98115

Douglas P. DeMaster

Director, National Marine Mammal Laboratory

NMFS-NOAA

7600 Sand Point Way N.E.

Seattle, WA 98115

Patricia A. Fair

Chief, Living Marine Resources Division

NOS-Center for Coastal Environmental Health 

and Biomolecular Research at Charleston

P.O. Box 12607

Charleston, SC 29412

William S. Fisher

Research Biologist

National Health and Environmental Effects

Research Laboratory

Center for Marine and Estuarine Disease Research

U.S. Environmental Protection Agency

1 Sabine Island Drive

Gulf Breeze, FL 32561-5299
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

123

Michel Fournier (Steering Committee)

Director, Laboratoire de Recherche en

Toxicologie de l’Environnement 

University of Quebec at Montreal

INSR-SANTE

245 Boulevard Hymus

Point-Claire, Quebec H9R 1G6

CANADA

Joseph R. Geraci (Steering Committee)

Senior Director, Biological Programs

National Aquarium in Baltimore

501 E. Pratt Street

Baltimore, MD 21202

Edward D. Goldberg

Professor of Chemistry

Scripps Institution of Oceanography

Marine Research Division

2258 Ritter Hall

8602 La Jolla Shores Drive

La Jolla, CA 92037

L. Earl Gray, Jr. (Steering Committee)

Research Biologist and Toxicologist

Reproductive Toxicology Division, Mail Drop 72

National Health and Environmental Effects

Research Laboratory 

U.S. Environmental Protection Agency

2525 East Highway 54

Research Triangle Park, NC 27711

Peter L. Grose

NOAA-NOS-Special Projects Office

SSMC#4 Room 09449

1305 East-West Highway

Silver Spring, MD 20910

Francis Gulland

The Marine Mammal Center

Marin Headlands

Golden Gate National Recreation Area

Sausalito, CA 94965

Romona Haebler

Research Veterinary Medical Officer

U.S. Environmental Protection Agency

AED/NHEERL/ORD

27 Tarzwell Drive

Narragansett, RI 02882 

Ailsa Hall

Sea Mammal Research Unit

Gatty Marine Laboratory

University of St. Andrews

St. Andrews, Fife 

KY16 8LB SCOTLAND

Larry J. Hansen

Fishery Biologist

NMFS-Charleston Laboratory

219 Fort Johnson Road

Charleston, SC 29412

John Harwood

Sea Mammal Research Unit

Gatty Marine Laboratory

University of St. Andrews

St. Andrews, Fife

KY16 8LB SCOTLAND

Robert J. Hofman (Steering Committee)

Scientific Program Director

U.S. Marine Mammal Commission

4340 East-West Highway, Room 905

Bethesda, MD 20814

Steven D. Holladay

Associate Professor

Biomedical Sciences and Pathobiology

Virginia Tech

Phase II, Room 216, Duckpond Dr.

Blacksburg, VA 24061-0442

Walter M. Jarman

Research Assistant Professor

Civil and Environmental Engineering

Energy and Geosciences Institute

University of Utah

421 Wakara Way, Suite 125

Salt Lake City, UT 84108

Paul D. Jones

Environmental Scientific Research

169 Whites Line East, Unit 6

Lower Hutt, NEW ZEALAND

John Kucklick

Research Biologist

National Institute of Standards and Technology

Charleston Laboratory

219 Fort Johnson Road

Charleston, SC 29412

Alison Kirk Long (Steering Committee)
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

124

Program Officer

U.S. Marine Mammal Commission

4340 East-West Highway, Room 905

Bethesda, MD 20814

Peggy Krahn

Manager, Environmental Technology

and Assessment Branch

Northwest Fisheries Science Center

National Marine Fisheries Service

2725 Montlake Blvd. E

Seattle, WA 98112-2097

Thomas P. Lipscomb

Department of Veterinary Pathology

Armed Forces Institute of Pathology

Washington, DC 20306-6000

Mary Baker Matta

Hazardous Materials Assessment

and Response Division

Coastal Resource Coordination Branch

National Ocean Services

7600 Sand Point Way, N.E.

BIN C15700

Seattle, WA 98115

Robert H. Mattlin

Assistant Scientific Program Director 

U.S. Marine Mammal Commission

Room 905

4340 East-West Highway

Bethesda, MD 20814

Michael J. Moore

Research Specialist

Woods Hole Oceanographic Institution

MS 33, Biology Department

Redfield 244

Woods Hole, MA 02543-1049

Derek Muir

Research Scientist

NWRI-Environment Canada

867 Lakeshore Rd

Burlington, Ontario L7R 4A6 CANADA

Ross Norstrom

Research Scientist

Environment Canada

100 Gamelin Blvd.

Hull, Quebec K1A 0H3 CANADA

Todd O’Hara

Research Biologist

Department of Wildlife Management

North Slope Borough

PO Box 69

Barrow, AK 99723

Thomas J. O’Shea (Steering Committee)

U.S. Geological Survey

Midcontinent Ecological Science Center

4512 McMurry Ave

Fort Collins, CO 80525-3400

Jonathan Phinney

Center for Marine Conservation

1725 DeSales Street NW, Suite 600

Washington, DC 20036

Michelle Reddy

SAIC Maritime Services Division

3990 Old Town Avenue, Suite 105A

San Diego, CA 92110

Randall R. Reeves (Rapporteur)

Okapi Wildlife Associates

27 Chandler Lane

Hudson, Quebec JOP 1H0

CANADA

John S. Reif (Steering Committee)

Professor of Epidemiology

Department of Environmental Health

Colorado State University

Fort Collins, CO 80523

Peter J. H. Reijnders

Institute for Forestry & Nature Research

Dept. of Ecosystem Health

P.O. Box 167

1790 AD Den Burg THE NETHERLANDS

John E. Reynolds III

Professor of Marine Science

Biology and Marine Science Departments

Eckerd College

4200 54th Avenue, South

St. Petersburg, FL 33711
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

125

Robert W. Risebrough

Research Ecologist

2711 Piedmont Avenue

Berkeley, CA 94705

Rosalind Rolland

Assistant Professor

Center for Conservation Medicine

Tufts Veterinary School

200 West Boro Rd

North Grafton, MA 01536

Peter S. Ross 

Contaminants Science Section

DFO Institute of Ocean Sciences

PO Box 6000

9860 West Saanich Road

Sidney, British Columbia V8L 4B2

CANADA

Teri Rowles (Steering Committee)

Fishery Biologist

Office of Protected Resources

National Marine Fisheries Service

1315 East-West Highway

Silver Spring, MD 20910-3226

Lori Schwacke

Department of Biometry and Epidemiology

Medical University of South Carolina

1100 Rutledge Tower

Charleston, SC 29403

John Stein

Director, Environmental Conservation Division

Northwest Fisheries Science Center

National Marine Fisheries Service

2725 Montlake Blvd. E

Seattle, WA 98112-2097

Shinsuke Tanabe

Dept. of Environment Conservation

Ehime University

Tarumi 3-5-7

Matsuyama 790 JAPAN

Nancy J. Thomas

U.S. Geological Survey

National Wildlife Health Center

6006 Schroeder Road

Madison, WI 53711-6223

Geoff Weston York

Biologist

Alaska Marine Mammal Tissue Archival 

Project

U.S. Geological Survey

Alaska Biological Science Center

1011 East Tudor Road

Anchorage, AK 99503-6199

C. J. van Leeuwen

RIVM/CSR

P.O. Box 1

3720 BA Bilthoven 

THE NETHERLANDS 

Randall S. Wells

Conservation Biologist

Chicago Zoological Society

c/o Mote Marine Laboratory

1600 Ken Thompson Parkway

Sarasota FL 34236
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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Appendix B: Workshop Agenda 

Monday Evening, 12 October 1998

 

7:00 PM Welcome, introductions, and review of workshop objectives and format 

(Conveners)

7:20 PM Plenary Address 1. Environmental Contaminants and Marine Mammals: A 

Retrospective Overview. Thomas J. O’Shea and Shinsuke Tanabe

8:00 PM Discussion (Working Group Leaders)

8:30 PM Mixer (cash bar)

Tuesday, 13 October 1998

7:45 AM Announcements

8:00 - 8:30 Plenary Address 2. Reproductive and Developmental Effects of Endocrine

Disrupting Chemicals in Marine Mammals. Peter J. H. Reijnders 

8:30 - 9:00 Discussion. Panelists: Richard Addison, Pierre Béland, Anders Bergman,

Robert DeLong (Leader)

9:00- 9:30 Plenary Address 3. Contaminants and Marine Mammal Immunotoxicology and

Pathology. Sylvain De Guise, Steven D. Holladay, and Kimberlee B.

Beckmen

9:30 - 10:00 Discussion. Panelists: Pierre Béland, Michel Fournier, Ailsa Hall, Steven

Holladay, Nancy Thomas (Leader)

10:00- 10:30 Break

10:30-11:00 Plenary Address 4. Assessing the Risks to Marine Mammal Populations from

Exposure to Contaminants. John Harwood, Ailsa Hall, and Bryan Grenfell 

11:00-11:30 Discussion. Panelists: Theo Colborn, Doug DeMaster, John Reif (Leader) Peter

Ross, Kees van Leeuwen.

11:30-12:00 Plenary Address 5. Overview of Federal and International Programs on

Contaminants in Marine Mammals. Teri K. Rowles and Lyman Thorsteinson.

12:00-12:30 Discussion. Panelists: Paul Jones, John Kucklick, Mary Matta, Derek Muir

(Leader), Peter Reijnders

12:30-1:45 Lunch

1:45-2:15 Plenary Address 6. Overview of Health, Ecological and Economic Dimensions

of Global Change: Tracking Marine Disturbance and Disease. William S.

Fisher, Paul R. Epstein, and Benjamin H. Sherman.

2:15-2:45 Discussion. Panelists: Alonso Aguirre, Frances Gulland, Thomas Lipscomb, Teri Rowles (Leader)

2:45-3:15 Plenary Address 7. A Framework For Analyzing The Origin of Contaminants in

Marine Mammals. Daniel J. Basta, Thomas F. La Pointe, and Peter L. Grose

(Presenter)

3:15-3:45 Discussion. Panelists: R. F. Addison, Joseph Geraci (Leader), Ross Norstrom,

Shinsuke Tanabe

3:45-4:15 Break

4:15-5:30 Review of Terms of Reference and Initial Meetings of Working Groups

5:30-7:00 Break (Dinner)

7:00 PM Continuation of Working Group Organizational Meetings
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

127

Wednesday, 14 October 1998

8:00-10:00 AM Working Groups and Subgroups in Session

10:00-10:30 Break

10:30-12:00 Working Groups and Subgroups in Session

12:00-1:30 Lunch

1:30-3:30 Working Groups and Subgroups in Session

3:30-4:00 Break

4:00-6:00 Working Groups in Session to Discuss and Consolidate Subgroup Reports

6:00-8:00 Dinner

8:00 PM Working Groups in Session to Discuss and Consolidate Subgroup Reports

Thursday, 15 October 1998

7:30-10:00 AM All Participants Convene and Main Working Groups Report to Floor

7:30 Report of Working Group on Endocrinology and Reproduction 

8:00 Report of Working Group on Immunotoxicity, Pathology and Disease

8:30 Report of Working Group on Risk Assessment

9:00 Report of Working Group on Future Trends

9:30 General Workshop Discussion

10:00-10:30 Break

10:30-12:00 Working Groups and Subgroups in Session to Complete Final Report

12:00 - 1:30 Lunch

1:30-3:30 Working Groups and Subgroups in Session to Complete Final Report

3:30-4:00 Break

5:00 Written Working Group Reports Delivered to Workshop Report Editor
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

128

Appendix C:

Overview of Federal Programs That Address Issues Related to

Contaminants in Marine Mammals

Teri Rowles

NOAA Fisheries, Office of Protected Resources, Silver Spring, MD, USA.

Lyman Thorsteinson

U.S. Geological Survey, Biological Resources Division, Seattle, WA, USA.

Introduction

Many marine mammals bioaccumulate high levels

of contaminants as a consequence of their position

at or near the apex of marine food webs and their

geographic range. All marine mammals have had

some degree of exposure to chemical pollution. The

uptake and accumulation of potentially toxic substances (e.g., pesticides, industrial chemicals, and

trace elements) is of concern because adverse effects

have been observed in many wildlife species. In

addition, high levels of contaminants have been

implicated in several die-offs of large numbers of

marine mammals. Thus, there is a need to establish

baseline health and contaminant loads in marine

mammals (Becker et al. 1994). The presence of

contaminants often reflects degradation in marine

environmental quality and long-term threats to

ecosystems. In response to these concerns, management authorities (federal and state governments),

private organizations, and international consortia

have worked independently and in concert to identify exposure pathways and to assess biological

effects of contaminants in marine ecosystems.

Many studies have been short-lived, tactical responses intended to meet the specific need for

mitigative or preventive measures (Waring 1998).

Other short-term efforts have focused on human

health and risk assessments associated with consumptive pathways. Longer-term, strategic programs are rare and expensive, and they require

extensive scientific cooperation. Long-term multidisciplinary approaches are needed to understand

regional contaminant trends, ecosystem conditions,

and animal health.

U.S. Federal Programs

U.S. research and management responsibilities for

the health and protection of marine mammals

reside in several governmental agencies. Most

prominently, these include the Departments of

Commerce (DOC) and the Interior (DOI) and the

Environmental Protection Agency (EPA). The

DOC and DOI have trust responsibilities that

include marine mammal research, management, and

enforcement activities (e.g., DOI 1997, DOC,

1998). Manatees (Trichechus manatus), sea otters

(Enhydra lutris), walruses (Odobenus rosmarus),

and polar bears (Ursus maritimus) are managed by

the DOI’s Fish and Wildlife Service (FWS); all

other marine mammal species are managed by the

DOC’s National Oceanic and Atmospheric Administration’s (NOAA's) National Marine Fisheries

Service (NMFS). The EPA mission is broader and

gives the agency regulatory authority to protect the

natural environment and human health. Occasionally, the Department of Health and Human Services

conducts relevant studies to better understand

contaminant exposure pathways (e.g., subsistence

use) and risks to human health (e.g., Egeland et al.

1998).

Two agencies within the DOC — NOAA and

the National Institute of Standards and Technology

(NIST) — are directly involved in marine mammal

research, monitoring, and assessment of

contaminant-related effects. NOAA’s research and

management responsibilities are described in the
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

129

Marine Mammal Protection Act of 1972 (MMPA).

Within NOAA, NMFS is the principal scientific

entity entrusted with developing information to

assess the effects of environmental change, natural

and anthropogenic, on protected marine mammal

species and habitats. The NIST, in collaboration

with NMFS and others, provides (1) chemical

analytical support and cooperation for quality

assurance analyses through the National Marine

Analytical Quality Assurance Program, and (2)

archiving of marine mammal tissues in the National

Marine Mammal Tissue Bank as part of the National

Biomonitoring Specimen Bank (NBSB). NOAA’s

National Ocean Service (NOS) complements NMFS

missions through benthic monitoring efforts (e.g.,

mussels and sediments) within the Coastal Oceans

Program and through its resource damage assessments conducted following oil spills or other contamination events.

NMFS initiated a long-term, multidisciplinary

program — the Marine Mammal Health and Stranding Response Program (MMHSRP, see Becker et al.

1994) — following amendment of the the MMPA in

1992. Today, the MMHSRP provides scientific

oversight and coordination for most of the DOC’s

health and effects research on marine mammals. It

is a national program that depends on partnerships

within NOAA, with other state and federal agencies,

and with numerous local governments, non-governmental organizations, and volunteers. The MMPAmandated goals for the MMHSRP are to (1) facilitate the collection and dissemination of baseline data

on the health and health trends in marine mammal

populations; (2) correlate the health of individuals

and, wherever possible, populations with available

environmental information; and (3) coordinate

effective emergency responses to strandings and

unusual mortality events. One emphasis of the

program is to describe contaminant transport pathways through marine food webs and, ultimately, to

provide an understanding of the biological effects of

contaminants on marine mammal populations. A

veterinary–ecotoxicological design approach has

evolved where physical, biological, and chemical

measurements are being related to a suite of life

history features (e.g., age, sex, parity, genetics) and

animal health condition factors (e.g., histology,

pathology, and serology) (DOC 1998).

The main administrative functions of the MMHS

RP include (1) coordination and management of

stranding networks and emergency responses; (2)

biomonitoring, including research and assessments;

(3) cryogenic banking for trend monitoring; (4)

chemical quality assurance and control; and (5)

information management and outreach. Tissue

sources in the biomonitoring include subsistence

hunts, strandings and unusual mortality events,

fishery bycatch, live capture and release programs,

and opportunistic sampling (e.g., ongoing research

and monitoring programs).

Contaminant issues have played a major role in

guiding the planning, program development, and

conduct of the MMHSRP. Obtaining adequately

large and representative samples is always a challenge in a program that depends so much on opportunistic sampling. Thus, some of the research

questions being addressed within the MMHSRP

concern monitoring protocols, statistical approaches, and methods development as they pertain

to field collections, specimen banking, and analytical chemistry. Additional, more focused, speciesoriented studies involving controlled experiments

are underway, or are planned, to develop baseline

physiological profiles of healthy captive animals as

references for similar observations from the wild.

NMFS’s Northwest Fisheries Science Center

(NWFSC) is the NOAA lead for analytical chemistry and contaminants monitoring in the MMHSRP.

Other NMFS science centers, field personnel, and

NOAA partners are actively involved in other

aspects of the program. The MMHSRP components

and partnership roles are briefly summarized below.

Marine Mammal Stranding Networks: Stranding

networks are an integral part of the MMHSRP and

have contributed significantly to scientific understanding of species life history, marine mammal

diseases, contaminant processes, and population

health and mortality. In addition, they play a

crucial role in the detection, investigation, and

scientific response to strandings and unusual mortality events. In the last decade, and especially
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

130

through the MMHSRP, NMFS has enhanced its

overall capability through coordination, training

(NMFS personnel, participating scientists, and

volunteers), and public outreach in support of

stranding response. A national coordinator and five

regional coordinators oversee, coordinate, and

authorize all network activities. The quick response

of NMFS and other network participants to stranding events is critical to the quantity and quality of

information obtained. During each mortality event,

a MMHSRP-designated on-site coordinator and

research team assess the event, which may include

toxicant exposure and effects, and prepare a final

report. Response guidance to this team is developed

by NMFS’s Working Group on Marine Mammal

Unusual Mortality Events (Wilkinson 1996). Since

1990 there have been 16 marine mammal mass

mortality events internationally, 13 of which were in

the United States (Vidal and Gallo-Reynoso 1996).

Biomonitoring Program: This program attempts to

integrate medical and ecological disciplines to

provide a holistic investigative approach to health

assessment. The goal is to develop reliable, consistent methods for assessing individual and population

health within the broader contexts of population

ecology and environmental change. The biomonitori

ng elements address biological effects, analytical

methodology, case study research, and quality

assurance and control (Becker et al. 1994). Initially,

new techniques, quality assurance, and standardization (e.g., collection, analysis, and reporting) were

major concerns. With respect to contaminant trends

or effects detection, chemical analyses are conducted on target organs and tissues that are known

or suspected to be important sites for bioaccumulatio

n.

Necropsies are performed on as many animals

as circumstances allow (e.g., Dierauf 1994). In

some instances, ambient environmental conditions,

an animal’s physical state, or other logistical problems preclude necropsies and collection of high

quality, non-degraded tissues. Under the best field

conditions, a suite of biological measurements (e.g.,

size, sex, reproductive status), and observations

(general health and condition) are obtained for every

animal sampled. In addition, trained field workers

collect soft tissue or other biological samples (e.g.,

teeth) for specific laboratory purposes (e.g., age

estimation, contaminants, gross pathology, histopatholog

y, serology, genetics, biomarkers). Analyses of

contaminants are performed by the NWFSC, and in

some instances, by other MMHRSP partners such as

the NIST. Recent case-specific research has included contaminant exposure studies on killer

whales in Prince William Sound, Hawaiian monk

seals on the Leeward Islands, and bottlenose dolphins off California, in the Gulf of Mexico, and

along the mid-Atlantic states of the United States.

Efforts to correlate contaminant residues with

observed biomedical effects include MMHSRPfunded studies of transitional cell carcinomas in

California sea lions, immunological profiles of

northern fur seals, and cardiovascular and renal

disease in rough-toothed dolphins.

Scientific partnerships and coordination within

the MMHSRP allow NOAA to address priorities in

areas where the agency’s own capabilities and

expertise are limited, lacking, or unavailable due to

other commitments. For instance, specialized

necropsies are conducted and biopsies are analyzed

for NOAA by scientists from the Armed Forces

Institute of Pathology and other veterinary pathologists. Similarly, serological studies are conducted

by the U.S. Department of Agriculture’s (USDA's)

National Veterinary Services Laboratory and other

clinical laboratories possessing specialized knowledge about infectious diseases in wildlife. These

investigations have identified causative agents

through cell cultures, molecular approaches (e.g.,

polymerase chain reaction DNA), and morphological examinations. Current research is addressing

the prevalence of morbillivirus, herpesvirus, and

brucella in marine mammal populations (e.g.,

northern sea lions). The combination of veterinary

medical, toxicological, and other environmental

objectives in conjunction with existing population

research (e.g., status and trends) provides the

mechanism for integrated assessments of population

health status and evaluations of threats from contaminants and other stressors. 

Specimen Banking: The requirement for a wellorganized scientific specimen bank for marine
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

131

mammals was recognized by NOAA and others in

the mid-1980s (e.g., Lauenstein and Calder 1988).

Initially, the need was to preserve reference materials for contaminant trend analyses. This led eventually to the formation of NOAA’s National Marine

Mammal Tissue Bank (NMMTB). Long-term

banking objectives meant that methodologies had to

be developed for field sampling and preservation of

tissue specimens in a state that is representative of

the animal’s condition at the time of death (i.e.,

minimal autolytic alteration). Today, NMMTB

samples are archived as a major component of the

National Biomonitoring Specimen Bank at NIST

environmental chemistry facilities in Gaithersburg,

Maryland, and Charleston, South Carolina.

The DOC (NOAA and NIST) and DOI (FWS,

U.S. Geological Survey [USGS], and Minerals

Management Service [MMS]) have been involved in

collaborative research on and monitoring of Alaska

marine mammals for more than a decade. In 1986

NOAA and the MMS initiated the Alaska Marine

Mammal Tissue Archival Project (AMMTAP) to

address Alaska Native concerns about the effects of

various industrial proposals for the outer continental

shelf (e.g. oil and gas, offshore mining) on subsistence resources. By 1992 AMMTAP had become

an integral component of the MMHSRP specimen

banking effort, especially with respect to NOAA

trust resources in Alaska (Becker et al. 1993, Becker

et al. 1997). The creation of a Biological Resources

Division (BRD) within the USGS modified the

existing DOC-DOI relationship in AMMTAP to

provide greater scientific participation by DOI in

MMHSRP planning and research activities.

The BRD’s participation in the MMHSRP has

resulted in a longer list of indicator species that is

more representative of DOC and DOI responsibilities and information needs. Importantly, it has

brought additional biological and field and laboratory capability to Alaska efforts. The inclusion of

additional expertise in population and arctic ecology

is leading to novel approaches to delineate contaminant pathways. As an example, a special emphasis

by NMFS and BRD investigators will focus on

polar

bear–ice seal food chain interactions and contaminant transfers. The FWS’s Marine Mammal Management in Alaska, MMS, State of Alaska, and

several tribal entities (e.g., the North Slope Borough) work closely with the BRD and NOAA to set

AMMTAP priorities and assist with the collection

of biological materials from subsistence hunting.

The selection of DOC and DOI target species

and geographic areas of concern (Table 11) is based

on resource management needs and priorities. In

general, these include (1) access — available

source at a regular time and location; (2) representation of marine mammal species and U.S. ecosystems (e.g., pelagic vs. coastal); (3) potential contaminant bioaccumulation to levels of health concern;

(4) representative trophic level and transport pathways; and (5) human use and economic values (e.g.,

subsistence). The principal MMHSRP tissues for

archiving include liver, kidney, and blubber.

Rigorous sampling protocols, developed by NOAA

and NIST through the AMMTAP, are adhered to by

MMHSRP participants in the field (Becker et al.

1991). As the program evolves, new protocols are

being developed for blood collection and banking

with contaminant analyses in mind.

Since 1987 the AMMTAP and MMHSRP

programs have archived 1,173 tissue specimens

from 27 species and 391 individuals (Figure 9). On

a regional basis, this includes 72 cetaceans and 20

pinnipeds from the Atlantic Ocean; 17 cetaceans

Table 11. “Indicator Species” for the National Marine Mammal Tissue Bank

Species Region Habitat Source

Harbor Porpoise, Phocoena phocoena Northeast U.S. Coastal Incidental

Pacific U.S.
132

Dall’s Porpoise, Phocoenoides dalli Pacific U.S. Pelagic Incidental

Bottlenose Dolphin, Southeast U.S. Coastal Strandings

Tursiops truncatus including Gulf of Mexico

Atlantic White-sided Dolphin, Northeast U.S. Coastal & Pelagic Strandings

Lagenorhynchus acutus

Beluga Whale, Bering Sea Coastal Subsistence

Delphinapterus leucas and Arctic Ocean

Pilot Whales, Globicephala spp. Northeast U.S. Pelagic Strandings

Southeast U.S.,

including Gulf of Mexico

Bowhead Whale, Bering Sea Coastal Subsistence

Balaena mysticetus and Arctic Ocean

Harbor Seal, Phoca vitulina Northeast U.S. Coastal Incidental

Pacific U.S.

including Gulf of Alaska Subsistence

Ringed Seal, Phoca hispida Bering Sea Coastal Subsistence

and Arctic Ocean

Northern Fur Seal, Pacific U.S. Pelagic Subsistence

Callorhinus ursinus including Gulf of Alaska

California Sea Lion Pacific U.S. Coastal Strandings

Zalophus californianus Incidental

Polar Bear, Ursus maritimus Bering Sea Coastal & Subsistence

and Arctic Ocean Pelagic
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

133

from the Gulf of Mexico; 26 cetaceans, 33 pinnipeds, and 3 sea otters from the Pacific Ocean (including southeastern Alaska); and 76 cetaceans, 116

pinnipeds, and 28 fissipeds (sea otters and polar

bears combined) from the Arctic (includes Gulf of

Alaska, Bering Sea, and Arctic Ocean). Periodically, chemical analyses for specified contaminants

are conducted on a selection of NMMTB blubber

and liver samples. These analyses provide baseline

information to resource managers, in some instances

the only such information available. They also allow

NIST investigators to monitor tissue stability and

the effects of cryogenic storage. Importantly, they

also provide an analytical comparison for NWFSC

investigators.

In view of the high costs associated with the

collection and archiving of MMHSRP specimens,

and their increasing value with time, the MMHSRP

managers and major partners have formalized a

policy for access to samples. Access refers to the

availability of archived samples to the scientific

community and the contributor for environmental

baseline analyses. In brief, this policy addresses the

ownership and disposition of banked tissues, procedures for requesting banked samples including

scientific justification, review and approval processes, and analytical and data sharing requirements

(Wise and Koster 1995). To date, only a very

limited number of samples have been shared. In

every case, DOC and DOI information needs and

MMHSRP goals have been addressed by collaborative studies with shared resources (Table 12). 

Figure 9. Tissues in National Marine Mammal Tissue Bank, cumulative by year.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

134

Examples include contaminant, genetics, and proximate composition analyses performed on tissues

from beluga whales, ringed seals, polar bears, and

other marine mammals (e.g., HCHs, PCBs, and

DDT in northern fur seals [Moessner et al. 1992,

1994]; organoarsenic compounds in livers [Goessler

et al. 1998]; methyl mercury in belugas [Behlke et

al. 1996]). 

The NMMTB is not intended to preclude other

biomonitoring programs conducted independently.

The specimen bank functions as a research tool that

can complement existing efforts by preserving and

providing biological reference materials. In addition, analytical laboratories that participate regularly

in the MMHSRP are able to conduct quality analyses on reference or newly collected materials in

support of a program’s particular objectives.

Quality Assurance Program (QAP): One role of the

QAP is to ensure the accuracy, precision, level of

detection, and intercomparison of analytical data

resulting from analyses of MMHSRP samples

(Wise

1993). In this role, the QAP provides federal and

non-federal partner laboratories with biological

collection information, control materials, standard

reference materials, and interlaboratory comparisons

(Wise and Koster 1995, Becker et al. 1997). In

support of the MMHSRP's biomonitoring function,

 the NIST conducts the Marine Mammal

Table 12. Interlaboratory comparison exercises conducted for the Marine Mammal Health

and Stranding Response Program, 1991–1997

Dates Analytes Matrix Objective Participants

1991–92 PCBs whale blubber lab comparability NIST; NWC; DFO Canada;

Cl pesticides1 GERG; Univ. of Ulm

Elements whale liver CM2 analytical control NIST; NWC

1992–93 PCBs whale blubber; lab comparability NIST; DFO Canada;

Cl pesticides1 whale blubber CM2 Univ. of Ulm

1993–94 PCBs whale blubber; SRM development NIST; NWC; DFO Canada;

Cl pesticides1 whale blubber CM2 GERG; Arthur D. Little;

NW Aquatic Sciences;

Univ. of Ulm

1993–97 Elements whale & seal liver sample comparability NIST; NWC

PCBs whale & seal blubber

Cl pesticides1

Elements whale liver CM2 analytical control NIST; NWC

1997–98 Elements whale liver lab comparability & NIST; NWC;

control material Texas A&M Univ.

development 1

Chlorinated Pesticides 2

Control Material
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

135

Quality Assurance Project (MMQAP) for organic

and inorganic analyses. A primary focus is the

quality assurance associated with NMMTB samples.

The MMQAP is co-managed by NMFS and NIST.

NIST has developed blubber and liver control

materials and standard reference materials (blubber)

for interlaboratory comparisons. These materials

have become important resources for quality testing

by other analytical facilities in the United States and

elsewhere.

NIST conducts interlaboratory comparison

exercises among the analytical laboratories participating in the MMHSRP and other facilities engaged

in marine mammal studies on an annual basis.

Interlaboratory comparisons address techniques and

data quality and identify potential sources of procedural and measurement variability. All NMFSsponsored marine mammal studies with objectives

related to contaminants are required to participate in

the MMQAP. Blood serum protocols (i.e., procedures for collection and storage of serum) are being

developed that make quality assurance part of the

research.

In addition to the DOI's collaboration with the

MMHSRP, two bureaus within the DOI conduct

ecological research and monitoring to investigate

contaminant trends in marine mammals. Within its

management prerogative, the FWS may conduct

species-specific biomonitoring or site-specific

surveys through its Marine Mammal Management

and Ecological Services offices (e.g., polar bears;

Norstrom et al. 1998). FWS projects tend to be

issue-oriented surveys to establish baseline conditions, assess damage, and develop mitigative or

preventive measures. For example, the FWS’s

Environmental Contaminants Program explores

wildlife contaminant issues and threats at more than

75 locations nationwide (see www/http:/fws.gov).

These efforts have provided important baseline data

and, in several instances, highlighted the need for

additional species- or habitat-related studies. To

illustrate, cadmium concentrations in kidney tissues

of Pacific walruses from the Bering and Chukchi

Seas were reported to be high (147 to 204 ug/g dw;

Warburton and Seagars 1993). The levels were

high enough to raise concerns about animal health

and about cadmium sources and pathways. These

concerns are topics of current BRD research in

Alaska.

A primary FWS mission is to maintain the health

and stability of the marine ecosystems and populations for which it is entrusted. A major thrust of

FWS research and surveys has been to delineate

important habitats and migratory pathways and to

determine the status and trends of managed populations. With respect to marine mammals, the most

extensive contaminant surveys have targeted Pacific

walruses and polar bears in the Bering, Chukchi,

and Beaufort Seas and sea otters along the west

coast and Alaska. In Alaska, the FWS shares its

data with public health organizations. It has also

provided tissue samples for archiving through the

AMMTAP. With respect to the MMHSRP national

goals, the DOI needs to focus more attention on

manatees in Florida and the Caribbean Sea.

The USGS’s BRD is the responsible scientific

entity for biological research on marine mammals

within the DOI. The BRD conducts a variety of

research projects to meet the need for information

on marine mammal populations, habitats, and

ecosystems of concern. The development of scientifically reliable methods to enumerate populations

and stocks, describe seasonal habitat use, and assess

environmental impacts are major program areas.

Thus, BRD research projects tend to be populationoriented and often last 3 to 5 years. Longer-term

goals of BRD marine mammal research are to

improve understanding of ecological relationships

and the effects of environmental change. BRD

studies generally are not directed contaminant

studies, per se. One exception is the division's

participation in the MMHSRP through the

AMMTAP. Another is a study of sea otters

throughout their North American range (e.g., Estes

et al. 1997). Special research emphasis has focused

on the effects of the Exxon Valdez oil spill on sea

otters in south-central Alaska. In particular, nearshore predator-prey relationships and population

recovery have been investigated. Continuing efforts

to assess radionuclide contaminant levels in polar

bears involve international coordination with circumpolar nations.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

136

In addition to DOI and DOC contaminant studies, the EPA has performed chemical analyses on

tissues from marine mammals and other marine

organisms in support of specific studies or at specific sites. As an example, the EPA participated in

the investigation of die-offs of bottlenose dolphins

along the U.S. Atlantic coast in 1987 and 1988. It

also conducted several related follow-up studies of

Atlantic bottlenose dolphins. The EPA is presently

administering several subsistence-oriented studies

in Alaska, through the University of Alaska, which

involve marine mammal contaminant analyses and

database development.

Non-governmental and International Studies

Numerous non-governmental and international

organizations have funded, are currently funding, or

are planning relevant contaminants research on

marine mammal populations of interest to U.S.

management and tribal authorities. Most noteworthy

of these are the Arctic Monitoring and Assessment

Program (AMAP), the International Whaling Commission (IWC), the United Nations Environment

Programme, the North Slope Borough Wildlife

Department, and the World Wildlife Fund International. The AMAP, a circumpolar program, was

established under the Arctic Environmental Protection Strategy in the early 1990s and is a continuing

effort under the Arctic Council (AMAP 1998). The

AMAP plan for 1998-2002 includes marine mammal contaminant monitoring (persistent organic

pollutants, petroleum hydrocarbons, heavy metals,

and trace elements) in key indicator species including polar bears, ringed seals, and beluga whales.

The IWC considers potential pollutant effects

relevant to the management of cetacean populations.

An IWC-sponsored workshop was held in 1995 to

assess contaminant effects (Reijnders et al. 1999).

This workshop concluded that multidisciplinary and

multinational research planning and execution are

needed to understand the impacts of contaminants

on marine mammal populations. Tribal governments, such as the North Slope Borough, are conducting biological research and monitoring contaminants and, in Alaska, work in close association with

AMMTAP and MMHSRP investigators. Tribal

concerns are focused primarily on the health of

wildlife populations hunted for subsistence and on

the potential risks to indigenous people from consuming marine mammal products (e.g., cadmium in

beluga whales) and from other changes in rural

communities. A major concern of Alaska natives is

that traditional knowledge be incorporated in future

scientific planning. Finally, within the United

States, many universities and national and international foundations and organizations have established cooperative research programs and sponsored

directed research to answer specific questions about

contaminant pathways, processes, and probable

effects on marine mammals. 

Conclusion

A common focus of many research and monitoring

programs has been to determine baseline levels of

heavy metals and persistent organic pollutants in

marine mammal populations. Few programs have

adequately addressed issues of experimental or

study design. These issues must be addressed,

however, for information on contaminant trends and

effects to be scientifically defensible. For example,

quality assurance and quality control are most

frequently addressed at the laboratory or study level.

The lack of standardization in field and laboratory

approaches has resulted in numerous problems with

comparability and repeatability — essential ingredients of quality science. Similarly, few studies have

incorporated a health perspective. Other problems

that arise particularly in monitoring efforts, such as

sample size, frequency, and intervals, require pilot

research and must be addressed with practical

(logistics and cost) and statistical objectives in mind

(e.g., Jensen and Cheng 1987, Bignert et al. 1993).

As federal and state agencies attempt to make the

concept of ecosystem management operational,

there is a growing need for coordination of research, monitoring, and quality-control programs at

regional, national, and international scales. The

coordination among NOAA, NIST, and the USGS

through their respective roles in MMHSRP,

NMMTB-AMMTAP, and AMAP provides an

example. By working together, and with others,

these agencies are engaged in efforts to conserve

valued species, ensure ecosystem health, and protect
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

137

rural lifestyles. Coordination, synthesis, and crossfertilization of multidisciplinary interests are essential. The integrated assessment approach requires

that a large cross-section of the scientific community shares data and information and works cooperatively to produce a synthesis. This synthesis combines information on contaminants, the status and

trends of marine mammal populations, population

biology and ecology, and animal health.

References

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Department of Commerce, NOAA Technical

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Becker, P. R., S. A. Wise, L. K. Thorsteinson, B. J.

Koster, and T. Rowles. 1997. Specimen banking of

marine organisms in the United States: current status

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334:1889–1906.

Becker, P. R., S. A. Wise, B. J. Koster, and R. Zeisler.

1991. Alaska Marine Mammal Tissue Archival

Project: revised collection protocol. U.S. Department

of Commerce, NIST, NISTIR 4529. 33 pp.

Behlke, M. K., P. C. Uden, M. M. Schantz, and S. W.

Wise. 1996. Development, validation, and

application of a method for quantification of methylmercury in biological marine materials using gas

chromatography atomic emission detection.

Analytical Chemistry 68:3859–3866.

Bignert, A., A. Gothberg, S. Jensen, A. Klitzen, T.

Odsjo, M. Olsson, and L. Reutergardh. 1993. The

need for adequate biological sampling in ecotoxicological investigations: a retrospective study of 20

years pollution monitoring. The Science of the Total

Environment 128:121–139.

Department of Commerce. 1998. Marine Mammal

Protection Act Annual Report. January 1, 1997 to

December 31, 1997. National Marine Fisheries

Service, Silver Spring, MD 20910. 141 pp.

Department of the Interior. 1997. Administration of the

Marine Mammal Protection Act of 1972. Annual

Report, January 1, 1995 to December 31, 1995. U.S.

Fish and Wildlife Service and U.S. Geological

Survey/Biological Resources Division, Washington,

D.C. 20240. 35 pp.

Dierauf, L. A. 1994. Pinniped forensic, necropsy and

tissue collection guide. U.S. Department of

Commerce, NOAA Technical Memorandum, NMFSOPR-94-3. 80 pp.

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Alaska: risks in perspective. State of Alaska

Epidemiology Bulletin, Vol. 2 (No. 1). 140 pp.

Estes, J. A., C. E. Bacon, W. M. Jarman, R. J. Norstrom,

and R. J. Anthony. 1997. Organochlorines in sea

otters and bald eagles from the Aleutian Archipelago.

Marine Pollution Bulletin 34:486–490.

Goessler, W., A. Rudorfer, E. A. Mackey, P. R. Becker,

and K. J. Irgolic. 1998. Determination of arsenic

compounds in marine mammals with high

performance liquid chromatography and inductively

coupled plasma mass spectrometry as element specific

detector. Applied Organometallic Chemistry

12:491–501.

Jensen, A., and Z. Cheng. 1987. Statistical analysis of

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1:230–238.

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of Standards Special Publication 740.

Moessner, S. I., I. S. Barudio, T. S. Spraker, G. Antonellis, G. Early, J. R. Geraci, P. R. Becker, and K.

Ballschmiter. 1994. Determination of HCHs, PCBs,

and DDTs in brain tissues of marine mammals of

different age. Fresenius’ Journal of Analytical

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WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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Appendix D:

Prevalence of Lesions Associated with a Disease Complex in the

Baltic Gray Seal (Halichoerus grypus) during 1977–1996

Anders Bergman

Veterinary Pathologist

Contaminant Research Group, Swedish Museum of Natural History

P.O. Box 50 007

S-104 05 Stockolm, Sweden

and

Department of Pathology, Faculty of Veterinary Medicine

Swedish University of Agricultural Sciences

P.O. Box 7028

750 07 Uppsala, Sweden

Introduction and Summary

The investigation was initiated due to a serious

reduction of the Baltic gray and ringed seal

populations. Earlier, impaired reproductive ability

had been reported, with occlusions and stenoses of

the uterus in the two species as well as a high

frequency of uterine smooth muscle cell tumours

(leiomyomas). The lesions of the female sex organs

were found to be part of a disease complex in adults

of both sexes of these species. Besides lesions of

the uterus, the disease complex comprises lesions of

1. Integument, especially claws;

2. Skull bones, especially masticatory bones;

3. Intestine (colonic ulcers);

4. Kidneys (glomerulopathy, tubular cell

proliferations);

5. Arteries (sclerosis); and

6. Adrenals (cortical hyperplasia, cortical

adenomas).

Here I focus on the results of a time-trend study

of the two decades 1977–1986 and 1987–1996

(Bergman 1999). During 1977–1996, necropsies

were performed on 159 Baltic gray seals.The

animals were grouped by sex and the following age

classes: subadults 1–3 years old and adults 4–15,

16–25, and >25 years old. Seals 4 years and older

were considered sexually mature. Regarding upper

age limits, some females were around 40, and the

oldest male was 25 years old. A semi-quantitative

evaluation was made of the degree and extent of

lesions in the non-reproductive organs, using the

following scale: no change apparent (0), slight (1),

moderate (2), severe (3), and fatal (4).

Prevalences (%) were compared between the

two decades in “moderate” to “severe” lesions of

claws, intestine, arteries, and adrenals. Similar

comparisons were made for lesions of the female

reproductive organs and rates of pregnancy. Using

the same material, animals born before 1980 were

compared with those born after 1979 to investigate

a possible relationship between seal health and the

evident decrease of PCB and DDT pollution of the

Baltic during the 1970s.

In summary, there was a positive trend in

gynecological health over time, with a decrease

from 42% to 11% in the prevalence of uterine

obstructions, and an increase from 9% to 60% in

pregnancies. The incidence of uterine tumors

(leiomyomas) seems to have decreased slowly, from

53% to 43% between the two decades.

Of special interest is that the prevalence of

colonic ulcers has tended to increase in young gray
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

140

seals. This finding indicates that their food may

contain “new” (previously unidentified) toxins or

increased amounts of “old” ones, affecting the

seals’ immune system.

Favorable Tendencies

Some important favorable tendencies were noted

with regard to the lesions examined (Bergman

1999). In particular, the changes in the prevalence

of uterine obstructions and the rate of pregnancy

were statistically confirmed, while the change in the

incidence of leiomyomas was not. A slight

improvement was also found in the incidence of

adrenocortical hyperplasia, but it was not

statistically significant. A reduced incidence of

bone lesions has also been found (Bergman et al., in

prep.). Arteriosclerotic lesions were strongly

correlated with increasing age, but no difference in

prevalence was discerned between the two periods

(Bergman 1999). The apparently favorable

tendencies are probably related to the decreases of

DDT and PCBs in Baltic biota recorded during the

1970s (Olsson and Reutergård 1986, Bignert et

al.1995).

As discussed in previous and forthcoming

reports on ringed seals (e.g., Helle 1980 a,b;

Bergman et al., in prep.) and gray seals (Bergman

and Olsson 1985) of the Baltic, uterine occlusions

and stenoses are related to pregnancy. Some cases

have shown retained fetal membranes containing

fetuses, aligned to stenosed parts of the horns. The

obstructions probably develop secondarily as a

result of interrupted pregnancies (Bergman and

Olsson 1985). The lesions may be associated with

hormonal imbalance and immune suppression,

probably due to interference of organochlorines

with steroid metabolism. The lesions may also

result from a disturbed post-parturient puerperium,

or from fetal death due to the influence of

organochlorines (Bergman et al., in prep.).

The prevalence of uterine leiomyomas in gray

seals seems to have been very high in both

collection periods. According to Kennedy and

Miller (1993), leiomyoma is a common tumor of the

female tubular genitalia in the dog, but it is

uncommon in other domestic species. It rarely

occurs in female dog genitalia before middle age

and is often associated with ovarian follicular cysts

or estrogen-secreting tumors, endometrial and

mammary hyperplasia, and mammary neoplasia.

When bitches are castrated early in life, leiomyomas

do not develop. If leiomyomas are already present,

they regress following castration. These

circumstances implicate a background of endocrine

disorder as being linked to the development of

leiomyomas.

Uterine leiomyoma is a common tumor in

humans. It affects 20 to 25% of women during their

reproductive years. There is strong evidence that

the growth of leiomyomas is estrogen-dependent;

they generally regress after the menopause (Cotran

et al.1989). The clinical use in women of

gonadotropin-releasing hormone agonists has

improved knowledge about the nature of

leiomyoma. Treatments are intended to reduce

circulating levels of uterine tissue hormones,

particularly estradiol (Ueki et al.1995), resulting in

reduced leiomyoma size,

The continued high incidence of uterine

leiomyoma in Baltic seals is a matter of concern.

This tumor’s “natural” frequency of occurrence in

the seal populations is unknown. There is reason to

believe, however, that the high prevalence observed

in gray seals is due to the influence of one or more

factors in the environment which cause hyperestrogenic states. This belief is supported by the

results of examining large samples of kidney tissue

from Baltic seals with light microscopy (Bergman et

al. 1999) and electron microscopy (Bergman and

Bergstrand, in prep.). Besides the presence of

glomerular lesions, a high frequency and degree of

tubular-cell proliferations were observed in these

investigations. These observations indicate a

background of hormonal disturbance, probably

excess estrogen. Renal tubular-cell proliferations,

with the character of squamous metaplasia and with

localization similar to that found in the Baltic seals,

have been described in a male dog with Sertoli-cell

tumors in the testes and feminization (Lindberg et

al.1976) and in a bitch with an ovarian granulosacell tumor (Wouda et al. 1978).
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

141

Unfavorable Tendencies

Seals 4 to 15 years old born after 1979 had a higher

incidence of lesions in their digits and claws than

this same age class born before 1980, but this

difference was not statistically significant. Of more

consequence, however, is the evidently increasing

prevalence of colonic ulcers, which are often fatal.

This increase was statistically significant for young

animals (1 to 3 years old). Colonic ulcers in Baltic

seals seem to be associated with hookworm

(Corynosoma sp.) infection, which is suspected to

initiate the primary lesion of the intestinal mucous

membrane (Bergman and Olsson 1985). Compared

to the findings in Baltic gray seals, British grey

seals have a much lower incidence of intestinal

lesions in combination with Corynosoma sp.

infection. Baker (1980) examined two juvenile and

two adult British gray seals and found ulceration of

the ileum in just one animal, an 18-year-old female

heavily infested with Corynosoma sp. In a survey

of pathology in 34 juvenile and 12 adult British gray

seals, Baker (1987) reported that 81% of the animals

were infested with Corynosoma sp., but all of them

lacked signs of intestinal ulcers. Judging by the

literature, Baker (1987) concluded that Corynosoma

sp. usually do not cause gross intestinal changes in

seals.

Apart from drowning in fishing gear (72%),

severe colonic ulcers, with perforation of the

intestinal wall, was the most common cause of death

(7%) for gray seals in the Baltic. Fatal colonic

ulcers seem to most seriously afflict middle-aged

and aged males (16 to 25 years old). Such ulcers

were found in three out of six animals in this age

group, all of them collected between 1987 and 1996.

The increasing prevalence of colonic ulcers in

young Baltic seals indicates an increasingly

compromised immune system during recent years.

In recent Dutch experiments, when groups of

captive harbor seals (Phoca vitulina) were fed Baltic

or Atlantic herring, suppression of various cellular

and antibody responses of the immune system was

observed in the seals fed the Baltic herring (De

Swart et al. 1994, 1995; Ross et al. 1995, 1996).

These findings indicate that the food available to

Baltic seals is still sufficiently contaminated to

affect health. The fact that the incidence of colonic

ulcers has continued to increase in Baltic seals,

despite the reduced concentrations of known

organochlorines, might indicate that prey resources

contain hitherto-unidentified toxic contaminants, or

at least increased amounts of such contaminants.

Several industrial contaminants have been detected

recently that were previously not known to be

present in Baltic biota, including seals. These

include polybrominated diphenyl ethers (PBDE)

(Sellström et al. 1993), used as flame retardants in

polymeric materials, and bis (4-chlorophenyl)

sulfone (BCPS) (Olsson and Bergman 1995), a

compound used in the production of hightemperature polymers. Little is known about the

ecotoxicological effects of these compounds. 

Autopsies of Baltic seals indicate that the

endocrine system has been compromised in some

way, with probable involvement of the

hypothalamic-pituitary-gonadal and adrenal axis

(Bergman and Olsson 1985). Strong uptake of

PCBs in corpora lutea, adrenal cortex, and the

pituitary has been demonstrated in mice by using

whole-body autoradiography (Brandt 1975).

Accumulation of certain PCB congeners in the

pituitary and/or hypothalamus may lead to effects

on gonadotropin release and gonadal function. The

ability of PCBs to influence pituitary function has

been demonstrated experimentally. When studying

the effect of Aroclor 1242, a commercial PCB

product, on cultured anterior pituitary cells from

female immature rats, Jansen et al. (1993) found that

these cells exhibited increased gonadotropin

responses.

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P. J. H. Reijnders, and A. D. M. E. Osterhaus. 1994.

Impairment of immune function in harbour seals

(Phoca vitulina) feeding on fish from polluted

waters. Ambio 23:155–159.

De Swart, R. L., P. S. Ross, H. H. Timmerman, H. W.

Vos, P. J. H. Reijnders, J. G. Vos, and A. D. M. E.

Osterhaus. 1995. Impaired cellular immune

response in harbour seals (Phoca vitulina) fed

environmentally contamined herring. Clinical and

Experimental Immunology 101:480–486. 

Helle, E. 1980a. Reproduction, size and structure of the

Baltic ringed seal population of the Bothnian Bay.

Acta Universitatis Ouluensis, Series A, No. 106,

Biol. 11:1–47.

Helle, E. 1980b. Lowered reproductive capacity in

female ringed seals (Pusa hispida) in the Bothnian

Bay, northern Baltic Sea, with special reference to

uterine occlusions. Annales Zoologici Fennici

17:147–158.

Jansen, H. T., P. S. Cooke, J. Porcelli, T. C. Liu, and

L.G. Hansen. 1993. Estrogenic and antiestrogenic

actions of PCBs in the female rat: in vitro and in

vivo studies. Reproductive Toxicology 7:237–248.

Kennedy, P.C., and R. B. Miller. 1993. The female

genital system. Pages 349–470 in K. F. V. Jubb, P.

C. Kennedy, and N. Palmer (eds.), Pathology of

Domestic Animals, 4th ed., Vol. 3. Academic Press,

San Diego.

Lindberg, R., O. J. Jonsson, and H. Kasström. 1976.

Sertoli cell tumours associated with feminization,

prostatitis and squamous metaplasia of the renal

tubular epithelium in a dog. Journal of Small

Animal Practice 17:451–458.

Olsson, A., and Å Bergman. 1995. A new persistent

contaminant detected in Baltic wildlife: Bis(4-

chlorophenyl)sulfone. Ambio 24:119–123.

Olsson, M., and L. Reutergård. 1986. DDT and PCB

pollution trends in the Swedish aquatic environment.

Ambio 15:103–109.

Ross, P. S., R. L. De Swart, P. J. H. Reijnders, H. van

Loveren, J. G. Vos, and A. D. M. E. Osterhaus.

1995. Contaminant-related suppression of delayedtype hypersensitivity and antibody responses in

harbour seals fed herring from the Baltic Sea.

Environmental Health Perspectives 103:162–167.

Ross, P. S., R. L. De Swart, H. H. Timmerman, P. J. H.

Reijnders, J. G. Vos, H. van Loveren, and A. D. M.

E. Osterhaus. 1996. Suppression of natural killer

cell activity in harbour seals (Phoca vitulina) fed

Baltic Sea herring. Aquatic Toxicology 34:71–84.

Sellström, U., B. Jansson, A. Kierkegaard, and C. de Wit.

1993. Polybrominated diphenyl ethers (PBDE) in

biological samples from the Swedish environment.

Chemosphere 26:1703–1718.

Ueki, M., Y. Okamoto, T. Tsurunaga, Y. Seiki, M. Ueda,

and O. Sugimoto. 1995. Endocrinological and

histological changes after treatment of uterine

leiomyomas with danazol or buserelin. Journal of

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Wouda, W., E. Gruys, and T. A. M. Elsinghorst. 1978.

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a dog with a granulosa cell tumour. Zentralbl.

Veterinärmed.1. (A) 25:499–502.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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Appendix E:

What Experiments Might Have Told Us 

PART ONE OF A DIALOGUE

Robert W. Risebrough, Ph.D.

Research Ecologist

2711 Piedmont Avenue

Berkeley, CA 94705

The Workshop on Marine Mammals and Persistent

Ocean Contaminants has provided an opportunity to

review what we now know about the impacts of

synthetic organic contaminants on individual marine

mammals and on marine mammal populations. It

was gratifying to learn that the population of harbor

seals in the North Sea has recovered and that the

situation of seals in the Baltic appears to have

improved in a number of respects. Globally, with

the possible exception of the belugas of the St.

Lawrence River, no marine mammal population

appears now to be threatened by contaminants1

, and

organic contaminant levels in marine ecosystems

appear to have stabilized, or to be changing only

very slowly. 

Yet there are suggestions of continuing problems in the form of a continuing high incidence of

uterine smooth muscle cell tumors and an increase

in colon ulcers in gray seals in the Baltic, at a time

when concentrations of the “conventional” pollutants have declined. In the 1960s, the Baltic Sea

provided many of the “early warnings” of contaminant effects on natural ecosystems. It is certain that

human populations will continue to expand through

at least the next century, and that their chemical

technologies will continue to expand indefinitely.

Some effects of new chemical technologies on

humankind and our fellow species cannot be predicted at this time.

 What, however, have we learned from the past

that might provide some guidance in developing

conservation strategies for the protection of marine

mammals from any effects of synthetic chemicals in

the future? 

Thirty years ago, a number of bird populations

were in serious decline; the peregrine falcon was

almost extinct as a breeding species in the lower 48

of the United States. In 1968 and 1969, the Wisconsin Department of Natural Resources conducted

hearings to determine whether the continuing use of

DDT was in violation of a state law that prohibited

the use of any substance that, in consequence of its

use, entered the waters of the state and harmed fish

or wildlife. I was there, both as a scientific witness

and as an advisor to the Environmental Defense

Fund. 

Eggshell thinning was a symptom common to

all of the species undergoing population declines.

Joseph Hickey and Daniel Anderson of the University of Wisconsin had just demonstrated that herring gull eggs with higher amounts of the DDT

metabolite DDE had thinner shells than eggs with

lower amounts of DDE. But the eggs with higher

amounts of DDE also had higher concentrations of

several other pesticides and higher concentrations of

the PCBs. It was impossible to tell which one of

them was actually responsible for the eggshell

thinning. The pesticide industry stressed that there

was no compelling evidence that DDE was the

cause of the problem.

1

Editors’ note: Some marine mammal populations that

inhabit extremely polluted waters (e.g., river dolphins,

finless porpoises, and coastal marine dolphins in parts of

Asia) have not been studied as intensively as belugas in

the St. Lawrence, and the role of contaminants in their

declines has not been adequately assessed.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

144

The most dramatic moment during the hearings

was probably the testimony of Dr. Lucille F.

Stickel, Director of the U.S. Fish and Wildlife

Service’s Patuxent Wildlife Research Center. She

presented the results of a controlled experiment that

showed that ducks on a diet containing DDE laid

thin-shelled eggs. The DDE content of the food was

comparable to DDE concentrations found in the

environment, and DDE concentrations in the eggs

were similar to those in the thin-shelled eggs of wild

birds. Immediately, we had a winning case in

Wisconsin; in the hearings held shortly afterward in

Washington, DC, by the newly formed EPA to

consider whether the use of DDT should continue or

end at the national level, these experimental data

provided critical support for the testimony on shell

thinning of eggs of the brown pelican, bald eagle,

and peregrine falcon. Follow-up experiments

confirmed that the other pesticides and the PCBs

had not contributed to the thinning.

Wildlife benefited enormously from the decisions to end DDT use in the USA; without the

scientifically sound, scientifically clean experimental results, the outcome could have been very different. The bald eagles would surely have followed

the peregrines into extinction as breeding species in

the lower 48 states, and high rates of reproductive

failure of fish-eating birds would have continued. 

We still do not understand exactly how DDE

thins eggshells. In some species, at least, the number of organic sites at which shell crystallization

starts is lower in birds with higher levels of DDE

contamination; DDE may therefore block a receptor

involved in shell synthesis. Understanding the

molecular mechanisms of eggshell thinning, however, is no longer a conservation priority for the

species of birds that were affected. Moreover, the

physiology of falcons and pelicans is different from

that of marine mammals, and also from the physiology of those families of birds in which DDE does

not produce shell thinning. But any increase in our

understanding of how DDE causes shell thinning in

even a few species would provide insight into

possible modes of action of other synthetic organic

contaminants in other biological systems. Follow-up research on the mechanisms of shell thinning would therefore be worthwhile.

In the early 1970s, I was privileged to work

with Bob DeLong, Bill Gilmartin, John Martin, and

a number of other colleagues in an attempt to

determine the cause of the high incidence of premature births in California sea lions. Females giving

birth prematurely had higher concentrations of DDE

and PCBs than females with normal births, suggesting a cause-effect relationship. But there were other

differences between the two groups. The females

giving birth prematurely were younger and had

contaminant profiles typical of the Southern California Bight; older females had contaminant profiles

typical of central California to the north. Disease

vectors endemic in the population were known to

cause reproductive disorders, although of a different

nature. Under the El Niño conditions of 1997–199

8, with a much-reduced food supply, there was an

increase in the incidence of premature births, indicating that nutrition was a probable factor, and that

it could also have been a factor in the earlier cases.

Do DDE, PCBs, a combination of DDE and

PCBs, or a combination of these with other contaminants contribute to the premature births? No one

knows. Because the California sea lion population

increased substantially in southern California, this

question no longer has a conservation priority. But

a scientifically sound answer would be immensely

valuable in assessing the potential risk of future

contaminants to marine mammals, other wildlife

species, and humans. Again, any increase in our

understanding of the molecular mechanisms whereby synthetic chemicals interact with biological

systems is of potential benefit in developing conservation strategies.

The political climate of the early 1970s (and

even more so in recent times) was unfavorable to

the temporary captivity of any marine mammal for

research purposes, even if undertaken for the long-te

rm benefit of the species. Surely it is essential to

know what factor or factors are harming a marine

mammal population. There was not and there has

not been, however, any kind of dialogue and communication among all groups and individuals

interested in the welfare of the sea lions and other
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

145

species of marine mammals. If there had been, it is

likely that an acceptable protocol would have been

drawn up and implemented. Two comparable

groups of sea lions, one fed wild-caught fish from

the coastal waters near Los Angeles with higher

DDE levels, the other fed fish from central California with lower DDE levels, could have been followed through the pregnancy cycle to answer the

key question of whether DDE was contributing to

the premature births. If it was, the knowledge

gained would have been beneficial; if not, other

causes, particularly one or more disease vectors,

could have been looked for and the study might

have provided some clues.

The population of harbor seals in the western

portion of the Dutch Wadden Sea dropped sharply

between 1960 and 1975 as a result of a decrease in

the production of young. Dr. Peter Reijnders fed a

captive group of 12 female seals fish from an area

of the North Sea that received waters from the river

Rhine River; another group of 12 seals was fed less

contaminated fish from the Atlantic Ocean. Reproduction was significantly reduced in the group fed

the more contaminated fish.

Chemical analyses indicated that PCB concentrations were significantly higher in the North Sea

fish, suggesting that PCBs were the probable cause.

This was sufficient to persuade the government of

The Netherlands to support a European Community

ban on the production and use of PCBs. PCB

contamination in the area subsequently declined and

the harbor seals have recovered. But like the eggs

of herring gulls in Lake Michigan, the fish from the

North Sea contained a complex soup of chemical

contaminants, some of which might not be detectable by analytical methodologies current then or

now. A chemical or group of chemicals that covari

ed with the PCBs could have been the real cause of

the reproductive failures. As in the United States,

the political climate was unfavorable to what might

be perceived as an experiment with marine mammals that involved toxic compounds, even if the

amounts of the toxic compounds were equivalent to

those in fish consumed by both people and wildlife.

If, however, a third group of harbor seals had been

fed fish containing an equivalent amount of PCBs,

without the other components of the soup, the

results would have been much more definitive. If

the PCB group had not shown the depressed reproduction, one or more of the other contaminants must

have been responsible. An effort to track them

down would be the next immediate conservation

priority.

Many environmentalists are not aware that the

final decision to ban DDT in the United States was

not based primarily on its effects on pelicans and

peregrine falcons but on its potential harm to human

health; this concern, however, was based largely on

the results of the wildlife studies. Nevertheless, the

end result was the same; the peregrines have returned. Next to, or with DDT, the highly toxic

organochlorine pesticide dieldrin has probably been

the most detrimental to wildlife. Millions of birds

have been killed by dieldrin. For our participation

in the hearings that addressed the question of wheth

er the use of dieldrin should end, we analyzed

samples of mothers’ milk; a friend came with her

infant daughter and sat in a conspicuous place to

ensure eye contact with the judge. If the argument

that dieldrin was harmful to human health would

stop the killing of bald eagles and egrets, let that be

the argument. Wildlife will benefit. Similarly, an

argument that a proposed experiment will benefit

humans should not be rejected out-of-hand by an

environmentalist more concerned with the welfare

of wildlife. Interests frequently overlap and sometimes even coincide.

If more people see the broader picture the next

time a proposal is made to use captive marine

mammals to address a conservation-related problem,

the proposal is much more likely to be approved.

But communication and dialogue are critical.

During the exciting days of the DDT hearings, when

I depleted my own lifetime supply of adrenaline,

there was a very close collaboration between the

environmental groups and the environmental scientists. Now, there is frequently little or no communication. A greater appreciation of scientific considerations by environmentalists and a greater effort by

environmental scientists to provide information

could only benefit the cause to which both groups

are dedicated.
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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Appendix F:

Abbreviations and Acronyms Used in This Report

Abbreviations for Chemical Names, Physiological Terms, and Related Items

ACHE acetylcholinesterase

ACTH adrenocorticotropic hormone

Ah arylhydrocarbon

AR androgen receptor

BPA bisphenol A

BCPS (bis (4-chlorophenyl) sulfone), a compound used in the production of polymers

CYP1A subfamily of monoxygenases

DAS delayed anovulatory syndrome

DBCP (dibromochloropropane), a fungicide

DDT (22,-bis-(p-chlorophenyl)-1,1-trichloroethane), a widely used organochlorine

pesticide

DDTs the sum of concentrations or amounts of DDT and all its isomers and metabolites

DDT the sum of concentrations or amounts of DDT and all its isomers and metabolites

DDD (2,2,-bis-(p-chlorophenyl)-1,1-dichloroethane), metabolite of DDT

DDE (2,2,-bis-(p-chlorophenyl)-1,1-dichloroethylene), metabolite of DDT

EROD (7-ethoxyresorufin o-deethylase), a mixed function oxidase

FSH follicle stimulating hormone

GH growth hormone

HCG human chorionic gonadotropin

DES diethylstilbestrol

DHT dihydrotestosterone

DNA deoxyribonucleic acid

EDCs endocrine disrupting compounds

FSH follicle stimulating hormone

GnRH gonadotropic releasing hormone

HAHs halogenated aromatic hydrocarbons

HCHs hexachlorocyclohexanes

HgCL2 mercuric chloride

LH luteinizing hormone

MT metallothionein 

NK natural killer cell

OP organophosphate 

P450 (cytochrome P450), a family of monooxygenase enzymes that are induced by certain

toxic substances. The name is based on an absorption spectrum of 450 nm.

PACs polycyclic aromatic compounds

PAHs polycyclic aromatic hydrocarbons

PBDE polybrominated diphenyl ethers

PBPK physiologically based pharmacokinetic models

PCBs polychlorinated biphenyls

PCB-MSFs polychlorinated biphenyl methyl sulfones

PCDDs polychlorinated dibenzo-p-dioxins

PCDFs polychlorinated dibenzofurans
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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PCNs polychlorinated napthalenes

PFC plaque-forming cells

POPs persistent organic pollutants

PROD (pentoxyresorufin o-depentylase), a mixed function oxidase

PTBS persistent, toxic, and bioaccumulative substances 

PVC polyvinyl chloride

QA quality assurance

QC quality control

SCID Severe Combined Immune Deficient

SRMs standard reference materials

TBT tributyltin

TCDD 2,3,7,8-tetrachlorodibenzo-p-dioxin

TEF toxic equivalency factor

TEQs toxic equivalents

TSH thyroid stimulating hormone 

TTR transthyretin

Acronyms for Organizations, Agencies and Programs

AMAP Arctic Monitoring and Assessment Program

AMMTAP Alaska Marine Mammal Tissue Archival Project

BRD Biological Resources Division, U.S. Geological Survey

CDC Centers for Disease Control and Prevention, U.S. Department of Health and Human

Services

DOC Department of Commerce

DOI Department of the Interior

EPA U.S. Environmental Protection Agency

IPCS International Program on Chemical Safety

IWC International Whaling Commission

MMHSRP Marine Mammal Health and Stranding Response Program

MMPA U.S. Marine Mammal Protection Act of 1972

MMS Minerals Management Service

NIST National Institute of Standards and Technology

NMFS National Marine Fisheries Service

NMMTB National Marine Mammal Tissue Bank

NOAA National Oceanic and Atmospheric Administration

NWFSC Northwest Fisheries Science Center, National Marine Fisheries Service

OECD Organization for Economic Cooperation and Development.

UNEP United Nations Environment Programme

USFWS U.S. Fish and Wildlife Service

USGS U.S. Geological Survey
WORKSHOP ON MARINE MAMMALS AND PERSISTENT OCEAN CONTAMINANTS

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Appendix G:

Common and Scientific Names of Vertebrate Animals

Used in This Report

Amazon River dolphin Inia geoffrensis

Anchovy Engraulis mordax

Bald eagle Haliaeetus leucocephalus

Beluga (whale) Delphinapterus leucas

Bottlenose dolphin Tursiops truncatus

Bowhead whale Balaena mysticetus

California sea lion Zalophus californianus

Common dolphin Delphinus spp.

Dall’s porpoise Phocoenoides dalli

Dover sole Microstomus pacificus

Dugong Dugong dugon

Elephant seals Mirounga spp.

Fin whale Balaenoptera physalus

Florida manatee Trichechus manatus latirostris

Gray seal Halichoerus grypus

Gray whale Eschrichtius robustus

Hake Merluccius spp.

Harbor seal Phoca vitulina

Harbor porpoise Phocoena phocoena

Humpback whale Megaptera novaeangliae

Killer whale Orcinus orca

Long-finned pilot whale Globicephala melas

Marine otter Lutra felina

Mink Mustela vison

Minke whale Balaenoptera acutorostrata

Northern elephant seal Mirounga angustirostris

Northern fur seal Callorhinus ursinus

Northern right whale Eubalaena glacialis

Northern (Steller’s) sea lion Eumetopias jubatus

Peregrine falcon Falco peregrinus

Polar bear Ursus maritimus

Ringed seal Phoca hispida

Rockfish Sebastes spp.

Rough-toothed dolphin Steno bredanensis

Sardine Family Clupeidae

Sea otter Enhydra lutris

Southern (California)

 sea otter Enhydra lutris nereis

Sperm whale Physeter macrocephalus

Striped dolphin Stenella coeruleoalba

Walrus Odobenus rosmarus

Weddell seal Leptonychotes weddellii

West Indian manatee Trichechus manatus

Brown pelican Pelecanus occidentalis

Hamster Mesocricetus auratus

Herring gull Larus argentatus

Rhesus monkey Macaca mulatta

White croaker Genyonemus lineatus