The Foundation for Global Action on 


Persistent Organic Pollutants: 


A United States Perspective 


Office of Research and Development 

Washington, DC 20460 

EPA/600/P-01/003F 

NCEA-I-1200 

March 2002 

www.epa.gov 

Disclaimer 

Mention of trade names or commercial products does not constitute endorsement or 

recommendation for use. 

Cover page credits: Bald eagle, U.S. FWS; mink, Joe McDonald/Corbis.com; child, 

family photo, Jesse Paul Nagaruk; polar bear, U.S. FWS; killer whales, Craig Matkin. 

Contents 

Contributors ................................................................................................. vii 


Executive Summary .......................................................................................ix


Chapter 1. Genesis of the Global Persistent Organic Pollutant Treaty ............ 1-1 


Why Focus on POPs? ................................................................................................. 1-2


The Four POPs Parameters: Persistence, Bioaccumulation, 


Toxicity, Long-Range Environmental Transport ......................................................... 1-5


Persistence ......................................................................................................... 1-5


Bioaccumulation ................................................................................................. 1-6


Toxicity .............................................................................................................. 1-7


Long-Range Environmental Transport .................................................................. 1-7 


POPs History—Cut Short ........................................................................................... 1-8 


UNEP Global POPs Negotiations .............................................................................. 1-10


Science Clarifications—Separating Facts from Assumptions ...................................... 1-12


References ............................................................................................................... 1-15


Chapter 2. Profiles of the POPs .................................................................. 2-1 


1. Intentionally Produced POPs: Pesticides .................................................................2-3 


Cyclodiene Insecticides ..........................................................................................2-3 


Dichlorodiphenyl trichloroethane (DDT)..................................................................2-7 


Toxaphene .........................................................................................................2-11 


Hexachlorobenzene........................................................................................... 2-11


2. Intentionally Produced POPs: Industrial Chemicals ............................................. 2-13


Polychlorinated Biphenyls (PCBs) ....................................................................... 2-13


3. Byproduct POPs ............................................................................................... 2-15


Polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated 


dibenzofurans (PCDF) .......................................................................................2-15 


References ............................................................................................................... 2-18


Appendix. Selected Federal Sites for POPs Toxicity Information .............................. 2-22


Chapter 3. Persistent Organic Pollutant Residues and Their 


Effects on Fish and Wildlife of the Great Lakes ............................................ 3-1 


Introduction ............................................................................................................... 3-1


Fish .......................................................................................................................... 3-3 


Lake Trout ......................................................................................................... 3-4


Birds .......................................................................................................................... 3-6


Bald Eagles ......................................................................................................... 3-7


Colonial Fish-Eating Birds.................................................................................... 3-9


Mammals ................................................................................................................. 3-10


iii 

Contents 

Conclusions .............................................................................................................. 3-12 


References ............................................................................................................... 3-13 


Chapter 4. Persistent Organic Pollutants in the Great Lakes: 


Human Health Considerations ..................................................................... 4-1 


Introduction .................................................................................................................4-1 


Historical Background on POPs Exposure Studies in the Great Lakes ...............................4-2 


Identification of Critical Great Lakes Pollutants ........................................................... 4-2


ATSDR Great Lakes Human Health Effects Research Program ................................... 4-3


Epidemiological Data ................................................................................................. 4-4


Reproductive Effects .................................................................................................. 4-5


Neurodevelopmental Effects ....................................................................................... 4-6


Other Cognitive and Systemic Health Effects ............................................................. 4-8


Fish and Wildlife Advisories ........................................................................................ 4-9


Conclusion ............................................................................................................... 4-12 


References ............................................................................................................... 4-12 


Chapter 5. Alaska—At Risk ........................................................................ 5-1 


Why Alaska Is at Special Risk ........................................................................................5-2 


POPs Transport to Alaska .......................................................................................... 5-4


Atmospheric Transport ....................................................................................... 5-4


Hydrologic Transport........................................................................................... 5-5


Migratory Species ............................................................................................... 5-5


POPs Levels in Alaska................................................................................................ 5-6 


Wildlife Levels ............................................................................................................ 5-7


Bald Eagle .......................................................................................................... 5-7


Peregrine Falcon ................................................................................................. 5-8


Killer Whale ........................................................................................................ 5-9


Sea Otter ......................................................................................................... 5-10 


Species Consumed by Humans ................................................................................ 5-11 


Beluga .............................................................................................................. 5-11 


Bowhead Whale................................................................................................ 5-12 


Seals ................................................................................................................ 5-12 


Steller Sea Lion ................................................................................................ 5-13 


Salmon ............................................................................................................. 5-14 


Polar Bear ........................................................................................................ 5-15 


Native Peoples of Alaska ......................................................................................... 5-15 


POPs Levels in Alaska Natives ................................................................................. 5-17 


Ongoing POPs Research in Alaska ........................................................................... 5-18 


Conclusion ............................................................................................................... 5-19 


References ............................................................................................................... 5-20 


Chapter 6. Accumulation and Effects of Persistent Organic Pollutants in 


Marine Ecosystems and Wildlife ................................................................... 6-1 


Introduction .................................................................................................................6-1 


Transport of POPs and the Role of Oceans as Sinks .......................................................6-1 


Status and Trends of POPs in North American Marine Ecosystems ..................................6-2 


Routes of Exposure of Marine Mammals and Seabirds to POPs ................................... 6-3


iv 

Contents 

Adverse Effects on Wildlife ......................................................................................... 6-4


Inshore Birds ....................................................................................................... 6-5


Offshore Birds .................................................................................................... 6-7


Marine Mammals ................................................................................................ 6-8


Other Marine Mammals: Pinnipeds, Manatees, and Otters ................................ 6-11 


Summary and Conclusions ........................................................................................ 6-12 


References ............................................................................................................... 6-13 


Chapter 7. Long-Range Environmental Transport of Persistent 


Organic Pollutants ...................................................................................... 7-1 


Introduction .................................................................................................................7-1 


Atmospheric Transport of Pollutants to the United States ................................................7-2 


Atmospheric Chemistry of POPs ...................................................................................7-4 


Global Distillation of POPs ............................................................................................7-6 


Calculating and Modeling Atmospheric Transport of POPs .......................................7-8 


POPs Transport in Water............................................................................................7-11 


POPs Transport by Migratory Animals ...................................................................... 7-12 


Monitoring and Modeling POPs Trends ..................................................................... 7-13 


References ............................................................................................................... 7-13 


Chapter 8. Contemplating POPs and the Future........................................... 8-1 


General Worldwide Growth Projections ..........................................................................8-2 


Population Growth ...............................................................................................8-2 


Economic Activity ............................................................................................... 8-3


Agricultural Output ............................................................................................. 8-3


Energy Consumption........................................................................................... 8-4 


Sector-Specific Growth Projections ............................................................................. 8-4


Housing Starts and Termite Control .................................................................... 8-4


Municipal Waste Generation and POPs Byproducts .............................................. 8-5


Industrial Processes and POPs Byproducts ........................................................... 8-6


Summary ................................................................................................................... 8-6


References ................................................................................................................. 8-7


Chapter 9. The Addition of Chemicals—A Living Agreement ......................... 9-1 


The Addition Process ...................................................................................................9-2 


Scientific Foundation for Adding Chemicals ...................................................................9-3 


Screening Criteria ........................................................................................................9-3 


Persistence ...........................................................................................................9-3 


Bioaccumulation ...................................................................................................9-5 


Long-Range Environmental Transport ....................................................................9-7 


Adverse Effects/Toxicity ................................................................................... 9-10 


The Risk Profile ....................................................................................................... 9-11 


Risk Management Options ....................................................................................... 9-11 


The Decision ........................................................................................................... 9-12 


The Future ............................................................................................................... 9-12 


References ............................................................................................................... 9-12 


Appendix A. Transport Pathways ................................................................ A-1 


v 


Contributors 

Editor 

Bruce D. Rodan 

Authors 

Chapter 1. Genesis of the Global Persistent Organic Pollutant Treaty 

Bruce D. Rodan 

Chapter 2. Profiles of the POPs 

Kathleen R. Walker, Susan Y. Euling 

Chapter 3. Persistent Organic Pollutant Residues and Their Effects on Fish and Wildlife 

of the Great Lakes 

John P. Giesy, Paul D. Jones, Kurunthachalam Kannan, Alan L. Blankenship 

Chapter 4. Persistent Organic Pollutants in the Great Lakes: 

Human Health Considerations 

Heraline E. Hicks, Christopher T. De Rosa 

Chapter 5. Alaska—At Risk 

Carl M. Hild, Kimberlee B. Beckmen, James E. Berner, Lin Kaatz Chary, Kari J. 

Hamrick, Philip C. Johnson, Peggy M. Krahn, Suzanne K. M. Marcy, Craig O. Matkin, 

Carol H. Rubin, Marianne G. See, Michael J. Smolen, Lori A. Verbrugge 

Chapter 6. Accumulation and Effects of Persistent Organic Pollutants in Marine 

Ecosystems and Wildlife 

Paul D. Jones, Kurunthachalam Kannan, Alan L. Blankenship, John P. Giesy 

Chapter 7. Long-Range Environmental Transport of Persistent Organic Pollutants 

Joseph P. Pinto 

Chapter 8. Contemplating POPs and the Future 

Hugh M. Pitcher 

Chapter 9. The Addition of Chemicals—A Living Agreement 

Bruce D. Rodan, David W. Pennington, Noelle Eckley, Robert S. Boethling 

Acknowledgment: The authors wish to thank the many internal EPA peer reviewers, the 

external peer review panel (Drs. Peter deFur, Derek Muir, Bernard Weiss), and the members of the public who submitted comments for their valuable insights, suggestions, and 

additions. 

vii 


Executive Summary 

Persistent organic pollutants (POPs) are a small 

group of organic chemicals exhibiting the combined properties of persistence, bioaccumulation, 

toxicity, and long-range environmental transport. 

This small group of pollutants encapsulates the 

genesis and development of pollution awareness 

in the United States. These are the pollutants 

that Rachel Carson described in Silent Spring, 

that contaminated Agent Orange during the 

Vietnam War, and that contributed to Love Canal, Times Beach, and the pollution of the Great 

Lakes. Legislative, regulatory, legal, and voluntary actions in the United States have eliminated 

domestic production of many POPs as pesticides 

and industrial chemicals, and have greatly reduced their emissions as byproducts. Yet, although uses and levels in the lower 48 United 

States have stabilized or declined, elevated levels 

are now being found in what had been thought 

pristine, uncontaminated environments, notably 

in the Arctic and remote oceans. Air and water 

movement are transporting POPs across international borders to these remote locations, where 

they can be elevated to potentially toxic levels 

through biomagnification in the food chain. 

Most poignantly, the first exposure of offspring 

may be through a loading dose of toxicant to the 

fetus or in milk, during the most sensitive period 

of development. 

On May 23, 2001, the United States joined 90 

other nations in signing the Stockholm Convention 

on Persistent Organic Pollutants. Under the Convention, countries commit to reduce and/or eliminate the production, use, and release of the 12 

POPs of greatest concern to the global community and to establish a mechanism by which addiBald eagle, chick, and egg. 

particularly severe on the reproductive success of birds 

of prey. 

Photo: D. Best 

POPs impacts have been 

tional chemicals may be added to the treaty in 

the future. This report is directed toward educating decisionmakers, academia, and the public 

on the science underpinning this global action, 

focusing on the 12 priority substances or substance groups, commonly known as the "dirty 

dozen." 

ix 

Executive Summary 

The 12 Priority POPs of Global Concern 

aldrin 

dieldrin 

endrin 

DDT 

chlordane 

heptachlor 

mirex 

toxaphene 

hexachlorobenzene (HCB) 

polychlorinated biphenyls (PCBs) 

polychlorinated dibenzo-p-dioxins 

polychlorinated dibenzofurans 

The report provides an overview of the human 

and ecological risks posed by POPs to U.S. ecosystems and citizenry. Recognizing the immense 

technical literature on these POPs, the report 

focuses on the most salient topics, while pointing 

to additional literature sources for readers requiring further information. The chapters are based 

on the following general themes: 

❊ Chemical profiles: A narrative introduction is 

provided for each of the 12 

logical evidence of increased preterm human 

births associated with DDT exposure, and its 

demonstrated adverse ecological impacts. 

Notable in this context, the Stockholm Convention provides for continued DDT use for 

disease vector control in countries registering 

such a need, where safe and cost-effective 

alternatives are not available. This use is 

subject to World Health Organization recommendations and guidelines, which allow indoor 

application only. 

❊ Human and ecological effects in the United 

States: Historical and contemporary data are 

summarized demonstrating why POPs gained 

notoriety in the United States and internationally. Two regions are highlighted: the Great 

Lakes and marine ecosystems. In the Great 

Lakes, the contribution of POPs, especially DDT, 

to eggshell thinning and population declines in 

raptors (e.g., bald eagles, osprey, falcons) is well 

known. PCBs and polychlorinated dioxins and 

furans have combined to affect Great Lakes fish 

populations (blue-sac disPOPs. This is accompanied 

Alaska native hunter and boat; a way of life 

for many communities. 

Photo: U.S. Department of the Interior 

ease), fish-eating birds 

by tables summarizing (GLEMED syndrome), and 

important chemical proper- mammalian reproductive 

ties and the regulatory success, especially in mink. 

history covering production For humans, POPs intakes 

and use in the United continue through the conStates. The narrative high- sumption of Great Lakes 

lights selected toxicological sport fish. Epidemiological 

issues not directly discussed evidence in these populaelsewhere in this report. tions has associated PCB 

For instance, the agricul- levels in mothers with adtural problems caused by verse neurodevelopmental 

prolonged, indiscriminate outcomes in their children. 

toxicity from the cyclodiene 

POPs insecticides are noted POPs effects have also been 

(e.g., dieldrin), along with demonstrated in marine ecothe availability over time of system bird and marine mamimproved chemical, physi- mal populations, both in 

cal, and integrated alterna- coastal areas and in remote 

tives for pest management. oceans. In the early 1970s, 

For DDT, particular atten- brown pelican populations on 

tion is drawn to the need U.S. coasts were brought to 

to balance malaria vector the edge of extinction followcontrol in some developing ing DDT-induced eggshell 

countries with epidemio­ thinning, principally mediated 

x 

Executive Summary 

through its long-lived 

Birds on remote Midway atoll in the north Pacific are 

exposed to POPs. 

Photo: NASA 

with passing weather 

metabolite DDE. systems. This cold 

Contemporary el- condensation results in 

evated levels of PCBs a net transport of POPs 

and dioxins accumu- from lower latitudes to 

lated in albatross on high latitudes (polar 

Midway Atoll in the regions) in a series of 

remote North Pacific jumps. The different 

Ocean may be inter- affinities of POPs for 

fering with their re- soil particles, water, 

productive success. and/or lipid molecules, 

and their rate of volatilThese findings from ization, determine the the Great Lakes and pathway and time marine ecosystems course each chemical is 

demonstrate that it is likely to take in its possible to sufficiently journey through the contaminate environments with POPs residues to cause adverse 

effects on a regional and global scale, along 

with the prolonged and continuing nature of 

these impacts. The experience is also one of 

hope, in that controls on the production, use, 

and release of POPs can, and have, resulted in 

reduced environmental concentrations and 

wildlife recovery. The bald eagle saga offers 

an inspiring metaphor. Once nearly extinct in 

the lower 48 United States, bald eagle populations have recovered dramatically with the 

cessation of DDT use in the United States, yet 

the reproductive impacts linger. 

❊ Long-range transport of POPs: POPs move 

to regions such as the Great Lakes, marine 

ecosystems, and the Arctic through long-range 

environmental transport in air, water, and 

migratory species. This transboundary movement occurs principally through the atmospheric pathway, either on suspended particles 

or through a process of global distillation and 

cold condensation. Global distillation results 

from the semivolatile nature of some POPs, 

where they can be present in more than one 

phase in the atmosphere, either as gases or 

attached to airborne particles. Because of the 

normal decrease of temperature with increasing latitude, compounds in the vapor phase 

will tend to condense on surfaces as they are 

transported northward by winds associated 

environment. 

❊ POPs in Alaska: Risks to Arctic environments 

and indigenous human populations were central to negotiating the Stockholm Convention 

on POPs. For the United States, many of the 

physical, climatic, and social aspects that make 

Alaska unique — particularly for the indigenous population — also make this region 

peculiarly prone to risks from global POPs. 

Alaska is downwind and geographically close 

to continuing sources of POPs production and 

use in Asia, where populations and economic 

growth are expanding rapidly. The Alaskan 

climate facilitates the deposition of POPs, 

delays their degradation through environmental 

processes, and places unusual stresses on 

ecosystems. Fat becomes the currency of life 

in the harsh Arctic environment for both wildlife and humans, serving as the ideal medium 

for transferring and magnifying the concentrations of lipophilic POPs between species and 

up the food chain. 

Previously pristine in remote areas, all of 

Alaska's environmental media and species now 

contain measurable levels of POPs. However, 

POPs levels in Alaska are generally low compared with the lower 48 United States. Accompanying these comparatively low levels are isolated examples of elevations that serve as a 

cautionary warning in the absence of internaxi 

Executive Summary 

tional action. DDT and PCB levels in transient 

Alaskan killer whales are as high as those 

found in highly contaminated east coast dolphins. On Kiska Island in the Aleutians, DDT 

levels in bald eagle eggs approach effect levels 

seen in the Great Lakes. And, serum concentrations of DDT and chlordane in a limited 

sample of Alaska Natives underscore their 

proximity to areas of continuing production 

and use internationally. It is important to 

emphasize, however, that there are no known 

POPs levels at this time in Alaska that should 

cause anyone to stop consuming locally obtained, traditional foods or to stop breastfeeding their children. Current information 

indicates that the risks associated with a subsistence diet in Alaska are low, whereas the 

benefits of this diet and breastfeeding children 

are well documented. Further investigation 

and assessment are needed for specific species and foods in traditional diets, and to 

broaden the database across Alaskan 

communities. 

❊ What might the future hold in the absence of 

POPs controls? The passage of time is central 

to evaluating the merits of the Stockholm Convention. Emission scenario models forecast 

large increases in the scale of worldwide economic activity over the next half-century, with 

overall economic activity predicted to increase 

about fourfold in the "business as usual" scenario. The human population is predicted to 

increase to around 9 billion persons. The large 

majority of increases will occur in developing 

countries. Although different model inputs lead 

to different results, all projections share a common future of much higher total economic activity, and hence of potential uses and emissions 

of POPs in the absence of active control policies and alternatives. 

The United States is not alone in having experienced POPs problems, with many countries suffering local and transboundary pollution effects. 

In response, the United States has signed international agreements on persistent toxic substances under the Great Lakes Binational Toxics 

Strategy (US, Canada); the North American 

Agreement on Environmental Cooperation (US, 

Canada, Mexico); and the UNECE Long-Range 

Transboundary Air Pollution POPs Protocol (US, 

Canada, Western and Eastern Europe, Newly 

Independent States, Russia). The consensus for 

global action on POPs under the Stockholm Convention is commensurate with the extent of the 

pollution and the need to include all countries in 

the solution. To this end, the Convention contains the following central elements: 

❊ Measures to eliminate or restrict the production, use, and trade of intentionally produced 

POPs 

❊ Development of action plans to address the 

release of byproduct POPs, along with the obligation to use best available techniques to reduce 

byproduct emissions from newly constructed 

facilities in specified major industrial source 

categories 

❊ Measures to reduce or eliminate POPs releases 

from stockpiles and wastes 

❊ Technical and financial assistance to developing countries, and countries with economies in 

transition, to implement their obligations under 

the Convention 

❊ Science-based criteria and procedures for the 

addition of new POPs chemicals 

The Stockholm Convention will enter into force 

following ratification by 50 nations. The Convention is aimed at protecting human health and 

the environment from POPs chemicals on a global scale. Through implementation of the Convention, nations have the opportunity to make 

POPs a relic of the 20th century, and a warning 

from history for the 21st century. 

xii 

Chapter 1 Genesis of the Global Persistent 

Organic Pollutant Treaty 

Each day the resilience of the Earth offers humanity a new beginning by mitigating the pollution and wastes of yesterday. Through wind and 

water, pollutants are dispersed and diluted; 

through chemical and biological degradation, 

toxic substances are eliminated; and through the 

fidelity of DNA replication, life begins anew. 

But for a small group of persistent organic pollutants (POPs), natural processes and ecosystem 

services have proven inadequate to rectify, and 

in some cases have contributed to, environmental 

contamination. The resistance of POPs to degradation and their environmental persistence 

serve as a foundation for prolonged and disseminated adverse effects. Air and water move 

POPs far from their sites of release to the environment, including to previously pristine locations 

such as the Arctic. The low levels of POPs 

reaching remote locations can then be elevated 

to potentially toxic levels through biomagnification in the food chain. And, most poignantly, 

the first exposure of offspring may be through a 

loading dose of toxicant to the fetus or in milk, 

during the most sensitive period of development. 

PCB concentrations are elevated in Aleutian Island sea 

otter populations. 

Photo: U.S. Fish and Wildlife Service 

It is to this group of substances—the persistent 

organic pollutants—that this technical report is 

addressed. 

The report summarizes the science underpinning 

contemporary action on POPs, focusing on the 

12 substances or substance groups prioritized for 

global action in the recently signed Stockholm 

Convention on Persistent Organic Pollutants, 

developed under the auspices of the United 

Nations Environment Programme (UNEP). These 

12 substances, the "dirty dozen," are: 

❊ Pesticides: dieldrin, aldrin, endrin, chlordane, 

heptachlor, DDT, toxaphene, mirex 

❊ Industrial chemicals: polychlorinated biphenyls 

(PCBs; also a byproduct), hexachlorobenzene 

(HCB; also a pesticide and byproduct) 

❊ Byproducts: polychlorinated dibenzofurans, 

polychlorinated dibenzo-p-dioxins (dioxin) 

The report is directed toward educating decisionmakers, academia, and the public on the foundation and relevance to the United States of the 

Stockholm Convention on POPs. The report 

consolidates and summarizes the large volumes 

of data developed on these substances over decades of scientific concern and regulatory experience, as published in multiple source documents 

from individual peer-reviewed literature, through 

single-chemical profiles, to multivolume risk 

assessments. Its objective is to provide an overview of the human and ecological risks posed by 

POPs to U.S. ecosystems and citizenry. Emphasis is placed on making the document easily 

readable, while maintaining its technical accuracy 

and balance. To this end, citations are provided 

to more comprehensive and detailed literature 

for those seeking a more complete elaboration of 

technical issues. 

1-1 

Genesis of the Global POPs Treaty 


Why Focus on POPs? 

Public concern and scientific and regulatory efforts regarding this small group of pollutants 

encapsulate the genesis and development of 

environmental pollution awareness in the United 

States. These are the pollutants that Rachel 

Carson wrote about in Silent Spring (Carson, 

1962), that contaminated Agent Orange during 

the Vietnam War, and that contributed to Love 

Canal, NY, Times Beach, MO, and numerous 

other pollution episodes. All 12 substances prioritized under the Stockholm Convention are now 

deregistered, banned, or out of production in the 

United States, or their emissions have undergone 

major reductions. Yet their effects are still felt 

through a legacy of past pollution, continuing 

emissions, and movement across international 

borders. 

For the nine organochlorine pesticides (including 

hexachlorobenzene as a fungicide), the extent of 

adverse human health and/or ecological effects 

Poor storage of donated DDT in Zanzibar. 

Photo: R. Hedlund, USAID 

Dieldrin-containing drums in Niger. 

Photo: Janice Jensen 

led to the withdrawal of all registered uses in the 

United States during the 1970s–1990s, either by 

the U.S. Environmental Protection Agency (EPA) 

or voluntarily by the registrant. Production of the 

last of these, heptachlor, has ceased and its 

registration was voluntarily cancelled in 2000. 

Because U.S. pesticide laws are based on registrations for specific uses, problem chemicals are 

dealt with through withdrawal of these registrations, rather than bans on production. The net 

effect of these actions is that there is currently 

no production of any of the POPs in the United 

States for sale domestically or internationally, 

except for laboratory-scale research consistent 

with the requirements of the Stockholm Convention. 

For polychlorinated biphenyls (PCBs), the magnitude of environmental problems was central to 

the passage of the Toxic Substances Control Act 

(TSCA). PCB production was banned under this 

legislation in 1979, although production ceased 

prior to this date. Existing PCBs in electrical 

equipment must be prevented from entering the 

environment and destroyed at the end of the 

equipment's service life. Polychlorinated 

dibenzo-p-dioxins and polychlorinated 

dibenzofurans, better known as "dioxins," have 

been controlled through a variety of means, principally emission controls on incinerator sources, 

process changes to remove elemental chlorine 

from pulp and paper production, and the 

1-2 

Genesis of the Global POPs Treaty 

deregistration of contaminated herbicides such as 

2,4,5-trichlorophenoxyacetic acid (2,4,5-T; a 

constituent of Agent Orange). 

The breadth of POPs pollution that led to these 

U.S. regulatory actions is still evident in contemporary environmental concentrations. POPs 

pollution has touched every region of the United 

States, as illustrated by the geographic distribution of DDE (a long-lived toxic metabolite of 

Figure 1-2. 

for polychlorinated biphenyls (PCBs) to the U.S. EPA by 

states, territories, and Native American tribes. 

ter 4 for further details on fish advisories. A 1999. 

1998 fish consumption advisories reported 

See ChapU.S. EP

Figure 1-1. 1986–1998 mean sum-DDT and sum-PCB 

concentrations in coastal mussels (dry weight) collected 

by the National Oceanic and Atmospheric Administration 

(NOAA) through its ongoing Status and Trends Mussel 

Watch Program. 

of Tom O’Connor, NOAA. See also trends discussion in 

Chapter 6. 

http://ccma.nos.noaa.gov. Data courtesy 

DDT) and PCB concentration elevations in 

coastal mussels (Figure 1-1), PCB fish advisories 

(Figure 1-2), and contemporary measurements of 

atmospheric dioxin levels in nonurban locations 

across the United States (Figure 1-3). Impacts 

on the Great Lakes (Chapters 3, 4) and marine 

ecosystems (Chapter 6) are highlighted in this 

report as examples of POPs pollution exposures 

and effects, along with a summary of the 

existing science on POPs concentrations and 

risks in Alaska (Chapter 5). Many more sites of 

POPs contamination are scattered across the 

United States, but these cannot be detailed here 

because of space constraints. One such example 

is Lake Apopka in Florida, where high levels of 

several POPs (principally DDE) and other 

pollutants (Figure 1-4) have been postulated as 

causing reproductive impairment and male 

genital abnormalities in alligators following 

embryonic exposure, although the specific causal 

agent(s) remains uncertain (Guillette et al., 

1999). 

The extent to which POPs remain problematic is 

also manifest through continuing regulatory and 

policy initiatives, both domestically and in international fora in North America. Domestically, 

the EPA is engaged in a variety of initiatives on 

persistent, bioaccumulative, toxic (PBT) chemi1-3 
1-4

Genesis of the Global POPs Treaty

cals. s encompass a somewhat broader domain than POPs, including metals, whereas

POPs are limited to organic substances (i.e., containing carbon). 

EPA's PBT program to coordinate action regarding these pollutants (www.epa.gov/pbt), the

Toxics Release Inventory (TRI) PBT reporting requirements under the Emergency Planning and

Community Right-To-Know Act (EPCRA)

(www.epa.gov/tri/pbtrule.htm), and the

prioritization accorded PBT parameters when

evaluating new chemical notifications under the

Toxic Substances Control Act (TSCA) and when

registering pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).

Internationally, the Great Lakes Binational Strategy with Canada prioritizes primary and secondary lists of substances slated for "virtual elimination" (www.epa.gov/glnpo/p2/bns.html). 

to these lists are the 12 priority POPs listed in

the Stockholm Convention. 

the environmental side agreement of the North

American Free Trade Agreement (NAFTA), the

United States and Canada have focused their

Safe Management of Chemicals (SMOC) efforts

on PBTs (www.cec.org). 

developed for DDT, PCBs, and chlordane, as well

as mercury, and are under development for dioxins, furans, and hexachlorobenzene.

Figure 1-3. 

dioxin TEQ (from PCDDs, PCDFs, coplanar PCBs) in

femtograms (10-15 grams) per cubic meter for the year

2000, collected by the National Dioxin Air Monitoring

Network (NDAMN). 

ences. ce: David Cleverly, U.S. EPA

Sites: 1 - Penn Nursery, PA; 2 - Penn Nursery, PA, QA duplicate;

3 - Clinton Crops, NC; 4 - Everglades National Park, FL; 5 - Lake

Dubay, WI; 6 - Monmouth, IL; 7 - McNay, IA; 8 - Lake Scott, KS;

9 - State Park West of Tulsa, OK; 10 - Arkadelphia, AR;

11 - Bennington, VT; 12 - Jasper, NY; 13 - Beltsville, MD;

14 - Caldwell, OH; 15 - Oxford, OH; 16 - Dixon Springs, IL;

17 - Quincy, FL; 18 - Stennis Space Center, MS - insufficient data

in Yr. 2000; 19 - Padre Island, TX; 20 - Fond du Lac Indian

Reservation, MN; 21 - North Platt Agricultural Experiment

Station, NE; 22 - Goodwell Research Station, OK; 23 - Big Bend

National Park, TX; 24 - Grand Canyon National Park, AZ;

25 - Theodore Roosevelt National Monument, ND; 26 - Craters of

the Moon National Park, ID; 27 - Chiricahua National Park, AZ;

28 - Proposed Dairy Reseach Facility, CA; 29 - Hyslop Farm, OR;

30 - Lake Ozette, WA; 31 - Fort Cronkite, San Francisco, CA;

32 - Craig, AK, recently operational; 33 - Trapper Creek, AK,

recently operational.

Figure 1-4. A. Mean serum levels of POPs in juvenile

male and female alligators from three different lakes in

the same drainage in Florida (Guillette et al., 1999).

B. A yearling alligator swimming in the eutrophic water

of Lake Apopka.

Photo: Howard K. Suzuki Serum Contaminants (ng/ml)

PBT

Domestic activities include the

Central

With Mexico, under

Action plans have been

Average atmospheric concentrations of

Site locations listed after referSour
Genesis of the Global POPs Treaty 

Contributing to the difficulties in eliminating 

some POPs are their advantages in the industrial 

and building sectors. PCBs made excellent dielectric fluids in electrical capacitors and transformers because they are highly resistant to degradation and fire. These same properties 

contribute to their persistence in the environment 

and biological organisms. A single application of 

chlordane, an organochlorine termiticide, provides household termite protection for years. 

Unfortunately, not all the chlordane stays where 

it is applied, and it may continue to 

bioaccumulate far from basement soil and injure 

or kill creatures for which it was not intended. 

DDT’s ability to repel and injure or kill malariacarrying mosquitoes can provide several months 

of household protection, yet ultimately DDT is 

mobilized and spread outside of the immediate 

area of application. The benefits of DDT for 

malaria control, principally due to its persistence, 

low cost, and past success, remain a major consideration when balancing public health needs 

with environmental concerns. 

The Four POPs Parameters: Persistence, 

Bioaccumulation, Toxicity, Long-Range 

Environmental Transport 

A suite of four characteristic parameters distinguish POPs from the multitude of other organic 

chemicals: 

Persistence 

Persistence is the propensity of a substance to 

remain in the environment by resisting chemical 

and biological degradation, particularly the effects of microbial processes. Persistence is best 

represented as the degradation of a POP to a 

non-POP chemical, rather than as declining environmental concentrations that combine degradation with loss due to dispersion. Persistence is 

often measured as a half-life, the time (hours, 

days, months, or even years) necessary for half 

the chemical to be degraded. Reliance on halflife measures assumes first-order kinetics, where 

the amount degraded in a fixed period of time is 

a constant proportion of the amount present 

initially, i.e., Ct

 = C0 e–rt, where C0 and Ct are 

concentrations at times zero and t, and r is the 

rate constant for degradation (Figure 1-5). The 

first-order kinetics assumption may not always 

apply where early degradation is more rapid, 

delayed degradation is enhanced through bacterial acclimation and selection, or chiral (mirror 

image) molecules may be preferentially degraded. The degradation product may also exhibit POPs characteristics. Half-life values in the 

different air, soil, water, and sediment media 

have been included in most POPs screening 

criteria (see Chapter 9, Table 9-1). These halflife values are considered pragmatically useful for 

screening chemicals, but are recognized as oversimplifying the persistence of chemicals in the 

environment (Klecka et al., 2000). Persistence 

screening values for the Stockholm Convention 

are based on 2 months in water or 6 months in 

soil or sediment, with a 2-days screening criterion for air transport. 

Environmental degradation in the atmosphere 

occurs principally from reaction of the POP with 

hydroxyl radicals (OH). The levels of hydroxyl 

radicals in the air vary considerably with geographic location and time of day and year. For 

instance, hydroxyl levels are essentially zero in 

the Arctic atmosphere during winter and generally decline with increasing latitude. Other atmospheric POPs degradation processes include photolysis (light-induced degradation) and reaction 

First-Order Kinetics 

Half-life 6 months 

Figure 1-5. First-order decay kinetics diagram. 

1-5 

Genesis of the Global POPs Treaty 


with ozone and nitrogen oxides. In soil, water, 

and sediment, microbial degradation is the predominant mechanism. The rate of degradation 

depends on the types of bacteria present, their 

concentration, induction relevant to the chemical 

undergoing degradation, and ambient environmental conditions such as temperature, moisture, 

and substrate availability. Other processes include photolysis, hydrolysis, and chemical reaction. Details of technical considerations in deriving and using persistence data are contained in 

the report of a Society of Environmental Toxicology and Chemistry (SETAC) Pellston workshop, 

focusing on POPs persistence and long-range 

transport issues (Klecka et al., 2000). 

Bioaccumulation 

Bioaccumulation is the phenomenon whereby a 

chemical reaches a greater concentration in the 

tissues of an organism than in the surrounding 

environment (water, sediment, soil, air), principally through respiratory and dietary uptake 

routes. For example, if the environment in 

which a fish lives contains 1 μg free chemical/kg 

of water, and the fish’s body contains 5,000 μg 

chemical/kg body weight, this would equate to a 

whole-body bioaccumulation factor (BAF) of 

5,000 (i.e., the Stockholm Convention screening 

criterion value). The magnitude of 

bioaccumulation is driven by the hydrophobicity, 

or water insolubility, of the chemical, principally 

operating through the ability of a species to 

eliminate the chemical from its body by excretion 

and/or metabolism. The terms bioaccumulation, 

bioconcentration, and biomagnification are variants of this same concept. Bioaccumulation 

factors measure the preferential accumulation of 

a chemical in a living organism through all routes 

of uptake with respect to concentrations in the 

organism’s exposure environment (water, sediment, soil). The term “bioconcentration factor” 

(BCF) is used when the bioaccumulation factor is 

based exclusively on uptake from water in laboratory studies, using species (most commonly 

fish) maintained in a known concentration of 

pollutant but fed an uncontaminated diet. 

Biomagnification relates to the most highly accumulative substances (many of the POPs), where 

the concentration of the chemical in an organism 

exceeds that predicted for equilibrium of the 

organism with its diet, the concentration having 

been “magnified” in species higher up the food 

chain (Figure 1-6). 

BCF/BAF values can be reported either in relation to the whole-body weight of the test species 

or in a more standardized manner related to the 

lipid (or fat) content of the animal, usually a fish. 

These two measures can be quantitatively linked 

through the fat content of the animal because 

the POPs are concentrated in the fatty portions 

of tissues. This relationship is often simplified by 

assuming a standard fish fat content to facilitate 

comparison between chemicals in different study 

protocols and species, known as lipid normalization (e.g., 3.1% lipid in the case of the Great 

Lakes Water Quality Assessment for trophic level 

3 fish). 

A common surrogate for calculating BCF/BAF 

values is the octanol-water partition coefficient 

(Kow). This ratio reflects the preferential accumulation of a substance in an organic medium 

(n-octanol) compared with water. To illustrate, in 

a cup containing half n-octanol and half water, 

this is the amount of a chemical placed in the 

cup that would dissolve in the n-octanol divided 

by the amount dissolving in the water. The Kow 

is now most often calculated using chemical 

models. It should be noted that mathematical 

Figure 1-6. Simple biomagnification diagram. 

1-6 

Genesis of the Global POPs Treaty 

formulae linking the Kow with BCF/BAF values 

do not apply where there is active metabolism of 

the substance, or for large molecules, and are 

generally not applicable to organometals. Additional detail on bioaccumulation in aquatic environments is available in the U.S. EPA Great 

Lakes Water Quality Criteria documents (U.S. 

EPA, 1995). 

Toxicity 

A principal tenet of toxicology is that the dose 

makes the poison (Paracelsus, 1493–1541), a 

concept elaborated upon more recently as knowledge has increased on the complexity and timing 

of dose-response relationships. The toxicity of a 

substance can be reported in a variety of ways, 

such as acute (short-term) or chronic (long-term) 

effects, lethal or effective dose levels (LD50 or 

ED50, the dose that will kill or affect 50% of test 

animals), or tissue levels associated with an adverse effect. Whereas certain toxic effects and 

levels may be easily detected and quantified in 

laboratory settings, their measurement in the 

natural environment is considerably more difficult. In field situations, the animal's environment is impossible to control. 

This situation is similar to the difficulties 

experienced with human epidemiological studies. 

Multiple substances may combine to form a 

“toxic soup” from which individual chemical 

contributions can be difficult to disentangle. A 

corollary of multiple simultaneous exposures is 

that the cumulative toxicity risk is likely to be 

greater than when individual chemicals are 

evaluated in isolation. Furthermore, the low-level 

effects of interest in field situations may be 

subtle and difficult to measure, yet vital to 

species survival. For example, subtle POPsinduced neurological impairment may not cause 

overt effects in a caged, fed, and protected 

animal, but may be of dire consequence in the 

complex and dangerous natural environment. 

Difficulties also occur when attempting to 

transpose laboratory toxicity data, generally 

measured as daily dose, to field situations where 

the metric is tissue concentration of a toxic 

substance and daily doses cannot be measured. 

For a further detailed discussion of wildlife toxicology and the effect levels pertinent to POPs 

impacts on wildlife, see Beyer et al. (1996). 

Toxicity data on POPs pertinent to humans can 

be obtained from online databases maintained by 

the National Library of Medicine 

(www.nlm.dhhs.gov; Hazardous Substances 

Data Bank), the EPA's Integrated Risk Information System (IRIS) database (www.epa.gov/iris), 

and the Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological Profiles 

(www.atsdr.cdc.gov). 

Long-Range Environmental Transport 

There would be little need for a global treaty if 

POPs remained close to their sites of release. 

However, on a dynamic planet the forces of air 

and water, along with the migratory behavior of 

certain species, move these pollutants to remote 

locations (see Chapter 7 for details). A major 

impetus for the global POPs negotiation was the 

finding of POPs contamination in the Arctic, 

thousands of miles from their presumed sites of 

release to the environment. Figure 1-7 shows 

the intermittent transport of massive dust clouds 

from Asia and North Africa toward North 

America. Within a few days these clouds can 

cross the Atlantic and Pacific Oceans, transporting pollutants and microorganisms along with the 

dust. Images such as this provide visual confirmation of atmospheric pathways between continents. 

Figure 1-7. False color image of the aerosol abundance in 

the atmosphere obtained by NASA’s Earth Probe TOMS 

satellite. 

tion of solar ultraviolet radiation by airborne particles. 

Source: National Aeronautics and Space Administration 

The aerosol index is a measure of the absorp1-7 

Genesis of the Global POPs Treaty 


Beyond physical transport on dust and sediment 

particles, empirical data and the physical properties of a number of POPs indicate that these 

substances may be preferentially accumulating in 

cold polar climates through global distillation. 

Certain POPs that exhibit a particular range of 

physical properties—often characterized as 

semivolatile—may evaporate in tropical and 

temperate climates and condense in cold regions. 

In a more absolute sense, and independent of 

whether transport occurs via volatilization or 

physical transport on particles or in water, once a 

substance reaches the frozen polar regions, normal physical degradation time scales and halflives lose their relevance. 

It is the combination of persistence, bioaccumulation, toxicity, and long-range environmental 

transport that makes POPs problematic. All 12 

prioritized POPs or their breakdown products 

rank high to extreme on measurements of these 

parameters. Low values on any of the parameters will substantially reduce transboundary concern, although local problems may remain. The 

parameters also serve as the basis for screening 

levels in virtually all international POPs agreements, including the Stockholm Convention. In 

screening for potential POPs using these parameters, the limitations of such an approach are 

recognized through an emphasis on flexibility and 

expert judgment in determining the level of risk 

produced by a substance and what action is 

warranted. 

POPs History—Cut Short 

The story of POPs begins with the growth of the 

organic chemical industry in the early 20th century, and with foresight will end as we enter the 

21st century. DDT was first synthesized in 

1874, but its insecticidal properties remained 

unknown until reported in 1939 by the Swiss 

chemist Paul Hermann Müller. A skin rash called 

chloracne was reported by Karl Herxheimer 

(Herxheimer, 1899) to be afflicting German 

workers in the chlorinated organic chemical industry in 1899, although the causal agent, dioxin, remained elusive for many decades (Figures 

1-8, 1-9). PCBs were first produced commercially in 1929, peaked in 1970, and were 

banned from production in the United States by 

1979. Dieldrin and aldrin were first synthesized 

as pesticides in the United States in the late 

1940s. They were named for Drs. Otto Diels 

and Kurt Alder, who developed the Diels-Alder 

process for diene (2 double bonds between carbon atoms) synthesis in 1928. With World War II 

and reconstruction came a broad public awareness of the potential marvels of chemicals such 

as DDT for disease vector control, exemplified 

by international efforts seeking to eradicate diseases such as malaria. At the same time, newly 

developed organochlorine pesticides and herbicides were rapidly filling the needs of the growing agrochemical industry. 

But as the use of halogenated, particularly chlorinated, organic chemicals rose in agricultural and 

industrial sectors, so did warnings about potential 

adverse consequences to human health and the 

environment. In 1962, a sentinel event occurred 

with the publication of Rachel Carson's Silent 

Spring. Through this book and the surrounding 

media attention, the public first became aware 

of a downside to the proliferation of chemicals, 

with warnings of spring devoid of songbirds. 

Chemicals intended for insect control were being 

found to accumulate in the food chain, causing 

eggshell thinning, chick mortality, and other 

Figure 1-8. Agent Orange barrels during the Vietnam 

War, contaminated with dioxin. 

Source: USAF 

1-8 

Genesis of the Global POPs Treaty 

Figure 1-9. Aerial spraying Agent Orange defoliant, 

Vietnam. 

Source: USAF 

unforeseen damage. Adding halogen atoms 

(fluorine, chlorine, bromine, iodine) had been 

used to make organic molecules more resistant 

to degradation. The persistence of these organochlorine structures, and the propensity of some 

to bioaccumulate, were central to the problems 

being experienced. Increased persistence meant 

that mistakes made with POPs lingered, such as 

the prolonged ecological damage caused by 

chemical spills. Because persistent organochlorine pesticides were nonselective in their toxicity 

to insects, they caused prolonged killing of both 

pest insects and beneficial creatures that preyed 

on these pests. Prolonged, indiscriminate lethality also precipitated secondary pest outbreaks, 

where insect species not generally considered a 

problem rose in prominence through disruption 

of ecological processes. 

Beyond these agricultural and ecological concerns 

lay the human dimension of pesticide and PCB 

residues in the food supply. Data from tests in 

rodent species showed that many of these substances were possible or probable human carcinogens. Passage of the Delaney Clause in the 

1958 Food Additives Amendment to the Food, 

Drug, and Cosmetic Act (FDCA) mandated that 

no carcinogens be added to the food supply—a 

zero-risk policy. Legal and regulatory decisions 

to operationalize this requirement stimulated 

efforts to quantify cancer risk estimates and led 

to the concept of a de minimus concentration, a 

level below which risks were considered too small 

to warrant legal attention. The organochlorine 

POPs, both industrial and chemical, were central 

to many of these debates. Compounding this 

pressure for risk quantification was increasing 

public concern about contaminated industrial 

sites and toxic chemical pollution. In response, a 

combination of legislative, regulatory, legal, and 

voluntary actions ultimately facilitated the development and use of newer pesticides and industrial alternatives in the United States, replacing 

the problematic organochlorines. 

But while uses and levels in the environment, 

food, and tissue were stabilizing or declining in 

the lower 48 United States, reports began appearing in the scientific literature of increasing 

levels in what had been thought pristine, uncontaminated environments. In particular, increasing haze and contamination in the Arctic became 

a priority concern of northern countries. In 

1991, Environment Ministers from the Arctic rim 

countries (Canada, Denmark/Greenland, Finland, 

Iceland, Norway, Sweden, Russia, United States; 

Figure 1-10) established the Arctic Monitoring 

and Assessment Programme (AMAP; 

www.amap.no) to measure the levels and assess 

the effects of man-made pollutants in the Arctic 

environment. Priority attention was directed 

toward POPs, together with heavy metals and 

radioactivity. The AMAP efforts, consolidating 

and supported by domestic programs in Arctic 

countries (e.g., Canadian Northern Contaminants 

Program, Jensen et al., 1997), helped focus 

attention on the long-range transboundary movement of POPs. Long-range environmental transport concerns were reinforced with the finding of 

elevated POPs levels in wildlife on remote midPacific islands (Jones et al., 1996). 

Transboundary pollution issues, and the opportunity to address them, also gained greater prominence with the easing of Cold War tensions. In 

1979, member countries of the United Nations 

Economic Commission for Europe (UNECE) had 

signed the Convention on Long-Range 

Transboundary Air Pollution (LRTAP), initially 

directed at controlling transboundary sulfur and 

acid rain pollution. Beyond its name, the 

1-9 

Genesis of the Global POPs Treaty 


Figure 1-10. Arctic topography and bathymetry. 

Source: AMAP. 

UNECE region includes Canada, the United 

States, Western Europe, Eastern Europe and 

Newly Independent States, and Russia, circling 

the upper Northern Hemisphere. With a growing understanding of the transboundary nature of 

POPs pollution, the UNECE-LRTAP agreement 

offered an ideal vehicle to advance POPs control 

efforts. In 1992, background work commenced 

on parallel UNECE-LRTAP protocols to address 

POPs and heavy metals. Criteria for the priority 

scoring and selection of POPs were developed, 

along with a process for reviewing individual 

chemicals for potential action by the LRTAP 

parties (AEA, 1995, 1996). Negotiations on a 

formal POPs protocol began in 1994 and were 

completed in 1998 (www.unece.org/enc/lrtap), 

following which the protocol was signed by the 

United States. 

UNEP Global POPs Negotiations 

The written record of the global POPs negotiation traces to Agenda 21 of the Rio Declaration 

on Environment and Development in June 1992 

(United Nations, 1993). The foundation and 

priority for POPs action were enunciated in Objective 17, Protection of the Oceans, and Objective 19, Environmentally Sound Management of 

Toxic Chemicals. Under Protection of the Marine Environment, section 17:18 stated: 

Many of the polluting substances originating 

from land-based sources are of particular 

concern to the marine environment since 

they exhibit at the same time toxicity, persistence and bioaccumulation in the food 

chain. There is currently no global scheme 

to address marine pollution from land-based 

sources. 

Similar concerns were echoed in section 19:44, 

Establishment of Risk Reduction Programmes, 

where Agenda 21 called for 

the phasing out or banning of chemicals that 

pose unreasonable or otherwise unmanageable risks to human health and the environment and of those that are toxic, persistent 

and bioaccumulative and whose use cannot 

be adequately controlled. 

In May 1995, these concerns about POPs served 

as the basis for Decision 18/32 of the United 

Nations Environment Programme Governing 

Council (UNEP-GC), which commenced a technical review process to document POPs risks and 

response strategies. The initial list of POPs 

consisted of the 12 under discussion at that time 

by the UNECE-LRTAP Parties. The following 

principal events trace the chronology and developing consensus for international action on 

POPs: 

November 1995: Washington Declaration 

on Protection of the Marine Environment 

from Land-Based Activities (http:// 

www.unep.org/unep/gpa/pol2b12.htm). 

December 1995: Inter-Organization 

Programme for the Sound Management of 

Chemicals (IOMC) Persistent Organic Pollutants Assessment Report (Ritter et al., 1995). 

1-10 

Genesis of the Global POPs Treaty 

March 1996: Intergovernmental Forum on 

Chemical Safety (IFCS), second meeting of 

the Inter-Sessional Group (ISG-2), Canberra, 

Australia (ISG/96.5a). 

June 1996: Intergovernmental Forum on 

Chemical Safety (IFCS) Experts Meeting on 

POPs: Persistent Organic Pollutants: Considerations for Global Action. Manila, Philippines (IFCS/EXP.POPs./Report.1, 20 June 

1996). 

February 1997: UNEP Governing Council, 

Decision 19/13C. International action to 

protect human health and the environment 

through measures that will reduce and/or 

eliminate emissions and discharges of persistent organic pollutants, including the 

development of an international legally binding instrument (http://irptc.unep.ch/pops/). 

Decision 19/13C of the UNEP Governing Council in February 1997 constituted the formal 

agreement to create an intergovernmental negotiating committee (INC) to develop the text for a 

binding global POPs convention. Negotiations 

were to commence in 1998 and conclude by 

2000. Decision 19/13C provided a detailed 

mandate to guide the negotiations, centered 

around the UNEP-GC decision that 

immediate international action should be 

initiated to protect human health and the 

environment through measures which will 

reduce and/or eliminate ... the emissions 

and discharges of the twelve persistent 

organic pollutants specified in Governing 

Council decision 18/32 and, where appropriate, eliminate production and subsequently the remaining use of those persistent organic pollutants that are intentionally 

produced. 

Negotiations began in Montreal, Canada, in June 

1998, following a series of awareness-building 

workshops in developing countries to inform 

governments on scientific issues concerning 

POPs. Subsequent negotiating sessions were 

held in Nairobi (January 1999), Geneva (September 1999), and Bonn (March 2000), culminating 

in the agreement reached in Johannesburg (December 2000) (Figure 1-11). Technical considerations on criteria for the addition of substances 

were covered during two criteria expert group 

(CEG) meetings in Bangkok (October 1998) and 

Vienna (June 1999). Signing of the treaty by the 

United States and 90 other nations was held in 

Stockholm, Sweden, in May 2001, hence the 

designation Stockholm Convention (Table 1-1). 

The treaty is currently open for signature and 

ratification by countries. Ratification by individual countries confirms their signature and 

makes them a party to the treaty, following 

review and consent through the domestic political, legal, and legislative process. The Convention will enter into force after it has been ratified 

by 50 nations. Entry into force applies only to 

parties that have ratified the Convention. 

Science Clarifications—Separating 

Facts from Assumptions 

Before detailing POPs case studies in the United 

States and links to long-range environmental 

transport, it is worthwhile clarifying some assumptions and misconceptions that often occur 

when evaluating POPs. In particular, an underFigure 1-11. Concluding the POPs negotiations, 

Johannesburg, South Africa, December 2000. 

Source: International Institute for Sustainable Development. 

1-11 

Genesis of the Global POPs Treaty 


Table 1-1. Elements of the Stockholm Convention 

Objective: "... to protect human health and the environment from persistent organic 

(Article 1) pollutants." 

Article 2 Definitions 

Article 3 Measures to reduce or eliminate releases from intentional production and use 

Article 4 Register of specific exemptions 

Article 5 Measures to reduce or eliminate releases from unintentional production 

Article 6 Measures to reduce or eliminate releases from stockpiles and wastes 

Article 7 Implementation plans 

Article 8 Listing of chemicals in Annexes A, B, and C 

Article 9 Information exchange 

Article 10 Public information, awareness, and education 

Article 11 Research, development, and monitoring 

Article 12 Technical assistance 

Article 13 Financial resources and mechanisms 

Articles 14–30 Interim financial arrangements; reporting; effectiveness evaluation; noncompliance; settlement of disputes; conference of the parties; secretariat; amendments to the Convention; adoption and amendment of annexes; right to vote; 

signature; ratification, acceptance, approval or accession; entry into force; 

reservations; withdrawal; depository; authentic texts 

Annex A Chemicals listed for elimination 

Annex B Chemicals listed for production and use restrictions 

Annex C Unintentionally produced POPs, source categories, and control measures 

Annex D Information requirements and screening criteria 

Annex E Information requirements for the risk profile 

Annex F Information on socio-economic considerations 

standing of POPs problems requires a movement 

beyond standard considerations of timing, 

causes, and effects of pollution. The evaluation 

must also consider the peculiar impacts of extremes of persistence, bioaccumulation, toxicity, 

and long-range environmental transport. 

❊ POPs pesticides are still being produced: 

From the United States' perspective, the 

listed POPs pesticides (all organochlorines) are 

generally considered "dinosaur" chemicals from 

a bygone era whose production has ceased. 

They have been superseded by more carefully 

tailored, selective, and less persistent and 

bioaccumulative alternatives. These alternatives, although in some cases potentially more 

acutely toxic to applicators (e.g., some organophosphates), are usually less prone to inducing pest resistance, lead to fewer secondary 

pest infestations, and result in less food contamination. But, as the UNEP POPs negotiations demonstrated, on a world scale POPs 

are not gone, with many still being produced 

and used, especially in developing countries. 

A number of factors, principally economic, 

contribute to this continuing use. Organochlorine pesticides are often cheap, easy to produce, and off-patent. Their persistence contributes to their perceived economic benefit, 

because one application of chlordane 

termiticide or DDT insecticide can last much 

longer than modern alternatives. Finally, 

1-12 

Genesis of the Global POPs Treaty 

some organochlorine pesticides are also perceived to exhibit lower acute mammalian 

toxicity, and are applied in developing countries with less emphasis on training and expensive protective equipment for applicators. 

❊ All POPs are not the same: Although the 12 

priority substances exhibit similar high to 

extreme measures for persistence, bioaccumulation, toxicity, and long-range transport, 

there is large variability in other physical properties. Values for volatility, solubility, and 

Henry’s Law constant (water-air partition 

coefficient, important for air transport modeling) vary by up to 5 orders of magnitude between substances (100,000-fold). A consequence is that not all POPs are expected to 

exhibit the same propensity for global distillation (Wania and Mackay, 1996). 

❊ POPs concentrations are higher near their 

sites of release: The focus on a global POPs 

convention and transboundary pollution should 

not obscure the reality that the highest POPs 

concentrations are generally found close to the 

sites of release. Problems in the United 

States are generally homegrown. This proximity does not negate the importance of international action, but emphasizes the need for 

care in determining appropriate actions. For 

example, POPs levels in marine mammals in 

the lower 48 United States are often much 

higher than those found in Alaska. However, 

marine mammals constitute a dietary staple in 

the subsistence lifestyle of many Alaska Natives. Their health and cultural well-being are 

threatened by substances from beyond U.S. 

borders that they neither used nor derived 

benefit from and yet now contaminate their 

environment. 

❊ Low concentrations in remote locations do 

not preclude a substance being a POP: 

Concentrations in remote locations reflect a 

combination of POPs parameters, emission 

levels, and accumulation time. For a substance such as endrin, an isomer of dieldrin, 

the relatively low concentrations found at long 

range are principally a result of the lower 

historic use levels in temperate climates. 

Endrin has POPs parameters similar to dieldrin, so any increased use of endrin as a substitute for dieldrin would be expected to lead to 

similar long-range risks. 

❊ Contemporaneous appraisals of pollution 

cause and effect are insufficient: Often when 

we think of environmental pollution we equate 

contemporary emissions with contemporary 

concentrations and effects on those exposed. 

These assumptions do not hold for POPs and 

must be modified by a more detailed examination of the science underlying POPs 

properties. 

– 	 Cumulative dose measures are preferable. The long environmental and biological half-lives of POPs result in a cumulative 

dose, where current tissue concentrations 

are a modified sum of past exposures. For 

persistent chemicals, tissue-concentration 

metrics that integrate dose, rather than 

daily dose measures, should be used to 

assess toxic risk (unless daily dose is interpreted consistent with half-life considerations). 

– 	 Concentrations will build up for decades. 

As a result of cumulative exposure, it is 

incorrect to assume that if a pesticide has 

been used for several years at a consistent 

level, then the concentrations now in the 

environment represent the peak or worstcase scenario. Persistence values for many 

of the POPs may be of such duration that, 

at a steady use rate, environmental concentrations could continue increasing for 

more than a century. Thus, actions to 

assess impacts and reduce use must be 

guided by predicted concentrations at the 

end of the accumulation cycle. 

– 	 Momentum. Solving POPs pollution problems takes time. These substances persist 

and recycle in the environment, potentially 

moving long distances. For those environments and peoples at the receiving end of 

this migration—e.g., sinks such as the 

1-13 

Genesis of the Global POPs Treaty 


Arctic—cessation of release at the source 

may not end POPs accumulation, which 

will take considerably longer. 

– 	 The world of the future will be different. 

We must look beyond the world of the 

present and to the future when evaluating 

potential long-term benefits of the 

Stockholm Convention. As illustrated in 

Chapter 8, the world of the future will 

have higher population levels (Figure 1-12), 

increased industrial activity, and chemical 

development and production concentrated 

in what are now developing countries. A 

central consideration should be the future 

POPs emissions potential and impact on 

the United States from these countries, if 

unconstrained by an implemented 

Stockholm Convention. 

❊ A toxic legacy of POPs at birth. Growing 

embryos and newborns of all species undergo extremely complex developmental 

changes to reach their peak performance 

potential (Figure 1-13), necessary to survive in a competitive and often dangerous 

world. This period of development is protected by biological defenses developed 

over eons of evolution, from maternal 

detoxification and placental barriers to the 

rich nutrients and proteins in mother's 

milk. POPs thwart these barriers through 

their resistance to metabolism, passage 

across biological membranes facilitated by 

their relatively low molecular weight, and 

high lipid solubility leading to concentration 

in body fats. The high energy demands of 

growth and development are also best 

satisfied through high-fat-content milk, the 

ideal POPs dosing mechanism. Indeed, 

through lactation and nursing her young, a 

female mammal can purge herself of POPs 

by transfering the lipophilic (i.e., fatsoluble) substances to her offspring. Toxic 

effects during sensitive periods of development have not been adequately studied. 

Millions 

FSU = Former Soviet Union 

ROW = Rest of World 

Figure 1-12. World population growth projections. 

1-14 

Genesis of the Global POPs Treaty 

Figure 1-13. Normal four-month human fetus, in utero ultrasound image. 

Photo: B. Rodan 

All too often, scientists and regulatory 

agencies must account for risks to the 

newborn by relying on data derived from 

adult animals or limited reproductive and 

physical development studies in rodents. 

References 

AEA. 1995. Prioritisation Criteria for the Selection of 

Persistent Organic Pollutants — A Comparison of Selection Schemes. AEA Technology, National Environmental 

Technology Center, UK. 

AEA. 1996. A Concise Review of the Development by 

the PWG/POPs of the Criteria and Procedure Recommended for Priority Substance Identification. AEA Technology, National Environmental Technology Center, UK. 

Beyer WN, Heinz GH, Redmon-Norwood AW, eds. 

1996. Environmental Contaminants in Wildlife: 

Interpreting Tissue Concentrations. SETAC Special 

Publications Series. Boca Raton, FL: CRC Press, Lewis 

Publishers. 

Carson R. 1962. Silent Spring. Boston: Houghton 

Mifflin. 

Guillette LJ Jr, Brock JW, Rooney AA, Woodward AR. 

1999. Serum concentrations of various environmental 

contaminants and their relationship to sex steroid concentrations and phallus size in juvenile American alligators. 

Arch Environ Contam Toxicol 36(4):447-455. 

Herxheimer K. 1899. Chloracne. Munchenere Med 

Wochenschr 46:278. 

Jensen J, Adare K, Shearer R. 1997. Canadian Arctic 

Contaminants Assessment Report. Department of Indian 

Affairs and Northern Development. Ottawa, Canada. 

Jones PD, Hannah DJ, Buckland SJ, Day PJ, Leathem 

SV, Porter LJ, Auman HJ, Sanderson JT, Summer C, 

Ludwig JP, Colborn TL, Giesy JP. 1996. Persistent 

synthetic chlorinated hydrocarbons in albatross tissue 

samples from Midway Atoll. Environ Toxicol Chem 

15(10):1793-1800. 

1-15 

Genesis of the Global POPs Treaty 


Klecka G, Boethling B, Franklin J, Grady L, Graham D, 

Howard PH, Kannan K, Larson RJ, Mackay D, Muir D, 

van de Meent D, eds. 2000. Evaluation of Persistence 

and Long-Range Transport of Organic Chemicals in the 

Environment. Pensacola, FL: SETAC Press. 

Ritter L, Solomon KR, Forget J, Stemeroff M, O'Leary 

C. 1995. An Assessment Report on DDT-Aldrin-Dieldrin-Endrin-Chlordane-Heptachlor-HexachlorobenzeneMirex-Toxaphene-Polychlorinated Biphenyls-Dioxins and 

Furans. For the International Programme on Chemical 

Safety (IPCS) within the framework of the Inter-Organization Programme for the Sound Management of Chemicals (IOMC): http://irptc.unep.ch/pops/indxhtms/ 

asses0.html. 

United Nations. 1993. Agenda 21: Programme of 

Action for Sustainable Development. Rio Declaration on 

Environment and Development, 1992. Final Text of 

Agreements Negotiated by Governments at the United 

Nations Conference on Environment and Development 

(UNCED), 3–14 June, 1992, Rio de Janeiro, Brazil. 

United Nations Department of Public Information, New 

York. 

U.S. Environmental Protection Agency. 1995. Great 

Lakes Water Quality Initiative Technical Support Document for the Procedure to Determine Bioaccumulation 

Factors. Office of Water. EPA/820/B-95-005. 

U.S. Environmental Protection Agency. 1999. Fact 

Sheet. Polychlorinated Biphenyls (PCBs) Update: Impact 

on Fish Advisories. Office of Water. EPA-823-F-99-019. 

Wania F, Mackay D. 1996. Tracking the distribution of 

persistent organic pollutants. Environ Sci Technol 

30:390A-396A. 

1-16 

Chapter 2 Profiles of the POPs

The scientific literature on persistent organic 

pollutants (POPs) is voluminous, complex, and 

intriguing. These are some of the most researched 

chemicals in existence, yet that research has served 

to stimulate even more investigation, down to their 

effects on the intricacies of DNA replication control 

and cellular differentiation. With this as the backdrop, this chapter seeks to demystify what these 

chemicals are, why they were developed, what they 

do, what was discovered about their toxic effects, 

and why they are the focus of global action. 

Twelve substances or substance groups are initially included under the Stockholm Convention on 

Persistent Organic Pollutants (Table 2-1). These 

POPs all exhibit the properties of prolonged environmental persistence, bioaccumulation, toxicity, 

and the potential for long-range environmental 

transport (see Chapter 9). They can be divided 

into three general categories of pesticides, industrial chemicals, and unintentional byproducts. Several of the POPs occur under more than one category, such as hexachlorobenzene, which has been 

used as a fungicide and an industrial feedstock and 

product, and is also emitted as an unintentional 

byproduct from incineration and the manufacture 

of other pesticides. Several of the substances 

represent groups of chemicals with similar structures and properties, namely the congener families 

of polychlorinated dioxins and furans, polychlorinated biphenyls (PCBs), and the mixed chlorinated 

camphenes (toxaphene). 

This chapter provides a narrative introduction to 

each of the POPs. To avoid repetition, narratives 

are combined for similar chemical groups, such as 

the cyclodiene pesticides and polychlorinated dioxins and furans. More detailed information can be 

found from a variety of federal databases and texts, 

examples of which are included in an appendix at 

the end of this chapter. Each chemical description includes a table of technical and numerical 

data on the POP. These tabular data categories, 

an explanation of their relevance to understanding the chemical’s potential environmental impact, and the information sources (unless otherwise specified in the table) are as follows: 

❊ Chemical information and structure (Klecka et 

al., 2000; a subset of chemical structure drawings is used with permission of SETAC). Representative examples are provided for substance groups where physical, chemical, and 

biological properties vary between members of 

the substance group. 

❊ Environmental persistence estimates, recognizing the wide variability of these parameters in 

different physical environments (i.e., light, 

temperature, moisture, bacteria, etc.) (Klecka 

et al., 2000). 

❊ Chemical properties important for evaluating 

the potential for long-range environmental 

transport, such as the vapor pressure and the 

air-water partition coefficient or Henry’s Law 

constant, which measures the pressure in air 

over the concentration in water at a constant 

temperature (Ritter et al., 1995). A high airwater partition coefficient indicates that movement of the chemical is facilitated to the vapor 

phase, increasing the likelihood that it can 

undergo long-range transport in the atmosphere. 

❊ Bioaccumulation, through both the octanolwater partition coefficient (equilibrium concentration in an n-octanol solution over the concentration in contiguous water; Klecka et al., 2000) 

and measured estimates from fish species 

(summarized in Rodan et al., 1999; whole 

body lipid-adjusted to 5%). 

2-1 

Profiles of the POPs 

Table 2-1. The 12 POPs under the Stockholm Convention and their current U.S. status 

POP 2001 Status for Production and/or Emissions under TSCA,a FIFRA,b CAA,c and CWAd,e 

Aldrin ❊ No registrations, most uses canceled in 1969, all uses by 1987 

❊ No production, import, or export 

❊ All tolerances on food crops revoked in 1986 

❊ Priority toxic pollutant under the CWA 

Chlordane ❊ No registrations, most uses canceled in 1978, all uses by 1988 

❊ No production (stopped in 1997), import, or export 

❊ All tolerances on food revoked in 1986 

❊ Regulated as a hazardous air pollutant (CAA) 

❊ Priority toxic pollutant under the CWA 

Dichlorodiphenyl­ ❊ No registrations, most uses canceled in 1972, all uses by 1989 

trichloroethane ❊ No production, import, or export 

(DDT) ❊ All tolerances on food and feed crops revoked in 1986 

❊ The metabolite DDE regulated as a hazardous air pollutant (CAA) 

❊ DDT, p,p’-DDE, and p,p’-DDD priority toxic pollutants under the CWA 

Dieldrin ❊ No registrations, most uses canceled in 1969, all uses by 1987 

❊ No production, import, or export 

❊ All tolerances on food crops revoked in 1986 

❊ Priority toxic pollutant under the CWA 

Endrin ❊ No registrations, most uses canceled in 1979, all uses by 1991 

❊ No production, import, or export 

❊ Priority toxic pollutant under the CWA 

Heptachlor ❊ Most uses canceled by 1978, registrant voluntarily canceled use to control fire 

ants in underground cable boxes in early 2000 

❊ No production (stopped in 1997), import, or export 

❊ All tolerances on food crops revoked in 1989 

❊ Regulated as a hazardous air pollutant (CAA) 

❊ Heptachlor and heptachlor epoxide priority toxic pollutants under the CWA 

Hexachlorobenzene ❊ No registrations as a pesticide, all uses canceled by 1985 

(HCB) ❊ No production, import, or export as a pesticide 

❊ Production and use as a closed-system intermediate consistent with the Stockholm Convention 

❊ Regulated as a hazardous air pollutant (CAA) 

❊ Priority toxic pollutant under the CWA 

Mirex ❊ No registrations, all uses canceled by 1977 

❊ No production, import, or export 

❊ Recommended nonpriority toxic water pollutant (U.S. EPA, 1999)f 

Polychlorinated ❊ No manufacture and new use prohibited in 1978 (TSCA) 

biphenyls (PCBs) ❊ Regulated as a hazardous air pollutant (CAA) 

❊ Priority toxic pollutant under the CWA 

Polychlorinated ❊ As a contaminant in production, regulated under TSCA and FIFRA 

dibenzo-p-dioxins ❊ Hazardous air pollutant and emission standards regulated under the CAA 

(dioxins) ❊ 2,3,7,8-TCDD a priority toxic pollutant under the CWA 

Polychlorinated ❊ As a contaminant in production, regulated under TSCA and FIFRA 

dibenzofurans ❊ Hazardous air pollutant and emission standards regulated under the CAA 

(furans) 

Toxaphene ❊ No registrations, most uses canceled in 1982, all uses by 1990 

❊ No production, import, or export 

❊ All tolerances on food crops revoked in 1993 

❊ Regulated as a hazardous air pollutant (CAA) 

❊ Priority toxic pollutant under the CWA 

a

 Toxic Substances Control Act b

 Federal Insecticide, Fungicide, and Rodenticide Act 

c

 Clean Air Act 

d Clean Water Act 

e Effluent limits and standards for all POPs are authorized under the CWA. f

 National Recommended Water Quality Criteria-Correction. US-EPA 822-Z-99-001. Office of Water. 

2-2 

Profiles of the POPs 

❊ Acute toxicity in rats, estimated as the acute 

dose that would kill half the experimental rats 

(lethal dose 50%; LD50), noting that within 

species there is a spectrum of individual resistance to toxic effects, and that between-species LD50 values can vary to a large degree 

(Meister, 2000). 

❊ Chronic toxicity reference dose (RfD) in the 

United States, which is an estimate (with uncertainty spanning perhaps an order of magnitude) 

of a daily exposure to the human population 

(including sensitive subgroups) that is likely to be 

without an appreciable risk of deleterious effects 

during a lifetime. The RfD is based on experimental or epidemiologically determined doses at 

which there is no statistically or biologically 

significant indication of toxic effects. RfDs include uncertainty factors to account for animalto-human interspecies differences, variability 

between humans, and database deficiencies 

(www.epa.gov/IRIS). 

❊ History of production and use in the United 

States, providing a brief summary of historical 

manufacturing data, years during which these 

activities occurred, and when they were curtailed 

and ultimately ceased (UNEP, 2000). 

❊ International production and use, summarizing 

data collected by the United Nations Environment Programme (UNEP) during the POPs 

negotiation and from national requests for 

chemical-specific use exemptions under the 

Stockholm Convention (UNEP, 2000). 

1. Intentionally Produced POPs: 

Pesticides 

The nine pesticide POPs were introduced into 

commercial use after World War II and dramatically 

changed modern pest control. These compounds 

were effective against a wide range of pests, often 

for extended periods of time. Ironically, the chemical property of long environmental persistence that 

enhanced the pesticides' efficacies also increased 

their environmental destructiveness. Repeated 

applications of the pesticide POPs (Figure 2-1) led 

to widespread contamination, impacts on nontarget species, and residues in foods. 

Figure 2-1. Aerial spraying of pesticides on crops. 

Photo: U.S. EPA 

Cyclodiene Insecticides 

Aldrin, dieldrin, endrin, chlordane, heptachlor, 

and mirex are all cyclodiene organochlorine insecticides. They are highly persistent compounds, exhibiting especially high resistance to 

degradation in soil. Aldrin, dieldrin, and particularly endrin exhibit high acute mammalian toxicity (oral LD50s between 7 and 90 mg/kg); chlordane, heptachlor, and mirex are moderately 

acutely toxic (oral LD50s between 100 and 400 

mg/kg) (Meister, 2000). Due to the persistence 

of these insecticides, surface application on food 

crops proved problematic because residues remained on produce after harvest. The cyclodienes were, however, widely used as soil insecticides in the United States, particularly against 

termites and soil-dwelling insects that attack the 

roots of crop plants. Although the agricultural 

uses of the cyclodienes were cancelled by the 

EPA during the 1970s, they continued to be used 

under restricted conditions as termiticides well 

into the 1980s (Ware, 1989). 

Aldrin, dieldrin, and endrin are extremely similar 

chemically, the latter two being stereoisomers of 

each other (Tables 2-2, 2-3, and 2-4). Aldrin is 

rapidly transformed into dieldrin both in air and in 

soil (Glotfelty, 1978; Gannon and Bigger, 1958). 

Endrin was used initially as a general insecticide, 

particularly on nonfood crops such as cotton and 

tobacco. It also served as an avicide (bird-killing 

agent) and rodenticide, exploiting its high toxicity 

2-3 

Profiles of the POPs 

Table 2-2. 

Chemical number: 

information Molecular formula: 12H8Cl6 

Molecular weight: 364.92 

Persistence lf-lives: 

~1.1–3.4 years (water) 

~1.1–3.4 years (soil) 

Properties related to Henry’s law constant: 4.96 x 10–4 atm-m3/mol at 25o

C 

environmental transport Vapor pressure: 2.31 x 10-5 mm Hg at 20o

C 

Solubility in water: oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 106.5 

BAF/BCF ~ 6100 

Acute toxicity Oral LD50 = 38-67 mg/kg 

Dermal LD50 = 98 mg/kg 

Chronic toxicity Reference dose (RfD) = 3 x 10-5 mg/kg/day (UF = 1000) 

US production Years produceda

: 1948-1974 

history Peak usage in 1966b

: 8,600 tonnes (19 million lbs) 

No present production, import, or export in USA 

US use history – Insecticide on cotton, citrus, and corn crops 

– Termiticide 

All uses canceled by 1987 

Current (2001) – No known current producers 

international production – Reported use as an ectoparasiticide in one country 

and reported use 

a

Sittig, 1985. 

b

ATSDR, 1993a. 

Cl 

Cl 

Cl 

Cl 

Cl2 

Aldrin 

309-00-2 

C 

< 0.4 days (air) 

17-180 μg/L at 25 

CAS 

Ha

K

to vertebrates. Aldrin and dieldrin, which were 

inexpensive to manufacture, were produced in 

large quantities in the United States during the 

1960s and used most frequently as insecticides to 

control soil pests affecting corn and citrus crops, as 

well as termites in buildings and other structures. 

The long persistence of dieldrin (whether from 

initial dieldrin formulations or from aldrin formulations) and its acute toxicity to nontarget wildlife 

led to environmental concerns, particularly after 

numerous mass bird deaths were associated with 

the use of dieldrin as a seed treatment (Beyer et 

al., 1996). However, long before regulatory actions to restrict or cancel these insecticides were 

instigated, technical problems had emerged because of their broad-spectrum toxicity and long 

persistence. The production and uses of aldrin, 

dieldrin, and endrin declined significantly by the 

mid-1970s in the United States, due in large part 

to the development of resistance in target pests 

(Ware, 1989) and problems with secondary pest 

upsets caused by the elimination of natural predators (DeBach and Rosen, 1991). The development of other pesticides (organophosphates, 

carbamates, synthetic pyrethroids and, more 

recently, insect growth regulators) that were considered more effective and less environmentally 

destructive also reduced demand for the cyclodiene insecticides (ATSDR, 1993a). 

Aldrin was also produced and widely used overseas, 

particularly for the control of cotton pests and 

termites, until human health and environmental 

concerns led to bans in many countries (Pearce, 

1997). Dieldrin was initially used for indoor house 

spraying to control mosquitoes that carry malaria, 

but it is no longer used or recommended by the 

World Health Organization (WHO) because of its 

high mammalian toxicity and resistance problems 

among many target mosquitoes (Rozendaal, 1997; 

Shidrawi, 1990). Dieldrin was also donated to 

African countries until the late 1980s to control 

plagues of migratory locusts, creating numerous 

2-4 

Profiles of the POPs 

Table 2-3. 

Chemical number: 

information formula: 12H8Cl6O 

Molecular weight: 380.92 

Persistence Half-lives: 

~1.1–3.4 years (water) 

~1.1–3.4 years (soil) 

Properties related to Henry's law constant: 5.8 x 10–5 atm-m3/mol at 25o

C 

environmental transport Vapor pressure: 1.78 x 10-7 mm Hg at 20o

C 

Solubility in water: oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 105.2 

BAF/BCF 

Acute toxicity Oral LD50 = 37-87 mg/kg 

Dermal LD50 = 60-90 mg/kg 

Chronic toxicity Reference dose (RfD) = 5 x 10-5 mg/kg/day (UF = 100) 

US production Years produceda

: 

history Peak US usage in 1966b

: 455 tonnes (1 million lbs) 

No present production, import, or export in USA 

US use history – Insecticide control on cotton, citrus, and corn crops 

– Termiticide 

All uses canceled by 1987 

Current international – No known current producers 

production and use – Insecticide used until 1980s for control of plague locusts. No current uses 

except for agricultural operations in one country (for 2 years to exhaust existing 

stocks) a

 Sittig, 1985. 

b ATSDR, 1993a. 

Cl 

Cl2 O 

Cl 

Cl 

Cl 

Dieldrin 

60-57-1 

C 

~1.3–4.2 days (air) 

140 μg/L at 20 

~ 920,000 

1948 – 1974 

CAS 

Molecular 

K

stockpiles of obsolete chemicals that remain an 

environmental hazard in many countries (FAO, 

1998) (Figure 2-2). Newer pesticides, including 

phenylpyrazole compounds, are now available 

Figure 2-2. Obsolete drums of dieldrin, previously used 

for locust control, Morocco. 

Photo: Janice Jensen 

for locust control, although the economic costs 

and environmental damage associated with these 

large-scale pesticide applications suggest that 

information-based integrated pest management 

approaches using less total pesticide are more 

appropriate locust control strategies (Showler and 

Potter, 1991). 

Chlordane, heptachlor, and mirex were used 

extensively in the United States in the 1950s 

and 1960s for the control of soil insects in agricultural crops, and for termites and other structural pests in buildings (Figure 2-3). Chlordane 

and heptachlor have very similar chemical structures (Tables 2-5 and 2-6). Chlordane was 

manufactured and used as a complex mixture of 

related compounds (cis- and trans-chlordane, 

heptachlor, nonachlor, plus many lesser compounds), often referred to as technical chlordane 

(Sovocool et al., 1977). It was often applied 

2-5 

Profiles of the POPs 

Table 2-4. 

Chemical number: 

information Molecular formula: C12H8

Cl6O 

Molecular weight: 380.92 

Persistence Half-livesa

: 

~1.0–4.1 years (water) 

~4–14 years (soil) 

Properties related to Henry's law constantb

: 6.36 x 10–6 atm-m3/mol at 25oC 

environmental transport Vapor pressure: 7 x 10-7 mm Hg at 25o

C 

Solubility in water: oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 105.2 

BAF/BCF ~ 7,000 

Acute toxicity Oral LD50 = 7-15 mg/kg 

Dermal LD50 = 15 mg/kg (female) 

Chronic toxicity Reference dose (RfD) = 3 x 10-4 mg/kg/day (UF = 100) 

US production Years producedc

: 

history Peak US usage in 1962d

: Estimated 2270–4545 tonnes (5 to 10 million lbs) 

No present production, import, or export in USA 

US use history – Insecticide on cotton crops 

– Rodenticide in orchards 

– All uses canceled by 1991 

Current international – No known current producers 

production and use – No current use reported a

Air: 

Soil: Menzie, 1972; HSDB, 1997. 

b

HSDB, 2002. 

c

ATSDR, 1996a. d

IARC, 1974. 

Cl 

Cl 

Cl 

Cl 

O Cl2

Endrin 

72-20-8 

~2.2 days (air) 

220-260 μg/L at 25 

1951-1986 

HSDB, 2002; Burton and Pollard, 1974. Water: Sharom et al., 1980; Callahan et al., 1979.

CAS 

K

directly to soil to create a chemical barrier 

against subterranean termites, frequently remaining effective for 25 years or more in temperate 

areas (Grace et al., 1993). Heptachlor was 

applied both directly to soil and seeds for agriculFigure 2-3. Subterranean worker termites, a target of 

chlordane and some other POPs pesticides. 

Photo: Clemson University Cooperative Extension Service - USDA joint 

project 

tural uses and to wood for termite protection 

(ATSDR, 1993b). Heptachlor is converted in the 

environment to heptachlor epoxide, prolonging 

its persistence and toxicity. The last registered 

use for heptachlor in the United States, now 

cancelled, was as an insecticide in small containers placed in cable boxes in the southeast to 

prevent nest building by fire ants in electrical 

equipment. Registered chlordane uses in the 

United States were cancelled by 1988 in response to evidence of human exposure through 

accumulation of chlordane in fat, and human 

cancer risks based on animal bioassay results. 

Both chlordane and heptachlor are still used in 

several African, Asian, and Eastern European 

countries for termite control (UNEP, 2000). 

Mirex, structurally similar to the now deregistered 

cyclodiene insecticide chlordecone (Kepone), was 

produced in smaller quantities and used for ant 

control, often in the form of a bait (Table 2-7). 

Mirex was also used in the United States as a 

fire retardant additive (U.S. EPA, 1998). 

2-6 

Profiles of the POPs 

Table 2-5. dane 

Chemical number: 

information formula: 10H6Cl8 

Molecular weight: 409.78 

Persistence Half-lives: 

~1.1–3.4 years (water) 

~1.1–3.4 years (soil) 

Properties related to Henry's law constant: 4.8 x 10–5 atm-m3/mol at 25o

C 

environmental transport Vapor pressure: 1 x 10-6 mm Hg at 20o

C 

Solubility in water: 56 μg/L at 25oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 106 

BAF/BCF ~ 250,000 

Acute toxicitya Oral LD50 = 283 mg/kg 

Dermal LD50 = 580 mg/kg (rabbit) 

Chronic toxicity Reference dose (RfD) = 5 x 10-4 mg/kg/day (UF = 300) 

US production Years producedb

: 1946 – 1997 

history Average annual US usage prior to 1983b

: >1600 tonnes (3.6 million lbs) 

No present production, import, or export in USA 

US use history – Insecticide in agriculture and home gardens 

– Termiticide 

– All uses canceled by 1988 

Current (2001) – China, Singaporec 

international – Chlordane is still used in a number of countries in Africa and Asia, 

production and use primarily as a termiticide a

Ware, 1989. b

EPA, 1998. c

The basic producers are Sino Agro-Chemical Industry Ltd. (China) and Agsin Pte. Ltd. (Singapore) (Meister, 

2000). 

Chlor 

57-74-9 

C 

~1.3–4.2 days (air) 

CAS 

Molecular 

K 

A number of alternative chemical control strategies can now be used effectively to replace the 

cyclodienes, although most do not exhibit the 

same persistence in soil. These include longacting organophosphate pesticides and several 

synthetic pyrethroids (Mauldin et al., 1987; Su et 

al., 1993; Kard, 1996). Nonchemical alternatives, such as physical barriers and heat treatment, can provide effective and less toxic termite control in buildings (Grace and Yates, 1999; 

Pearce, 1997; Woodrow and Grace, 1998). 

Dichlorodiphenyl trichloroethane (DDT) 

DDT was the first organochlorine insecticide developed, and is probably the most famous and 

controversial pesticide ever made. Worldwide, an 

estimated 2 million tons have been produced and 

applied since 1940, primarily in agriculture (Table 

2-8) (Ware, 1989; ATSDR, 2000). Unlike many 

of the other synthetic organic pesticides developed 

later, DDT exhibited relatively low mammalian 

toxicity, was initially highly effective at controlling 

a variety of insect pests, and, perhaps most importantly, was very inexpensive to produce. This 

unique combination of properties led to DDT’s 

widespread use in public health, beginning with 

the control of louse-borne typhus during World 

War II. DDT was a central tool in the malaria 

eradication programs of the 1950s and 1960s 

(Figure 2-4). Although the malaria eradication 

goal proved elusive in much of the tropical world, 

DDT nonetheless contributed to improved health 

and saved countless lives in many malarious countries (Oaks et al., 1991). 

In the United States, malaria had been largely 

eradicated prior to the introduction of DDT, although DDT was widely used for nuisance mosquito control. The primary use of DDT was as a 

broad-spectrum insecticide on agricultural crops, 

principally cotton (~90% of total use), but also on 

potatoes, corn, tobacco, and apples, and against 

2-7 

Profiles of the POPs 

Table 2-6. 

Chemical CAS number: 76-44-8 

information Molecular formula: C10H5Cl7 

Molecular weight: 373.32 

Persistence Half-lives: ~1.3–4.2 days (air) 

~0.03–0.11 years (water) 

~0.11–0.34 years (soil) 

Properties related to Henry's law constant: 2.3 x 10–3 atm-m3/mol 

environmental transport Vapor pressure: 3 x 10-4 mm Hg at 20o

C 

Solubility in water: 180 μg/L at 25oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 105.27 

BAF/BCF ~ 8,500 

Acute toxicity Oral LD50 = 147-220 mg/kg 

Dermal LD50 > 2000 mg/kg (rat); 119-320 mg/kg (rabbit) 

Chronic toxicity Reference dose (RfD) = 5 x 10-4 mg/kg/day (UF = 300) 

US production Years produceda

: 

history No present production, import, or export in USA 

US use history – Termiticide 

– Insecticide for control of fire ants in underground cable boxes 

– Most uses canceled by 1978, all uses canceled 2000 

Current (2001) – No known current producers, although an exemption has been requested for 

international use as a pesticide and pesticide solvent 

production and use – Insecticide for control of termites and other soil insects by several 

countries 

– Solvent in pesticides by two countries a

ATSDR, 1993b; EPA Office of Pesticide Programs. 

Heptachlor 

1953-1997 

K 

forest pests (Ware, 1989; U.S. EPA, 1998; 

ATSDR, 2000). DDT use in the United States 

peaked in 1961, but began to decline thereafter 

because of several technical complications. One 

Figure 2-4. 

target of DDT. 

Photo: WHO/TDR/Gwadz 

Anopheles mosquito, vector of malaria and 

problem was mounting resistance, as continual 

exposure to the heavily used and persistent 

chemical selected for resistant insects. DDT 

resistance was observed in apple pests as early 

as 1954 (Cutright, 1954). By 1984, DDT resistance was documented in 233 species of insects 

and mites worldwide, including many important 

agricultural pests (Georghiou, 1986). DDT’s 

broad spectrum of activity against virtually all 

insects, pests and beneficials alike, and its long 

environmental persistence also led to serious 

secondary pest problems. Secondary pests are 

normally suppressed by natural predators, but 

their populations spiral upward out of control 

when the predators are killed by DDT. For example, an important pest of California citrus, the 

cottony cushion scale, was controlled by the 

Vedalia beetle until growers in 1946 applied 

DDT to control a different pest (Figure 2-5). 

The DDT applications killed off the predator but 

not the white-colored scale, whose populations 

2-8 

Profiles of the POPs 

Table 2-7. ex 

Chemical number: 

information formula: 10Cl12 

Molecular weight: 545.5 

Persistence f-lives: ~4.2–12.5 days (air) 

~0.34–1.14 years (water) 

> 3.4 years (soil) 

Properties related to Henry's law constanta

: 8.3 x 10–3 atm-m3/mol at 20oC 

environmental transport Vapor pressure: 3 x 10-7 mm Hg at 25o

C 

Solubility in watera: 5.45 x 10-5 μg/L at 25oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 106.9 

BAF/BCF ~ 2,400,000 

Acute toxicity Oral LD50 = 306 mg/kg 

Dermal LD50 = 800 mg/kg (rabbit) 

Chronic toxicity Reference dose (RfD) = 2 x 10-4 mg/kg/day (UF = 300) 

Past production in Years producedb

: 

USA Total US production ~1500 tonnes (3.3 million lbs). Peak US usage between 

1963 and 1968c

. 

No present production, import, or export in USA 

History of use(s) in USA – Insecticide for fire ant control 

– Industrial fire retardant additive 

All pesticide uses canceled by 1977 

Current (2001) No known current producers. 

international for termiticide manufacture 

production and use An exemption has been requested by two countries for use in termite 

control a

AMAP, 1998. b

EPA, 1998. c

EPA, 1998. otal is for Hooker Chemical Company only. wo other US companies also manufactured mirex 

during this time. 

Mir 

2385-85-5 

C 

1954-1976 

China has requested a production exemption 

T 

CAS 

Molecular 

Hal

K 

T 

exploded, covering trees so densely the orchards 


looked snow-covered. The Vedalia beetle had to 


be reintroduced at a cost of up to $1 per beetle 


Figure 2-5. Vedalia beetles, a nontarget species killed by 

DDT, eating cottony cushion scale. 

Photo: J.K. Clark, University of California IPM project 

to regain control of the scale (DeBach and 

Rosen, 1991). 

At the same time that DDT use peaked in the 

1950s and 1960s, there was mounting evidence 

of the environmental impacts from DDT and its 

long-lived metabolites, DDE and DDD (Ratcliffe, 

1967; Wurster et al., 1965; Riseborough, 1972). 

These DDT, DDE, and DDD concentrations are 

often added together and reported as sum-DDT, 

s-DDT, or (-DDT values. Their impacts were 

particularly severe on bird populations through 

eggshell thinning and chick mortality in raptors 

(e.g., bald eagles, falcons) and oceanic birds 

(e.g., pelicans) (Beyer et al., 1996) (Figure 2-6). 

Although DDT was considered to exhibit relatively low acute mammalian toxicity, concerns 

were being expressed about potential chronic 

reproductive impacts on humans (O’Leary et al., 

2-9 
Profiles of the POPs 

Table 2-8. 

Chemcial CAS number: 

information Molecular formula: 14H9Cl5 

Molecular weight: 354.49 

Persistence Half-lives: 

~0.34–1.14 years (water) 

~1.1–3.4 years (soil) 

Properties related to Henry's law constant: 1.29 x 10–5 atm-m3/mol at 23o

C 

environmental transport Vapor pressurea

: 1.6 x 10-7 mm Hg at 20oC 

Solubility in water: oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 106.19 

BAF/BCF ~ 1,800,000 

Acute toxicity Oral LD50 = 87 mg/kg 

in mammalsb Dermal LD50 = 1,931 mg/kg (rabbit) 

Chronic toxicity Reference dose (RfD) = 5 x 10-4 mg/kg/day (UF = 100) 

US production Years producedb,c: 1940 – (none by 1993) 

history Peak US production in 1962c

: 82,000 tonnes (180 million lbs) (Metcalf, 1995) 

No present production, import, or export in USA. 

Contaminant of the pesticide dicofol. 

US use history – Broad spectrum insecticide on many crops 

– Most uses canceled by 1972. All uses canceled by 1989 

Current (2001) Production: China, India 

international production Insecticide used in at least 25 countries for control of insect vectors of human 

and use disease, particularly malaria. Used in the production of dicofol. a

HSDB, 2002. 

b

Ware, 1989. 

c

EPA, 1998. 

DDT 

50-29-3 

C 

~4.2–12.5 days (air) 

1.2-5.5 μg/L at 25 

K

1970; Saxena et al., 1981; Wassermann et al., 

1982). Subsequent information has shown p,p’-

DDE, a DDT metabolite, to bind to the androgen 

receptor, antagonizing androgen action (Kelce et 

al., 1995, 1997; Gray et al., 1999; Maness et 

al., 1998; NAS, 1999). A recently published 

human epidemiological study has demonstrated 

an association between DDT concentrations and 

increased preterm human births, a major contributor to infant mortality. Longnecker et al. 

Figure 2-6. Bird eggshell effects after population DDE 

exposure. 

Photo: US FWS 

A. Cracked shell. B. Dented shell. 

(2001) analyzed frozen maternal serum samples 

that had been collected between 1959 and 1965 

and stored as part of the U.S. Collaborative 

Perinatal Project (CPP). During this time of peak 

DDT use in the United States, the median DDE 

concentration of 25 mcg/L was several-fold 

higher than current U.S. levels. Taking into 

consideration data on potential confounding 

variables collected during this study (age, birth 

order, socioeconomic status, etc.), the association of increasing serum DDE concentrations with 

preterm birth was highly statistically significant 

(Figure 2-7, trend p<0.0001). Dose-response 

data were consistent with serum DDE levels 

above 10 mcg/L affecting the risk of preterm 

birth. These human epidemiological findings 

warrant consideration when balancing the risks of 

DDT against its benefits for malaria vector control and the costs of alternatives. 

All uses of DDT in the United States were cancelled by EPA in 1972, primarily because of 

2-10 
Profiles of the POPs 

Table 2-9. oxaphenea 

Chemical CAS number: 

information Molecular formula: C10H10Cl8 

Molecular weight: 413.82 

Persistence f-lives: ~4.2–12.5 days (air) 

>3.4 years (water) 

>3.4 years (soil) 

Properties related to Henry's law constant: 6.3 x 10–2 atm-m3/mol 

environmental transporta Vapor pressureb

: 5 x 10-6 – 0.4 mm Hg at 20oC 

Solubility in water: 550 μg/L at 20oC 

Bioaccumulation ow (octanol-water partition coefficient)c

 ~ 104.8–106.6 

BAF/BCF ~ 1,100,000 

Acute toxicity in Oral LD50 = 40 mg/kg 

mammalsd Dermal LD50 = 600 mg/kg (rabbit) 

Chronic toxicity Reference dose (RfD) = under development 

US production Years producede

: 1946-1990s 

history Peak US production in 1972b

: 21,000 tonnes (46 million lbs) 

No present production, import, or export in USA 

US use history – Insecticide to control cotton pests and plague grasshoppers and for mange 

control on cattle 

– Most uses canceled by 1982 

– All uses canceled by 1990 

Current (2001) No known producers 

international o known registered uses 

production and use 

a

Toxaphene is a complex mixture of various chlorinated bornanes and camphenes. There are discrepancies 

noted in the literature regarding physical properties; see ATSDR 1996b for details. 

b

ATSDR, 1996b. 

c

Fisk et al., 1999. 

d

Ware, 1989. 

e

EPA, 1998. 

T 

8001-35-2 

Hal

K

N

Figure 2-7. Graph of the association between maternal 

serum DDE levels and preterm birth risk. Adjusted odds 

ratios and 95% confidence intervals (from Longnecker et 

al., 2001). 

positive cancer results in rodent bioassays. DDT 

production in the United States for export occurred until at least 1985 (ATSDR, 2000). DDT 

use for disease (mostly malaria) vector control 

continues in an estimated 25 or more developing 

countries, primarily because of its low cost and 

persistence (WHO, 1999). Many other insecticides are available for indoor house spraying 

(Chavasse and Yap, 1997), but DDT’s lower cost 

remains an advantage, at least in some countries 

(Walker, 2000). Other approaches to disease 

control such as case detection and treatment, or 

pyrethroid-treated bednets, may prove more 

cost-effective and sustainable in the long term 

(Goodman et al., 1999). For the future, the 

Stockholm Convention strives for a balance 

among the public health benefits of DDT for 

malaria control, the availability and cost of alternatives, and the impacts of DDT on ecosystems 

2-11 
Profiles of the POPs 

Table 2-10. obenzene (HCB) 

Chemical CAS number: 118-74-1 

information Molecular formula: C6Cl6 

Molecular weight: 284.78 

Persistence Half-lives: 

>3.4 years (water) 

>3.4 years (soil) 

Properties related to Henry's law constant: 7.1 x 10–3 atm-m3/mol at 20o

C 

environmental transport Vapor pressure: 1.089 x 10-5 mm Hg at 20o

C 

Solubility in water: 40 μg/L at 20oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 105.5 

BAF/BCF ~ 110,000 

Acute toxicity in mammalsa Oral LD50 = 3,500 mg/kg 

Chronic toxicity Reference dose (RfD) = 8 x 10-4 mg/kg/day (UF = 100) 

US production Years produced as a fungicidea

: 1945–late 1970s 

history HCB is produced as a byproduct or contaminant of certain chemicals. 

Estimated annual US production as a byproduct or impurity range from 

68–689 tonnes (0.15–1.52 million lbs), the majority of which is destroyed 

onsite 

US use and – Fungicide for seed and wheat 

source history – Currently imported for use as an intermediate; import anticipated to cease in 

future to comply with the closed-system, site-limited exemption 

Current (2001) – No current production for fungicide applications. 

international No current reported uses as a fungicide. 

production and use – Several countries have requested exemptions as an intermediate, a closedsystem, site-limited intermediate, or contaminant in pesticides. a

ATSDR, 1996c. 

Hexachlor 

~ 417–1250 days (air) 

K

– 

and, potentially, human health. While working 

toward a goal of reducing and ultimately eliminating the use of DDT, parties may use DDT 

only for disease vector control in accordance with 

World Health Organization recommendations 

(UNEP, 2000). 

Toxaphene 

Toxaphene is a mixture of at least 670 chlorinated terpenes, produced through chlorinating 

camphene (Table 2-9; image shown is a chlorinated bornane structure). Its primary use was on 

cotton, where it was generally applied with another insecticide, first DDT and subsequently 

organophosphate insecticides such as methyl 

parathion. U.S. production of toxaphene 

peaked in 1972, when it was the most heavily 

manufactured pesticide in the country, largely as 

a replacement for DDT. Toxaphene was also 

used as a piscicide to eradicate fish species 

considered undesirable for sport fishing in 

Canada and the northern United States (U.S. 

EPA, 1998). Fish restocking efforts were sometimes difficult because of the longevity of active 

toxaphene residues, highlighting the problem of 

environmental persistence. Most registered uses 

in the United States were withdrawn in 1982, on 

the basis of studies showing tumors in toxaphene-exposed laboratory animals, evidence of 

acute toxicity to aquatic organisms, and impacts 

on nontarget animals including endangered species. 

Worldwide, toxaphene was one of the most 

widely used agricultural insecticides during the 

1960s and 1970s, primarily for control of cotton 

pests. Between 1950 and 1993, when all production ceased in the United States, an estimated 2.6 billion pounds had been manufactured 

worldwide (ATSDR, 1996b). Stockpiles of toxaphene continue to threaten the environment in 

some areas. For example, in Nicaragua, 230 

metric tonnes of toxaphene were recently reported stockpiled in a zone at high risk for earthquakes near Lake Managua, a unique ecosystem 

2-12 

Profiles of the POPs 

Table 2-11. olychlorinated Biphenyls (PCBs) 

Example: Aroclor 1254 mixture 

Chemical CAS numbera

: 11097-69-1 

information Molecular formula: 12Cl(x + y) 

Molecular weight: 328a (188.7–498.7, PCB range) 

Persistence Half-lives: 

~5.7 years (water) [PCB congener group] 

~1.14 years (soil) [PCB congener group] 

Properties related to Henry’s law constant: 2.0 x 10-3 atm-m3/mol at 25o

C 

environmental transporta Vapor pressure: 7.71 x 10–5 mm Hg at 25o

C 

Solubility in water: 57 μg/L at 24oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 106.5 

BAF/BCF ~ 3,000,000 

Acute toxicity in mammals Oral LD50 = 1,010 mg/kg 

Chronic toxicity Reference dose (RfD) = 2 x 10-5 mg/kg/day 

(UF = 300), under review 

ATSDRa chronic MRL = 0.02 mcg/kg/day (UF = 300) 

US production history Years PCBs produced: 1929–1977; banned under TSCA Section 6(e) effective 

1979 

Peak PCB production 1970, ~3900 tonnes (8.5 million pounds) annually for all 

PCBs 

No present production, import, or export in USA 

Current (2001) US source Use allowed if in certain existing equipment; environmentally sound 

and use history destruction/disposal after service life of equipment 

Current (2001) Manufacture discontinuedb 

international No recorded new uses; widespread residual use in existing equipment and 

production and use a

ATSDR, 1997. b

AMAP, 2000. 

P 

C 

~4.2 days (air) [PCB congener group] 

K

products 

and home to many rare species of wildlife 

(EARTH, 2000). 

Hexachlorobenzene 

Hexachlorobenzene (HCB) is included under all 

three general categories of POPs: as a pesticide, an industrial chemical, and an unintended 

byproduct (Table 2-10). HCB was introduced as 

a pesticide in the United States in 1945 for 

antifungal seed and soil treatment. All U.S. 

pesticide uses were canceled in 1985 (Ware, 

1989; ATSDR, 1996c). The human toxicity of 

HCB was sadly demonstrated in Turkey during 

the late 1950s, when an estimated 3,000 to 

4,000 people ingested bread inadvertently made 

from HCB-treated grain at approximately 2 kg 

HCB per 1,000 kg wheat. The HCB led to 

porphyria cutanea tarda in adults, a metabolic 

defect of blocked hemoglobin synthesis that 

causes light-sensitive skin lesions, colored urine, 

and, in some cases, death. All children born to 

porphyric mothers during this epidemic died, 

with an estimated 1,000 to 2,000 children dying 

from related skin lesions, exacerbated by the 

HCB transfer in breast milk (Peters et al., 1982, 

1987). 

Industrial uses of HCB have varied, including 

pyrotechnic coloring in military ordnance, synthetic rubber production, and as a chemical intermediate in dye manufacture and organic chemical synthesis (Bailey, 2001). There are no 

current uses of HCB as an end product in the 

United States, although it is imported for use as 

a production intermediate. An exemption is 

available under the Stockholm Convention for the 

use of HCB as a closed-system, site-limited intermediate. HCB is still produced as an unintended 

byproduct during the manufacture of chlorinated 

solvents and as an impurity of certain pesticides 

2-13 

Profiles of the POPs 

Table 2-12. olychlorinated Dibenzo-p-Dioxins 

Example: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) 

Chemical numbera: 

information Molecular formula: C12H4Cl4O2 

for TCDD Molecular weight: 322.0 

Persistence Half-lives: 

~0.11–0.34 years (water) [range for PCDDs] 

~0.34–1.1 years (soil) [range for PCDDs] 

Properties related to Henry’s law constant: 1.6 x 10–5 – 1.0 x 10–4 atm m3/mol at 25o

C 

environmental transporta Vapor pressure: 1.5 x 10–9 – 3.4 x 10–5 mm Hg at 25o

C 

Solubility in water: 0.019 μg/L at 25oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 106.9 

BAF/BCF ~ 130,000 

Acute toxicity Hamster oral LD50 = 5051 mcg/kg 

in mammalsa Rat oral LD50 = 22 – 165 mcg/kg 

Mink oral LD50 = 4.2 mcg/kg 

Guinea pig oral LD50 = 0.6 mcg/kg 

Chronic toxicity Under EPA review: www.epa.gov/ncea/dioxin.htm 

ATSDRa chronic MRL = 0.000001 mg/kg/day (UF = 100) 

Major sources Municipal and medical waste incineration 

(US and international) Open and barrel burning of waste 

Elemental chlorine bleach pulp and paper manufacture 

Certain thermal processes in the metallurgical industry 

Selected chemical manufacturing processes, e.g., 2,4,5-trichlorophenol 

production (now ceased) 

a

ATSDR, 1998. 

P 

1746-01-6 

4.2–12.5 days (air) [range for PCDDs] 

CAS 

K

(picloram, PCNB, chlorothalonil, DCPA, and 

PCP) (ATSDR, 1996c). It is also created and 

emitted during incineration practices. Due to its 

chemical structure, HCB is extremely stable, 

globally distributed, and considered among the 

most persistent of all POPs. 

2. Intentionally Produced POPs: 

Industrial Chemicals 

Polychlorinated Biphenyls (PCBs) 

PCBs are a mixture of synthetic organic chemicals with the same basic chemical structure and 

similar physical properties, ranging from oily 

liquids to waxy solids (Table 2-11). Because of 

their nonflammability, chemical stability, high 

boiling point, and electrical insulating properties, 

PCBs were used in hundreds of industrial and 

commercial applications, including electrical, 

heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; 

and in pigments, dyes, and carbonless copy paper. First manufactured in 1929, more than 1.5 

billion pounds of PCBs were manufactured in the 

United States (plus elsewhere in the world) before domestic production ceased in 1977. 

PCBs are principally addressed under the 

Stockholm Convention as intentionally produced 

industrial chemicals. PCBs are also closely linked 

to the polychlorinated dioxin and furan byproduct 

POPs for the following reasons: 

❊ Coplanar PCBs have a similar chemical structure and spatial configuration to the polychlorinated dioxins and furans, and much of the 

toxicity of all three congener groups is linked 

through a common mode of action (mediated 

through binding to the aryl hydrocarbon [Ah] 

receptor in the cell) and the concept of dioxin 

toxicity equivalence (see under byproduct 

POPs). 

2-14 

Profiles of the POPs 

Table 2-13. olychlorinated Dibenzofurans 

Example: 2,3,7,8-Tetrachlorodibenzofuran (TCDF) 

Chemical CAS numbera: 51207-31-9 

information for Molecular formula: C12H4Cl4O 

TCDF Molecular weighta: 306.0 

Persistence Half-lives: 

~0.11–0.34 years (water) [range for PCDFs] 

~1.1–3.4 years (soil) – for all furans [range for PCDFs] 

Properties related to Henry's law constanta

: 1.48 x 10–5 atm-m3/mol 

environmental transportb Vapor pressurea

: 9.21 x 10–7 mm Hg at 25oC 

Solubility in waterb: 0.692 μg/L at 26oC 

Bioaccumulation ow (octanol-water partition coefficient) ~ 106.1 

BAF/BCF ~ 61,000 

Acute toxicity in mammals See for dioxins, based on TEQ values 

Chronic toxicity Under review: www.epa.gov/ncea/dioxin.htm 

Major sources See for dioxins 

(US and international) 

a

ATSDR, 1994. 

b

HSDB, 2002. 

P 

4.2–12.5 days (air) [range for PCDFs] 

K

❊ Burning and high-temperature treatment of 

PCB mixtures can lead to the creation of 

polychlorinated dibenzofurans (PCDFs), further 

exacerbating the potential toxicity from 

PCBs. This occurred during the Yusho and 

Yu-Cheng poisoning incidents in Japan and 

Taiwan, respectively, where the cooking of 

rice oil contaminated with PCBs resulted in 

the production of PCDFs. The combined 

presence of PCBs and PCDFs in the cooked 

food caused chloracne and other toxic effects 

in the adults, and fetal mortality and developmental defects in their offspring (Rogan et al., 

1988; Hsu et al., 1994). 

❊ Like polychlorinated dioxins and furans, PCBs 

can be produced in small amounts during 

incineration processes and are therefore included in the unintentional byproduct category 

under the Stockholm Convention. 

Beyond the rice oil contamination poisonings, 

PCB toxicity has been demonstrated in wildlife 

and humans following environmental exposures. 

As detailed in the chapters to follow, PCBs have 

been associated with reproductive effects in 

wildlife populations in the Great Lakes (Chapter 

3) and far out in the North Pacific Ocean (Chapter 6). For humans, increased PCB concentrations in children from environmental exposures 

are associated with neurodevelopmental impacts 

(Fein et al., 1984; Jacobson and Jacobson, 

1996), findings supported by followup studies in 

the Great Lakes region (Lonky et al., 1996; 

Stewart et al., 2000) and in Dutch children 

(Patandin et al., 1999) (Chapter 4). 

Concern over the toxicity and persistence of 

PCBs in the environment led Congress in 1976 

to enact Section 6(e) of the Toxic Substances 

Control Act (TSCA). This includes prohibitions 

on the manufacture, processing, and distribution 

in commerce of PCBs. Under the Stockholm 

Convention there is a global ban on the manufacture of PCBs (UNEP 2000). Because of the 

magnitude of past use of PCBs and the continuing economic importance of previously manufactured PCB-containing equipment, countries must 

make determined efforts to identify, label, and 

remove PCB-containing equipment from use by 

2025. During this interval, the Stockholm Convention mandates a series of measures to reduce 

exposures and risk from further releases of PCBs 

to the environment, accompanied by prohibitions 

on reuse and export and import, except for the 

purpose of environmentally sound waste disposal. 

2-15 

Profiles of the POPs 

3. Byproduct POPs 

Polychlorinated dibenzo-p-dioxins (PCDD), 

polychlorinated dibenzofurans (PCDF) 

The term "dioxin" refers to a group of chemical 

compounds that share certain similar chemical 

structures and toxicological characteristics. 

Thirty toxic dioxin-like compounds exist and are 

members of three closely related families: 

PCDDs, PCDFs, and coplanar PCBs. The term 

dioxin is also used for the most well-studied and 

toxic of the dioxins, 2,3,7,8-tetrachlorodibenzop-dioxin (TCDD) (Table 2-12). PCDDs and 

PCDFs (Table 2-13) are not created intentionally, 

but can be produced inadvertently in nature and 

by a number of human activities. Combustion 

(Figure 2-8), elemental chlorine bleaching of pulp 

and paper (Figure 2-9), certain types of chemical 

manufacturing and processing, and other industrial processes all can create small quantities of 

dioxins. PCBs are no longer manufactured in the 

United States, but formerly were widely used in 

electrical equipment as coolants and lubricants. 

PCBs can also be formed in a similar manner to 

dioxins as byproducts of combustion processes 

(see previously). 

Dioxins have been central to a number of environmental controversies in recent decades. Dioxin 

(2,3,7,8-TCDD in particular) was a contaminant of 

the herbicide 2,4,5-trichlorophenoxyacetic acid 

(2,4,5-T) sprayed in Agent Orange defoliant during 

Figure 2-8. 

1973. 

Photo: U.S. EPA 

Stack emissions, New Orleans, Louisiana, 

the Vietnam War (Figure 2-10). Ensuing sprayer 

(Operation Ranch Hand personnel), soldier, and 

civilian exposures have resulted in ongoing inquiries, research, and veterans' health benefits compensation (IOM, 1994). In 1976, an explosion at 

a trichlorophenol herbicide production plant in 

Seveso, Italy, led to widespread environmental 

contamination, local livestock and wildlife mortality, 

very high human exposures and clinical illness 

(e.g., chloracne, a severe and prolonged acneform condition) (Figure 2-11), and evacuation of 

the surrounding region (Bertazzi et al., 1998). 

Residential dioxin exposure and evacuation also 

occurred at Times Beach, Missouri, following the 

spraying of dioxin contaminated waste oil for 

dust control in the early 1970s (Webb et al., 

1984). In occupational studies, cancer mortality 

increases have been reported in several groups of 

workers exposed to dioxin during herbicide production (Steenland et al., 2001; Ott and Zober, 

1996; Becher et al., 1998). The US EPA is 

currently assessing the impacts of dioxin on the 

general public in its draft document "Exposure 

and Human Health Reassessment of 2,3,7,8-

Tetrachlorodibenzo-p-Dioxin (TCDD) and Related 

Compounds" (www.epa.gov/ncea/dioxin.htm). 

Dioxins have the potential to produce an array of 

adverse effects in wildlife and humans. Dioxins 

can alter the growth and development of cells in 

ways that can lead to many kinds of impacts. 

These include adverse effects upon reproduction 

and development, suppression of the immune 

system, chloracne, and cancer. Although data on 

risks to children are limited, fetuses, infants, and 

children may be more sensitive to dioxin exposure because they are exposed during critical 

windows of development and during rapid 

growth. 

Dioxins are believed to exert these toxic effects 

in similar ways; that is, they share a common 

mode of toxicity. As a result, scientists use an 

approach that adds together the toxicity of individual dioxins in order to evaluate complex environmental mixtures to which people are exposed. Because dioxins differ in their toxic 

potential, the contribution of each component in 

2-16 

Profiles of the POPs 

Figure 2-9. fluent, a source of polychlorinated dioxins and furans, Columbia River, 1970s. 

Photo: U.S. EPA 

Figure 2-10. 

nated with dioxin, in Vietnam. 

Photo: USAF 

Pulp mill ef 

Aircraft spraying Agent Orange, contamithe mixture must be accounted for in estimating 

the overall toxicity. To do so, international 

teams of scientists have developed toxicity 

equivalence factors (TEFs) that compare the 

toxicity of different dioxins to the most toxic 

congener, 2,3,7,8-TCDD. Given these factors, 

the toxicity of a mixture can be expressed in 

terms of its toxicity equivalents (TEQ), which is 

the amount of 2,3,7,8-TCDD exposure it would 

take to equal the combined toxic effect of all the 

dioxins found in that mixture. 

Most dioxin enters ecological food webs by being 

deposited from the atmosphere, either directly 

following air emissions or indirectly by processes 

that return dioxins already present in the environment to the atmosphere. Once they reach the 

environment, dioxins are highly persistent and 

Figure 2-11. Chloracne caused by high exposure to dioxin. 

Photo: A. Geusau (Geusau et al., 2001/EHP) 

2-17 

Profiles of the POPs 

can accumulate in the tissues of animals. Most 

dioxin exposure occurs through the diet, with 

more than 95% of dioxin intake for a typical 

person coming through dietary intake of animal 

fats. Fortunately, dioxin levels in the environment have declined significantly since the 1970s, 

following EPA regulatory controls and industry 

actions. EPA’s best estimates of emissions from 

sources that can be reasonably quantified indicate that dioxin emissions in the United States 

decreased by about 75% between 1987 and 

1995, primarily through reductions in air emissions from municipal and medical waste incinerators. Substantial further declines continue to be 

documented. 

References 

Agency for Toxic Substances and Disease Registry 

(ATSDR). 1993a. Toxicological profile for aldrin/ 

dieldrin. U.S. Department of Health and Human Services. 

ATSDR. 1993b. Toxicological profile for heptachlor/ 

heptachlor epoxide. U.S. Department of Health and 

Human Services. 

ATSDR. 1994. Toxicological profile for 

chlorodibenzofurans. U.S. Department of Health and 

Human Services. 

ATSDR. 1996a. Toxicological profile for endrin and 

endrin aldehyde. U.S. Department of Health and Human Services. 

ATSDR. 1996b. Toxicological profile for toxaphene. 

U.S. Department of Health and Human Services. 

ATSDR. 1996c. Toxicological profile for 

hexachlorobenzene. U.S. Department of Health and 

Human Services. 

ATSDR. 1997. Toxicological profile for polychlorinated 

biphenyls (update). U.S. Department of Health and 

Human Services. 

ATSDR. 1998. Toxicological profile for chlorinated 

dibenzo-p-dioxins (update). U.S. Department of Health 

and Human Services. 

ATSDR. 2000. Draft toxicological profile for DDT/ 

DDD/DDE (update). U.S. Department of Health and 

Human Services. 

Arctic Monitoring and Assessment Program (AMAP). 

1998. AMAP Assessment Report: Arctic Pollution 

Issues. Oslo, Norway. 

AMAP. 2000. PCB in the Russian Federation: Inventory and proposals for priority remedial actions. Oslo, 

Norway. AMAP Report 2000:3. 

Bailey RE. 2001. Global hexachlorobenzene emissions. 

Chemosphere 43:167-182. 

Becher H, Steindorf K, Flesch-Janys D. 1998. Quantitative cancer risk assessment for dioxins using an occupational cohort. Environ Health Perspect 106 (suppl 

2):663-670. 

Bertazzi PA, Bernucci I, Brambilla G, Consonni D, 

Pesatori AC. 1998. The Seveso studies on early and 

long-term effects of dioxin exposure: review. Environ 

Health Perspect 106(suppl. 2):625-633. 

Beyer WN, Heinz GH, Redmon-Norwood AW, eds. 

1996. Environmental Contaminants in Wildlife: Interpreting Tissue Concentrations. Clemson, SC: SETAC 

Special Publications, Clemson University. 

Brinkhuis RP. 2001. Toxicology information from US 

government agencies. Toxicol 157(1-2):25-49. 

Burton WB, Pollard GE. 1974. Rate of photochemical 

isomerization of endrin in sunlight. Bull Environ Contam 

Toxicol 12:113-116. 

Callahan MA, Slimak MW, Gabel NW, May IP, Fowler 

CF, et al. 1979. Water-related environmental fate of 

129 priority pollutants. U.S. EPA Office of Water Planning and Standards. Washington, DC. EPA/440/4-79-

029b. 

Chavasse DC, Yap HH, eds. 1997. Chemical Methods 

for the Control of Vectors and Pests of Public Health 

Importance. Document WHO/CTD/WHOPES/97.2. 

World Health Organization, Geneva, 129 pp. 

Cutright CR. 1954. A codling moth population resistant to DDT. J Econ Entomol 47:189-190. 

2-18 

Profiles of the POPs 

DeBach P, Rosen D. 1991. Biological Control by Natural Enemies. Cambridge, UK: Cambridge University 

Press. 

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2-21 

Profiles of the POPs 

Appendix. Selected Federal Sites for POPs Toxicity Information 


❊ U.S. Department of Health and Human Services, National Library of Medicine (NLM; 

www.nlm.nih.gov) 

–	 Medline/PubMed, covering medical literature; 

– Toxnet, toxicology data network; 

–	 HSDB, Hazardous Substances Data Bank, 

focusing on the toxicology of potentially 

hazardous chemicals, with information on 

human exposure, industrial hygiene, emergency handling procedures, environmental 

fate, regulatory requirements, and related 

data 

❊ U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry (ATSDR; www.atsdr.cdc.gov) 

– 	ToxFAQs, summaries of hazardous substance information; 

– 	Toxicological Profiles of hazardous substances (www.atsdr.cdc.gov/toxpro2.html) 

❊ U.S. Environmental Protection Agency (U.S. 

EPA; www.epa.gov) 

–	 IRIS, Integrated Risk Information System 

(IRIS), a database of human health effects 

that may result from exposure to various 

substances found in the environment 

(www.epa.gov/iris) 

–	 PBT, Persistent Bioaccumulative Toxic, 

home page, containing summaries of PBT 

chemicals, EPA action plans, and regulatory initiatives (www.epa.gov/pbt) 

–	 ECOTOX database system, providing 

chemical-specific toxicity values for aquatic 

life, terrestrial plants, and terrestrial wildlife 

(www.epa.gov/med/databases/ 

databases.html#aquire) 

❊ U.S. Department of the Interior, U.S. Geological Survey, Patuxent Wildlife Research 

Center (www.pwrc.nbs.gov/research/ecr/) 

–	 Contaminant Exposure and Effects Terrestrial Vertebrates Database 

– Contaminant Hazards Review On-Line 

For further information on toxicology data sources, see Toxicology, Volume 157, Issues 1-2, Pages 1–164, 

12 January 2001. For federal sources, see specifically Brinkhuis, 2001. Hard copies of many federal 

documents are available from performing agencies, the Government Printing Office, and/or the National 

Technical Information Service (NTIS Tel: 703-605-6000). 

2-22 

Introduction 

life. 


cause adverse effects. 


served. 


Persistent Organic Pollutant 

Residues and their Effects on Fish 

and Wildlife of the Great Lakes Chapter 3 

For nearly two centuries the Great Lakes of 

North America have been the receiving waters 

for industrial and municipal wastes. Their story 

is illustrative of persistent organic pollutant 

(POPs) impacts in many lakes, streams, and 

rivers across the United States. The contamination of the Great Lakes with persistent and 

bioaccumulative compounds, including those 

designated as POPs under the Stockholm Convention, has been studied in detail and demonstrated to cause population-level effects on wildThe large size of the lakes had led to the 

commonly held, yet mistaken, belief that it was 

impossible to contaminate them sufficiently to 

As human populations 

and industrialization of the Great Lakes basin 

increased, and the complexity and magnitude of 

the industries grew, it became apparent that it 

was indeed possible to contaminate the lakes to 

the extent that adverse effects would be obThe release of persistent and 

bioaccumulative compounds eventually resulted 

in thresholds for adverse effects being exceeded 

in a number of wildlife populations. 

observed adverse effects in some species. However, several of the POPs were responsible for 

most of the observed effects. These include the 

insecticides dieldrin and DDT, the industrial polychlorinated biphenyls (PCBs), and the byproducts 

of incineration and chemical production, polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Although 

these POPs may have had adverse impacts on a 

number of species, their effects have been best 

documented for a few sentinel species such as 

lake trout (Salvelinus namaycush) (Giesy and 

Snyder, 1998), bald eagles (Haliaeetus 

leucocephalus) (Bowerman et al., 1995, 1998), 

colonial fish-eating water birds such as the cormorant (Phalacrocorax auritus) and Caspian 

tern (Sterna caspia) (Giesy et al., 1994a,b), and 

the mink (Mustela vison) (Giesy et al., 1994c; 

Tillitt et al., 1996). 

The experiences in the Great Lakes have resulted in a greater understanding of the potential 

hazards of releasing persistent, bioaccumulative, 

toxic compounds into the environment. Many of 

the substances are no longer manufactured or 

their use is heavily restricted. Concentrations of 

the most problematic 

compounds such as 

DDT and PCBs have 

declined, but the current rates of decline 

are very slow, such that 

it will be a long time 

before the concentrations in both fish and 

birds of the Great 

Lakes environment 

reach “background” 

concentrations (Figures 

3-2 to 3-4) (Giesy and 

Figure 3-1. 

compounds in extract of Great Lakes fish. 

Photo: J.P. Giesy 

Chromatogram showing organochlorine 

Literally thousands of 

contaminants can now 

be found in the tissues 

of fish and wildlife of 

the Great Lakes (Figure 

3-1). Concentrations of 

all of the compounds 

designated for control 

under the Stockholm 

Convention have been 

found at elevated levels 

in Great Lakes wildlife, 

and all could have contributed to some of the 

3-1 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 


Figure 3-2. 

the four uppermost Great Lakes between 1972-1993. 

Redrawn from MDNR (2001). 

Concentrations of PCBs in lake trout from 

Snyder, 1998). The trends for PCBs and DDTs 

are similar to those for the other Stockholm 

Convention POPs in both fish and birds. These 

trends demonstrate several things. First, fish and 

wildlife became contaminated with POPs residues soon after they were introduced, reaching 

maximum concentrations in the early 1970s. 

Second, when use of these compounds was restricted in North America, concentrations began 

decreasing immediately, and within approximately 20 years had decreased to concentrations 

Figure 3-3. s in lake trout in 

the four uppermost Great Lakes. Redrawn from MDNR 

(2001). 

Concentrations of total DDT 

Figure 3-4. 

DDE in double-crested cormorant eggs collected from the 

Great Lakes (yellow squares = DDE; red triangles = 

PCBs). Data from Environment Canada, www.ec.gc.ca/ 

ind/English/Toxic/default.cfm 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

1970 1975 1980 1985 1990 1995 2000 

Year 

Concentration (mg/kg) 

Mean wet weight concentrations of PCBs and 

at or near the threshold for effects. Even though 

the manufacture of these compounds ceased 

over 25 years ago, they remain at significant 

concentrations in wildlife. This lingering effect 

occurs because concentrations of POPs, once 

introduced into the environment, take a long 

time to decrease to nondetectable concentrations. Third, current concentrations in biota are 

no longer decreasing at the same rate that they 

once were. This slower rate is caused, in part, 

by continued input to the lakes from reservoir 

sources and from long-range atmospheric transport (Giesy and Snyder, 1998; Simcik et al., 

1999). 

In this report, we provide examples of the concentrations of selected POPs in wildlife and the 

adverse effects that have been caused by exposure to these compounds in the Great Lakes. To 

do this, we perform a simple risk screening by 

comparing concentrations of the POPs in tissues 

or the diets of wildlife with the threshold concentration for adverse effects. This comparison is 

done by calculating hazard quotients (HQs) (Table 

3-1). The HQ is the ratio of the measured concentration divided by the threshold concentration 

for effects, using either tissue or dietary concentrations. For instance, the concentration of PCBs 

in fish in the diet of a fish-eating bird can be 

compared with the dietary No Observable Adverse Effect Level (or concentration) (NOAEL). 

3-2 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 

Table 3-1. d Quotients (HQs) 

HQ = Concentration in Fish 

NOAEL 

HQs were calculated for: 

Total PCBs 

TCDD-TEQ (calculated) 

Calculation of the HQ assumes animals eat only the 

fish species of interest. 

“worst-case” estimate. 

Calculation of Hazar 

This is a conservative or 

The NOAEL is the highest dose or concentration 

at which no adverse effects have been observed. 

Effects would be increasingly expected as doses 

or concentrations rise above the NOAEL value. 

A HQ value of 10 indicates that the dietary 

concentration of PCBs is 10-fold greater than the 

threshold for causing an adverse effect in the 

piscivorous birds. Said another way, the concentration of PCBs in that species of fish would 

need to decrease by a factor of 10 before it 

would not be expected to cause any adverse 

effects to the birds that ate it. A HQ below 1 

indicates that, to the best of our current knowledge, adverse effects would be unlikely to occur. 

Fish 

Fish from all of the Great Lakes contain measurable concentrations of POPs and many other 

contaminants (Giesy and Snyder, 1998). In general, fish from Lakes Ontario and Michigan tend 

to have the greatest concentrations of POPs. 

Fish from Lake Ontario contain the highest concentrations of the insecticides mirex, DDT, and 

dieldrin. The lowest concentrations of most 

persistent, synthetic, chlorinated hydrocarbons 

are observed in fish from Lake Superior. The 

relatively high concentrations of toxaphene found 

in fish from Lake Superior have been the subject 

of several investigations (Swackhamer et al., 

1998; Shanks et al., 1999; Glassmeyer et al., 

2000). Concentrations of POPs in fish tissues 

have decreased by a factor of approximately 25 

since maximum concentrations were reached in 

the lower Great Lakes in the mid-1970s. Although there are differences among species and 

locations, in general the trends for POPs are 

either decreasing or stable. 

There is considerable difference of opinion in the 

literature about the extent to which effects on 

Great Lakes fish should be attributed to and 

among chemical contaminants. The types of 

effects that have been reported in Great Lakes 

fish include changes in behavior, reduced reproductive success, thyroid enlargement and decreased thyroid hormone content, premature 

sexual maturation in males, loss of secondary 

sexual characteristics, lessened plasma gonadotropin and gonadal hormone content, lessened 

egg fertility, and greater than expected embryo 

mortality and deformities (Leatherland, 1993). 

There is strong evidence that the endocrine systems of salmonid fish such as lake trout and 

chinook salmon are impaired, but at this time it 

is not clear if these observed imbalances are the 

result of exposure to POPs. 

Populations of several fish species have changed 

drastically from historical population levels. 

Many factors have been implicated in these 

declines, such as fishing, habitat loss, changes in 

genetic strains, and effects of the sea lamprey, 

in addition to a likely role for POPs and other 

pollutants. Historically, the reproductive success 

of salmonid fish in the Great Lakes was much 

poorer than that of the same species raised on 

the Pacific coast of the United States (Giesy et 

al., 1986; Willford et al. 1991). These adverse 

effects were often attributed to toxic substances, 

but it was difficult to demonstrate a cause-effect 

linkage. Specifically, several fish species have 

exhibited reproductive deficits that could be 

caused by exposure to POPs, although isolating 

the causal agent(s) has proven problematic because the mixtures of chemicals to which the fish 

are exposed vary over time and location. 

Of the many contaminants measured in fish and 

their eggs, DDTs, PCBs, polychlorinated dibenzop-dioxins (PCDDs), and polychlorinated 

dibenzofurans (PCDFs) are most often implicated 

in adverse effects (Giesy and Snyder, 1998). 

3-3 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 


The highest concentrations of POPs observed in 

fish eggs were for PCBs (11 mg/kg) and DDT (7 

mg/kg). Based on these levels, it was initially 

hypothesized that DDT and PCBs were most 

likely responsible for the observed egg mortality 

and reproductive toxicity. However, although 

both DDT and PCBs could cause lethality of lake 

trout eggs and fry in laboratory studies, the concentrations required to cause 30%–50% mortality 

were as much as 25 times greater than the concentrations observed in the eggs at that time. 

Thus, although concentrations of DDT observed 

historically in Great Lakes salmonids were in the 

range of the thresholds for adverse effects, as 

determined in laboratory studies, it is unlikely 

that these concentrations were the major cause 

of adverse effects seen in the eggs of feral fish 

from the Great Lakes. Current evidence indicates that PCDD, PCDF, and some of the nonand mono-ortho-substituted PCBs are principally 

responsible for blue-sac syndrome (Figure 3-5) 

and impaired reproductive performance of 

salmonid species in the lower Great Lakes, especially for lake trout (Walker and Peterson 1991, 

1994a,b; Zabel et al., 1995; Giesy and Snyder, 

1998). 

tions of lake trout have continued to reproduce 

naturally in Lake Superior, and reproductive 

success is improving (Curtis, 1990). A number 

of studies have indicated that the lake trout 

population recoveries in Lakes Huron and Michigan are related to reduced toxic organic residues 

in the eggs (see Giesy and Snyder, 1998, for a 

comprehensive review). 

Between 1978 and 1981, annual rearing mortalities in lake trout fry as great as 97% were 

described for hatchery-reared fish (Mac et al., 

1985). Mortality in these studies could not be 

attributed to disease or nutrition, and was characterized by erratic swimming behaviors and loss 

of equilibrium prior to death (swim-up syndrome). Poor survival was significantly correlated 

with the source of eggs and sperm, more so than 

the quality of the water in which the eggs were 

reared (Mac et al., 1985). In addition, a number 

of the adult lake trout produced fry that developed “blue sac” syndrome. This syndrome presents itself as an edematous (swollen with excessive fluid) condition that results in fluid filling the 

yolk sac, leading to a bluish color (Figure 3-5). 

Lake Trout 

Lake trout in Lake 

Michigan have not 

been naturally reproducing successfully for 

some time. The lake 

trout populations in 

both Lakes Michigan 

and Huron are maintained by stocking 

programs because 

natural reproduction of 

the populations is not 

sufficient to sustain 

populations (Willford et 

al., 1981). Nevertheless, there has been 

evidence of natural 

reproduction in Lake 

Huron (Weber and 

Clark, 1984). Popula-


Figure 3-5. fects of dioxin-like chlorinated hydrocarbons 

on developing lake trout fry (Spitsbergen et al., 1991). 

Photo: J. Spitsbergen (labels added). With permission of Elsevier Science. 

Ef 

Studies during the early 

1980s by scientists at 

the U.S. Fish and Wildlife Service (FWS) research laboratory in Ann 

Arbor, Michigan, indicated that the most 

likely cause of poor 

reproductive success 

was toxic chemicals 

(Mac et al., 1985; 

Willford et al., 1981; 

Giesy and Snyder, 

1998). Their analyses 

identified 167 chlorinated hydrocarbons in 

fish, although many 

more have been identified since. FWS researchers considered it 

unlikely that a correlation could be established 


3-4 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 

between specific chemicals and effects because 

of the large number of compounds observed in 

fish. They believed contaminants must be involved for the following reasons: 

1. Mortality was restricted to lake trout from 

southern Lake Michigan, which was also the 

area where the lake trout contained the 

greatest concentrations of PCBs and DDT. 

The mortality rate of fry from Lake Superior 

was small and that lake had the lowest concentrations of PCBs and DDT. 

2. Mortality occurred during the swim-up stage 

of development, during which time fry were 

most sensitive to the toxic effects of chemicals. 

3. The syndrome reached a maximum effect in 

both lake trout and chinook salmon populations at the same time. 

Thus, it was thought that DDT and PCBs were 

most likely responsible for the observed toxicity. 

However, no blue-sac disease, the syndrome 

observed in the fry hatched from eggs of feral 

females, was observed in laboratory studies of 

the effects of DDT or PCBs. This finding suggested that the complex mixture of contaminants 

in fish, and the cause of blue-sac disease, had 

not been completely identified or quantified. 

Further studies on lake trout in the lower Great 

Lakes demonstrated the link between blue-sac 

disease/impaired reproductive performance and 

the levels of PCDD, PCDF, and some of the nonand mono-ortho-substituted PCBs measured as 

dioxin toxicity equivalents (TEQs) (Walker et al., 

1991; Walker and Peterson, 1991, 1994a,b; 

Cook et al., 1997; US EPA 2001). The threshold for toxic effects of TEQ on lake trout sac fry 

is approximately 30-40 ng/kg and the lethal 

dose for 50% mortality (LD50) is approximately 

47–70 ng/kg wet weight body burden (Figure 3-

6) (Walker et al. 1991; Walker and Peterson, 

1994a,b). Toxicity is manifest from 1 week 

prior to hatching through the sac-fry stage of 

development (Spitsbergen et al., 1991). Lake 

trout are among the most sensitive species to 

dioxin toxicity. Thus, they can be used as sentinels for other species. Current concentrations of 

2,3,7,8-tetrachlorodibenzo-p-dioxin TEQs remain 

near the threshold for mortality in lake trout fry 

(Walker and Peterson, 1994a). By 1988, concentrations of TEQs had decreased to 8 and 29 

ppt in Lakes Michigan and Ontario, respectively. 

These concentrations are less than the threshold 

of approximately 40 ppt, but only slightly in the 

case of Lake Ontario (see Giesy and Snyder, 

1998, for further details). 

No measurements of historical concentrations of 

TEQs in fish tissue are available. However, the 

use of sediment TEQ concentrations from a 

dated sediment core to infer historical concentrations in lake trout indicate that, historically, the 

threshold concentration would have been exceeded (Cook and Burkhard, 1998). Furthermore, until recently lake trout hatched from 

females collected from the Great Lakes suffered 

a relatively high incidence of blue-sac disease. 

Although it has been reported that this incidence 

can be caused by bacterial infections (Symula et 

al., 1990), the edematous condition seen is 

characteristic of exposure of lake trout to 

2,3,7,8-TCDD or structurally similar compounds 

(Walker and Peterson, 1994a; Cook et al., 

1997). Because the dose-response relationship 

for the dioxin-like compounds in lake trout is so 

steep, it is likely that the concentrations of dioxin TEQ in the eggs were well above the toxicity threshold for blue-sac syndrome (Guiney et 

Figure 3-6. 50 concentrations for effects of TEQs on 

lake trout (redrawn with permission from Walker and 

Peterson, 1994a). 

LD 

3-5 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 


al., 1996) in the recent past. Problematic levels 

are still reported, where extracts of whole adult 

lake trout from Lake Michigan continue to lead to 

lethality when injected into rainbow trout eggs in 

graded doses (Wright and Tillitt, 1996). The extract, which contained PCDD, PCDF, and PCB 

congeners, caused yolk-sac edema, cardiofacial 

deformities, and hemorrhage. All of these symptoms have been observed in Great Lakes fish and 

can be caused by exposure of fish eggs to TCDD. 

In summary, it is not possible to determine the 

actual degree to which POPs have affected lake 

trout populations in the Great Lakes (Zint et al., 

1995). It is likely that dioxin TEQs, primarily 

from dioxin-like PCB congeners, have caused 

reproductive impairment of lake trout in the 

lower lakes, but not Lake Superior. Declines in 

lake trout populations began in Lakes Ontario, 

Huron, and Michigan before concentrations of 

POPs were high enough to drastically reduce 

reproduction. This observation, along with the 

fact that “catch per unit effort” generally declines 

after populations have declined, indicates that 

initially non-contaminant effects were most likely 

the cause of the population declines of lake 

trout. Also, because populations began to decline before sea lamprey numbers were sufficiently high to cause severe population reductions, the most likely cause of the decline in lake 

trout populations in the lower lakes was overexploitation by the commercial fishery. POPs 

may have played a significant role in delaying 

reestablishment of lake trout in the lower lakes, 

but the effects should begin to abate now that 

concentrations of these compounds have declined 

to near the threshold for mortality of eggs and 

fry. 

Birds 

During the 1960s and 1970s, when the pesticide 

DDT was being used in the North American 

environment, populations of several sensitive bird 

species declined as individuals became unable to 

successfully incubate eggs because of abnormally 

thin shells (Cooke, 1973). The eggshell-thinning 

effect of DDT and its potent, stable, metabolite 

p,p’-DDE in sensitive species is well known, even 

to the lay public. Indeed, the contributions of 

DDT to population declines in bird species such 

as brown pelicans (Pelecanus occidentalis), 

peregrine falcons (Falco peregrinis), and bald 

eagles are probably the most famous incidents in 

wildlife ecotoxicology. Although many populations worldwide were adversely affected, some of 

the more notable species that suffered catastrophic declines in the Great Lakes basin 

included the osprey (Pandion halieatus), bald 

eagle, and many colonial fish-eating birds such as 

herring gulls (Figure 3-7), common and Caspian 

terns, and double-crested cormorants (Figure 3-

8). In fact, some of these species were almost 

completely extirpated from the Great Lakes 

basin. These effects, including declines in popuFigure 3-7. Herring gull colony in Lake Michigan. 

Photo: John P. Giesy 

Figure 3-8. Double-crested cormorant colony, Lake Huron. 

Photo: John P. Giesy 

3-6 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 

lations, have been best documented for colonial, 

fish-eating water birds (Gilbertson et al. 1991; 

Peakall and Fox, 1987). Although effects were 

not restricted to the Great Lakes basin, a number of species in the Great Lakes experienced 

significant population declines (Bowerman et al., 

1995, 1998). Many of these species, such as 

the double-crested cormorant, have experienced 

dramatic population increases since DDT was 

deregistered in the United States and environmental concentrations have declined (Ludwig, 

1984; Weseloh and Ewins, 1994). 

Bald Eagles 

There is no question that bald eagle (Figures 3-9, 

3-10) populations declined greatly from historical 

levels, but the specific reasons for these declines 

Figure 3-9. Bald eagle egg in eagle nest with habitat in 

background. 

Photo: D. Best/U.S. FWS 

Figure 3-10. Bald eagle in flight. 

Photo: U.S. FWS 

are less clear (Bowerman et al., 1995). The 

numbers of bald eagles in North America declined greatly after World War II (Grier, 1982; 

Postupalski, 1985). This decline was particularly 

acute in the Great Lakes region (Colborn, 1991). 

Habitat changes and killing of adults certainly 

played a role in the population dynamics of bald 

eagles in the continental United States and Great 

Lakes basin. However, the greatest effect on 

bald eagle populations was from DDT residues, 

specifically the degradation product p,p’-DDE, 

which is known to cause eggshell thinning in 

eagles (Peakall et al., 1973; Feyk and Giesy, 

1998). The effect of DDT residues on bald 

eagle reproductive success, like many other raptors, is inversely proportional to the dose of p,p’-

DDE (Figure 3-11). It is clear that this compound exceeded concentrations sufficient to 

cause population-level declines in bald eagles of 

the Great Lakes basin (Wiemeyer et al., 1984, 

1993; Bowerman et al., 1995). Beyond this, it 

is impossible to separate the potential effects of 

other organochlorine compounds, such as dieldrin, PCBs, and dioxins, all of which accumulated 

in eagles to concentrations that may have contributed to population-level declines (Wiemeyer 

et al., 1984, 1993; Giesy et al., 1995; 

Bowerman et al., 1998). 

In 1976, just after the use of DDT was cancelled 

in North America, there were approximately 30 

breeding pairs of eagles along the shores of the 

Great Lakes and 80 and 100 pairs in the interior 

regions of Michigan and Minnesota, respectively 

3-7 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 


Figure 3-11. 

the geometric mean p,p’-DDE concentration (ng/g wet 

weight) in the plasma of nestling bald eagles between 

1977–93 (Bowerman et al., 1995). 

Productivity of bald eagles as a function of 

(Figure 3-12). On ceasing the use of DDT in 

North America, concentrations of p,p’-DDE in 

the environment, particularly in the diets of fisheating birds, began to decline. Subsequently, 

once the concentrations had declined below the 

threshold for population-level effects, populations 

of eagles began to increase (Grier, 1982; 

Postupalsky, 1985). The number of breeding 

pairs has increased steadily since 1976 

(Postupalsky, 1985). 

Currently, bald eagles nesting along the shoreline 

of the Great Lakes do not reproduce as well 

as those nesting on inland bodies of water 

(Bowerman et al., 1995). Two common 

Figure 3-12. 

along the Great Lakes shorelines and in the interiors of 

Michigan and Minnesota for the period 1977 to 1993 

(Bowerman et al., 1995). 

Numbers of breeding pairs of bald eagles 

measures of the reproductive success of bald 

eagles are the number of young fledged per 

occupied nest, referred to as productivity (compared over the total number of nests in a specified region or area), and the reproductive success 

of each nest (given as the number of young produced in a specific nest, e.g., 0, 1, 2 chicks). 

Maintenance of a stable bald eagle population 

requires a productivity of approximately 0.7 

chicks/occupied nest/year. A healthy population, capable of exporting excess productivity to 

colonize other areas, is characterized by a productivity of greater than 1.0. Productivities less 

than 0.7 are insufficient to replace the loss of 

adults (Bowerman et al., 1995). The average 

productivity for bald eagles nesting along the 

shorelines of the Great Lakes is 0.7, which is just 

sufficient to maintain a stable population, but 

not to expand. Any expansion of bald eagle 

populations along the shoreline of the Great 

Lakes is due to immigration from other more 

productive areas. The productivities for the 

Michigan shoreline on Lakes Michigan and Huron 

are 0.53 and 0.25, respectively, which are insufficient to maintain stable populations, let alone 

support any expansion (Figure 3-13). Bald 

eagles along rivers with anadromous (fish that 

return to inland streams to breed) populations of 

Figure 3-13. 

Michigan. B.A. = Breeding area, the area bald eagles 

frequent when they are paired, breeding, and raising 

chicks, which may include several nests, only one of 

which is used per year (data from Bowerman et al., 

1998). 

Great Lakes 0.71 

47.3 

Measures of Productivity for Bald Eagle 

Breeding Areas in Michigan 

No. Fledged Yg./Occupied B.A. 

% Rate of Success of Occupied B.A. 

Statewide 

Inland 1.05 

64.9 

1.11 

68.8 

1.00 

62.7 

Anadromous 0.55 

39.4 

0.53 

35.6 

0.84 

55.0 

0.25 

18.8 

Michigan 

Reproductive success of bald eagles in 

3-8 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 

salmon from the Great Lakes have a very low 

productivity of 0.55. The reduced productivities 

along the shores of the Great Lakes and anadromous salmon streams may be due to a number 

of factors, including exposure to residual concentrations of p,p’-DDE, but may also be caused by 

exposure to PCBs, PCDDs, and PCDFs or other 

compounds (Giesy et al., 1994, Bowerman et 

al., 1995). In addition, there may be microclimatological effects in some areas and impacts of 

low food availability (Dykstra et al., 1998). Although it is impossible to know the exact contribution of each of the POPs to eagle reproductive 

impairment, it is likely that current concentrations of POPs such as PCBs (Figure 3-14) in the 

Great Lakes are sufficient to cause populationlevel effects on some subpopulations of bald 

eagles (Bowerman et al., 1995). 

Colonial Fish-Eating Birds 

Current concentrations of PCDD, PCDF, and 

PCBs in both Great Lakes piscivorous birds and 

their prey are less than they were in the 1960s 

and 1970s. Some bird populations, such as 

double-crested cormorants and herring gulls, have 

made dramatic recoveries since that time. 

Populations of other species, such as common 

and Forster’s terns, continue to decline. The 

concentrations of TEQ in several species appear 

to be greater than the threshold for discernible, 

population-level effects at several locations 

Total PCB Concentrations (ppb-wet wt.) 

in Bald Eaglet Blood Sera, 1987-88 

Great Lakes x = 185.6 ppb 

Inland x = 29.0 ppb 

Great Lakes x = 185.6 ppb 

Inland x = 29.0 ppb 

118 

246 

112 

520 

358 

114 33 

220 319 79 

54 

96 

135 

79 

30 

14 15 

18 

24 

33 

21 

27 

12 

29 

18 

21 

30 38 

40 

16 51 32 

61 

61 

32 23 

24 

11 

30 

8 

12 6 

13 

15 24 

Figure 3-14. 

bald eagles in Michigan (data from Bowerman et al., 

1991). 

Michigan 

Concentrations of PCBs in blood plasma of 

around the Great Lakes (see Giesy et al., 1994b, 

for a comprehensive review). For instance, subpopulations of double-crested cormorants and 

Caspian terns in Saginaw Bay and Green Bay 

continue to display embryo lethality (Figures 

3-15 and 3-16) and abnormally high rates of 

developmental deformities (Figures 3-17 and 

3-18). In general, all of the populations of fisheating birds from the Great Lakes are displaying 

symptoms of exposure to chlorinated chemicals 

at the biochemical level. 

PCDDs, PCDFs, and certain structurally similar 

PCBs have been demonstrated to cause a syndrome referred to as Great Lakes Embryo Mortality Edema and Deformities Syndrome 

(GLEMEDS) (Table 3-2). This syndrome, which 

Figure 3-15. Cormorant eggs. One died while hatching. 

Photo: John P. Giesy 

Figure 3-16. Correlation between embryo lethality (egg 

death) as a function of total dioxin toxicity equivalents in 

double-crested cormorant eggs from the Great Lakes 

(Giesy et al., 1994a; Tillitt et al., 1992). 

3-9 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 


Figure 3-17. Cormorant with cross-bill malformation. 

Photo: John P. Giesy 

is similar to chick edema disease, results in embryo lethality and developmental deformities in 

fish-eating birds. Although the degree of expression of GLEMEDS has decreased as concentrations of PCDDs, PCDFs, and PCBs have declined, certain species in some locations are still 

affected. These exposures are still causing lethality and deformities in embryos of all of the 

populations examined by research groups from 

the United States and Canada, including those 

from Michigan State University (extensively reviewed in Giesy et al., 1994a,b). The observed 

effects are greater than those observed in less 

contaminated populations not breeding on the 

Great Lakes, although these effects are translated into biologically significant population-level 

Figure 3-18. Rates of deformities per thousand doublecrested cormorant embryos for the Great Lakes (Giesy et 

al., 1994a). LS–Lake Superior, LM–Lake Michigan, LH– 

Lake Huron, GB–Green Bay 

Table 3-2. 

z Embryo lethality 

z Liver mixed function oxidase (MFO) induction 

z Unabsorbed yolk sacs 

z Vitamin A depletion 

z Porphyria 

z Teratogenesis 

Source: Gilbertson et al. (1991). 

Clinical signs of GLEMEDS 

effects only in the more contaminated areas, 

such as Saginaw and Green Bays. 

As with fish, the results of laboratory and field 

studies indicate that the lethality and deformities 

(Table 3-3) of embryos of fish-eating birds from 

the Great Lakes are caused by the toxic effects 

of multiple compounds expressed through the Ah 

receptor. The use of TEQ as the measurement 

unit also explains the observed effects better 

than single measurements of individual compounds (Geisy et al., 1994a). When the current 

concentrations of PCBs and PCB-derived TEQs 

in the diets of fish-eating birds of the Great 

Lakes were compared with NOAEL values for 

these species, based on both laboratory and field 

studies with these species as well as surrogates, 

the hazard quotients and exceedence values were 

greater than 1.0 for all of the species in all of the 

lakes (Giesy et al., 1994b; 1995). The magnitude of the hazard quotient values varies among 

species and lakes. Bald eagles are the most 

exposed and the most sensitive, whereas cormorants are relatively tolerant of the effects of PCBderived TEQs. 

Mammals 

In addition to colonial, fish-eating water birds, 

several other wildlife populations have been 

Table 3-3. mities caused by 

exposure to TEQs 

z Gastroschisis z Hemorrhaging 

z Crossed bills z Abnormal feathering 

z Clubfoot z Abnormal eyes 

z Dwarfed appendages z Hydrocephaly 

z Edema/ascites z Anencephaly 

Source: Giesy et al. (1994a). 

Defor 

3-10 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 

reported to be affected by contaminants in Great 

Lakes fish. Populations of mustelids, including 

mink (Mustela vison) (Figure 3-19) and river 

otter (Lutra canadensis), have declined in regions along the Great Lakes or along rivers that 

are not blocked by dams, to which fish from the 

Great Lakes have access (Giesy et al., 1994c). 

It is difficult to conduct a risk assessment for 

mink because accurate information on their diets 

is limited. A number of researchers have reported that feeding fish from the Great Lakes 

has resulted in adverse effects on ranch mink, 

and several analyses have been conducted to 

examine the effects of contaminant compounds 

(Giesy et al., 1994c; Kannan et al., 2000). In 

studies feeding Great Lakes fish, mink are simultaneously exposed to a number of synthetic, 

halogenated compounds, including POPs insecticides. Because the concentrations of many of 

these compounds are intercorrelated, it is difficult to separate their effects and determine 

which are most likely to have caused adverse 

effects in populations of wild or ranch mink. As 

little as 1% Great Lakes fish in the diet of mink 

is sufficient to cause adverse effects on survival 

and growth of the kits (Restum et al., 1998; 

Giesy et al., 1994c); 40% Great Lakes fish in 

the diet causes mortality of adult female mink 

(Heaton et al., 1995a,b). When adult female 

mink were fed 10% Great Lakes fish, the number of surviving kits was significantly reduced 

(Figure 3-20). Historically, when the concentrations of insecticides such as DDTs in the tissue of 

Figure 3-19. Mink in the wild eating fish. 

Photo: J. McDonald/Corbis.com 

Figure 3-20. Survival of mink kits as a function of varying 

proportions of Great Lakes fish in the maternal diet 

(Tillit et al., 1996; Heaton et al., 1995a). 

fish from the Great Lakes were higher, it was 

concluded that that they were unlikely to be the 

cause of the effects observed when fish from the 

Great Lakes were fed to ranch mink. The most 

likely causes of the observed effects are again 

the PCDDs, PCDFs, and PCBs. Although it is 

difficult to determine the exact cause of the 

observed effects, it is clear that residues present 

in fish from the Great Lakes can cause significant effects on the survival and reproduction of 

mink. 

Of all the pollutants to which mink have been 

exposed, PCBs seem to have had the greatest 

impact. Mink are one of the most sensitive 

species to the effects of PCBs. In an attempt to 

determine if current concentrations of PCBs 

represent a risk to mink, hazard quotients were 

calculated assuming that mink ate only Great 

Lakes fish in their diet (Heaton et al., 1995a,b). 

Hazard quotients for PCBs in fishes from the 

Great Lakes ranged from a minimum of 6.4 to a 

maximum of 83. Percent allowable consumption 

values for feeding Great Lakes fish to mink were 

all less than 100%, and ranged from as little as 

1.2% to as much as 19%, depending on the fish 

species and its source. Thus, there is no combination of Great Lakes fish that would result in a 

nonhazardous diet to mink. The average allowable fish content in the mink diet for all of the 

Great Lakes fish was 7.5% (Giesy et al., 1994c). 

The onset time and duration of exposure of mink 

to salmon is also problematic, such that mink 

3-11 
POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 


could be eating large quantities of salmon for 

several months during sensitive reproductive 

periods. The late fall and early winter is a critical period for exposure to toxicants, when mink 

are mating and the females are pregnant. During this period, several species of anadromous 

salmonid fish migrate into Michigan rivers to 

spawn. The coho and chinook salmon die soon 

after spawning and are deposited on the shores 

of the river. With the onset of cold weather, the 

carcasses of the salmon can persist along the 

shore for a prolonged period of time. In this 

way, these fish could be a substantial source of 

contaminants to mink. For instance, using average concentrations of TEQs in fish from the 

Great Lakes, HQ values were all greater than 

1.0, indicating some degree of risk to mink 

(Table 3-4). Most of the TEQs were contributed 

by PCBs. 

From a time perspective, consuming chinook 

salmon for as little as 2 weeks could deliver the 

Table 3-4. Hazard quotients for consumption of TEQcontaining Great Lakes fishes by mink 

Common carp 47 

Chinook salmon 11 

Alewife 

Northern pike 30 

Calculated from information contained in Heaton et al. (1995a,b) 

and Tillitt et al. (1996), and unpublished data on concentrations of 

residues in fish tissue, J.P. Giesy. 

5.8 

annual dose to mink that would be expected to 

affect reproduction (Giesy et al., 1994c). 

Conclusions 

❊ All of the compounds listed in the Stockholm 

Convention on POPs have been identified in 

fish and wildlife of the North American Great 

Lakes, even though some of these compounds, such as toxaphene, were never used 

in significant quantities in the region. This 

finding indicates that the source of some 

POPs in the Great Lakes ecosystem is longrange atmospheric transport. 

❊ Concentrations of POPs in Great Lakes fish 

have decreased significantly, approximately 

25-fold, since the use of these compounds 

ceased within the Great Lakes basin. 

❊ Concentrations of the key POPs, such as p,p’-

DDE and PCBs, in Great Lakes wildlife are 

currently either not declining or declining only 

slowly. POPs declines in Great Lakes waters 

have also slowed, reflecting a complex interrelationship among loss to sediments, temperature-dependent fluxes to and from the 

atmosphere, and continuing inputs from urban 

and other sources, local and remote (Miller et 

al., 2001; Swackhamer et al., 1999; Simcik 

et al., 1999). Further input reductions of 

POPs and the continued recovery of wildlife 

populations depends, in part, on controlling 

long-range atmospheric transport of POPs 

from other parts of the world (US EPA, 2000). 

❊ Historically, several POPs accumulated to 

sufficient concentrations to cause adverse 

effects on fish and wildlife in the Great Lakes. 

❊ The degradation product of the organochlorine insecticide DDT, p,p’-DDE, which causes 

eggshell thinning in raptors such as peregrine 

falcons, ospreys, and bald eagles, resulted in 

decreases in populations of these species to 

the point where they were almost completely 

extirpated from the Great Lakes basin. 

❊ PCDDs, PCDFs, and certain structurally similar PCBs caused a syndrome referred to as 

GLEMEDS in colonial fish-eating water birds 

of the Great Lakes. This syndrome, which is 

similar to chick edema disease, results in 

embryo lethality and developmental deformities in birds. The degree of expression of 

GLEMEDS has decreased as concentrations of 

PCDDs, PCDFs, and PCBs have declined, but 

certain species in some locations are still 

affected. 

❊ Concentrations of POPs residues, primarily 

PCDD, PCDF, and PCBs, in fish are still sufficient to cause mortality in adult mink and 

3-12 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 

severely reduce reproduction at as little as 1% 

Great Lakes fish in the diet. 

❊ Historically, concentrations of dioxin-TEQs, 

primarily from PCBs, were sufficient to cause 

blue-sac syndrome in sensitive fish species 

such as lake trout, and probably contributed to 

their population declines and restricted recovery. Currently, concentrations have decreased 

to a point where the incidence of blue-sac 

syndrome is rare. 

❊ At present, bald eagles nesting along the 

shorelines of the Great Lakes and along 

anadromous, accessible rivers have diminished 

reproductive capacity compared with those 

living at inland sites. 

❊ Even though concentrations of many of the 

POPs have decreased in Great Lakes wildlife 

subsequent to restriction of their use in the 

Great Lakes basin, some species of wildlife in 

some locations continue to be affected. 

❊ Failure to control sources of POPs outside the 

Great Lakes basin will limit the ability of the 

Great Lakes wildlife to recover. 

❊ The Great Lakes experience demonstrates that 

it is possible to sufficiently contaminate environments with residues to cause adverse effects. 

The experience in the Great Lakes is also one 

of hope, because controls on the production 

and release of POPs can result in reduced 

environmental concentrations and wildlife 

recovery. 

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Saginaw Bay, Michigan: 2. Hematology and Liver Pathology. Arch Environ Contam Toxicol 29:411-417. 

Kannan K, Blankenship AL, Jones PD, Giesy JP. 2000. 

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Risk Assess 6:181-201. 

Leatherland JF. 1993. Field observations on reproductive and developmental dysfunction in introduced and 

native salmonids from the Great Lakes. J Great Lakes 

Res 19:737-751. 

Ludwig JP. 1984. Decline, resurgence and population 

dynamics of Michigan and Great Lakes double-crested 

cormorants. Jack-Pine Warbler 62:91-102. 

Mac MJ, Edsall CC, Seeyle JG. 1985. Survival of lake 

trout eggs and fry reared in water from the upper Great 

Lakes. J Great Lakes Res 11:520-529. 

MDNR. 2001. Michigan fish contaminant monitoring 

program. 2001 Annual Report. Michigan Department 

of Natural Resources. 

Miller SM, Green ML, Depinto JV, Hornbuckle KC. 

2001. Results of the Lake Michigan Mass Balance 

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Kinter WB. 1973. DDE-induced egg-shell thinning: 

structural and physiological effects in three species. 

Comp Gen Pharmacol 4:305-314. 

3-14 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 

Peakall DB, Fox GA. 1987. Toxicological investigations 

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Restum JC, Bursian SJ, Giesy JP, Render JA, Helferich 

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Shanks KE, McDonald JG, Hites RA. 1999. Are pulp 

and paper mills sources of toxaphene to Lake Superior 

and Northern Lake Michigan? J Great Lakes Res 25 

(2):383-394. 

Simcik MF, Basu I, Sweet CW, Hites RA. 1999. Temperature dependence and temporal trends of polychlorinated biphenyl congeners in the Great Lakes atmosphere. Environ Sci Technol 33:1991-1995. 

Spitsbergen JM, Walker MK, Olson JR, Peterson RE. 

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ncea/raf 

Walker MK, Spitsberger JM, Olson JR, Peterson RE. 

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Salvelinus namaycush. Can J Fish Aquat Sci 48:875-

883. 

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Walker MK, Peterson RE. 1994a. Aquatic toxicology of 

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Walker MK, Peterson RE. 1994b. Toxicity of 2,3,7,8-

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3-15 

POPs Residues and their Effects on Fish and Wildlife of the Great Lakes 


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3-16 

Introduction 

Animals often act as sentinels for human health 

(NRC, 1991). This is especially true for humans 

who, through cultural tradition or free choice, live 

closer to nature and have lives intimately linked to 

the subsistence food sources in their local region. 

In turn, these susceptible populations can act as 

sentinels to the mainstream U.S. population, for 

whom the complexity of modern society and diverse dietary sources diffuse connections and make 

causal linkages to health outcomes difficult to isolate. Thus, the early findings of persistent organic 

pollutant (POPs) exposures and adverse effects on 

wildlife reproduction, development, and survival in 

the Great Lakes and other water bodies stimulated 

research to determine if similar effects were occurring in human populations. In particular, efforts 

centered on the families of sport fishers and Native 

Americans known to consume large amounts of 

Great Lakes fish. This chapter summarizes this 

research, providing information on human exposures, epidemiological results, and regulatory considerations for human populations in the Great 

Lakes region. Although the discussion is centered 

on the Great Lakes, its message relates to all communities in the United States exposed to POPs 

pollution. 

The chapter is based on epidemiological information: the study of disease in human populations. 

Epidemiological research is a difficult endeavor, 

reflecting the complexity of the species under 

investigation. This complexity affects the multiple 

exposures and endpoints experienced by humans 

and the variations, patterns, and linkages in exposures, as well as the statistical methods necessary to 

tease these apart. Laboratory confirmation of lowlevel toxicological results in humans is not usually 

an option because of ethical considerations. As a 

result, when interpreting data consideration must 

Persistent Organic Pollutants 

in the Great Lakes: Human 

Health Considerations

Chapter 4 

be given to the inherent difficulties in analyzing 

potential effects from low-level exposures. 

instance, an adverse human health impact may be 

difficult to demonstrate because the number of 

people affected is small relative to the statistical 

power of the study to isolate this effect. 

the control group in a study may also be exposed, 

albeit to a lesser degree, leading to a situation 

where both exposed and control groups may be 

exhibiting adverse effects and there appears to be 

no difference between the two. 

exposure, a common difficulty, also tends to diffuse 

results and weaken findings of effects. 

From another perspective, there may be no adverse effects from a POPs exposure and yet statistiFor 

For POPs, 

Misclassification of 

Paper company waste disposal basin in 1970: A source of 

pollutants to the Great Lakes. 

Photo: Minnesota Sea Grant, March 1970 

4-1 

 POPs in the Great Lakes: Human Health Considerations 

cally significant differences are found between 

control and exposed groups. This can be the result 

of such simple factors as performing multiple tests, 

some of which will eventually appear “abnormal” 

by chance alone because of the common p < 0.05 

(1 in 20) statistical significance value. More difficult 

to isolate are the effects of confounding and bias, 

where the control and exposed groups become 

unbalanced through study design limitations. For 

instance, lifestyle differences between sport fishers 

in the Great Lakes and the general population need 

to be considered before assigning health outcomes 

solely to dietary differences in POPs intake. For a 

more detailed analysis of these epidemiological data 

and considerations, see De Rosa et al. (1999) and 

Johnson et al. (1998). 

Historical Background on POPs 

Exposure Studies in the Great Lakes 

The first human exposure study of POPs in the 

Great Lakes was the 1974 study of polychlorinated 

biphenyl (PCB) intake from sport fish consumption 

(Michigan Sports Fishermen Cohort; Humphrey, 

1976). Sport fish eaters were found to consume 

on average 14.5 kg (32 pounds) of fish per year, 

some eating as much as 119 kg (262 pounds) per 

year. During the 1970s, this average was approximately five times the national per capita fish consumption rate commonly used in risk estimates. 

Individuals who regularly ate 11 kg (24 lbs) per year 

or more of Great Lakes fish had higher (p < 0.001) 

serum levels of PCBs than individuals who seldom 

or never ate such fish. The study was repeated in 

Recreational fishers and the Great Lakes. 

Photo: ATSDR 

1982, again indicating that individuals in the upper 

range of fish consumption had serum PCB levels 

approximately four times greater than unexposed 

individuals. These studies identified a positive 

correlation between human intake of toxic pollutants and the consumption of Great Lakes fish 

(Humphrey, 1976, 1988a,b, 1989). 

A similar assessment of body burden levels of PCBs 

and DDE was undertaken in the Wisconsin Sports 

Fish-Consumers Cohort Study (Fiore et al., 1989; 

Sonzogni et al., 1991). Using new technology for 

analyzing toxic chemicals in human blood, the 

investigators were the first to determine PCBspecific congeners in Great Lakes sport anglers. 

They determined that the congeners most frequently identified in human sera were also the most 

abundant congeners in the tissues of a variety of 

Wisconsin fish (Maack and Sonzogni, 1988). Body 

burden levels of PCB congeners and DDE were 

significantly correlated with the number of sport 

fish meals consumed. 

Both of these early studies demonstrated that human populations can be exposed to POPs through 

consumption of fish. Multimedia analyses support 

this finding, showing that most human exposure to 

chlorinated organic compounds (80-90%) comes 

from the food pathway (Figure 4-1). A lesser 

amount (5-10%) comes from air, and very small 

amounts (less than 1%) come from water (Birmingham et al., 1989; Newhook, 1988). Recent data 

indicate that fish consumption appears to be a 

major pathway for exposure to POPs chemicals, 

especially for compounds such as PCBs and dioxins (Fitzgerald et al., 1996; Schaum et al., 1999). 

Identification of Critical Great 

Lakes Pollutants 

Cooperation between Canada and the United 

States on the Great Lakes is managed through the 

International Joint Commission (IJC), established 

under the 1909 Boundary Waters Treaty. Among 

the IJC’s mandates is the responsibility for protecting the lakes and river systems along the border for 

the benefit of citizens and future generations. In 

1985, the IJC identified 11 of the most persistent 

and widespread toxic substances as critical Great 

4-2 

POPs in the Great Lakes: Human Health Considerations 

compounds (~30,000) are produced or used in the 

Great Lakes basin, about 1,000 of which have 

been identified in the Great Lakes environment. 

ATSDR Great Lakes Human Health 

Effects Research Program 

In 1990, the U.S. Congress amended the Great 

Lakes Critical Programs Act to investigate human 

health concerns and pollutants in the Great Lakes. 

In response, the Agency for Toxic Substances and 

Disease Registry’s (ATSDR) Great Lakes Human 

Health Effects Research Program (GLHHERP) was 

initiated in 1992. This program is designed to 

characterize exposure to toxic chemicals from 

consumption of Great Lakes fish and to investigate 

the potential for short- and long-term adverse 

health effects. The research program focuses on 

the initial 11 critical Great Lakes pollutants identified by the IJC, as well as other chemicals of conFigure 4-1. The Great Lakes food web. Heavy metals and 

many synthetic chemicals are absorbed by organisms and 

biaccumulate, with concentrations reaching toxic levels if 

exposure is great enough. 

at each step of the food web (Hicks et al., 1996). 

The concentration is magnified 

Lakes pollutants: PCBs, DDT, dieldrin, toxaphene, 

mirex, methylmercury, benzo[a]pyrene (a member 

of a class of substances known as polycyclic aromatic hydrocarbons [PAHs]), hexachlorobenzene 

(HCB), polychlorinated dibenzo-p-dioxins and 

dibenzofurans, and alkylated lead (IJC, 1983). 

Eight of these pollutants are on the initial list for 

the Stockholm Convention, with the remaining 

four global POPs incorporated under subsequent 

Great Lakes binational agreements (http:// 

www.epa.gov/glnpo/bns). 

Forty-two geographic locations in the U.S. and 

Canadian Great Lakes basin have been identified 

by the IJC as “Areas of Concern” because of high 

concentrations of these toxic pollutants (National 

Health and Welfare Canada, 1991) (Figure 4-2). 

Of these 42 locations, 31 are located within the 

boundaries of the United States (Hicks, 1996). 

Beyond the substances and locations prioritized by 

the IJC, many more commercial and industrial 

Figure 4-2. IJC areas of concern in the Great Lakes Basin 

(Great Lakes Fishery Commission, 1993). (#19 Collingwood Harbor has been delisted as an area of concern.) 

4-3 

 POPs in the Great Lakes: Human Health Considerations 

cern in the Great Lakes basin. The program has 

identified several sensitive human health endpoints 

for study, including behavioral, reproductive, developmental, neurologic, endocrinologic, and immunologic measures. ATSDR’s Great Lakes research 

further identified several human populations that 

may be at particular risk because of higher exposures to Great Lakes pollutants via fish consumption (Table 4-1). Predisposition to toxic injury in 

these populations can be due to behavior (e.g., 

degree of contaminated fish consumption), nutritional status, physiology (e.g., developing fetuses), 

or other factors. These communities of concern 

include subsistence fish anglers, Native Americans, 

pregnant women, fetuses, nursing infants of mothers who consume contaminated Great Lakes sport 

fish, young children, the elderly, the urban poor, 

and those with compromised immune function. 

Contemporary data continue to support the 

association between the consumption of contaminated Great Lakes fish and elevated body burdens 

of POPs, summarized by the following findings 

(Table 4-2): 

❊ Communities of concern in the Great Lakes 

basin are still exposed to POPs, including 

PCBs, polychlorinated dibenzo-p-dioxins and 

furans, and chlorinated pesticides (e.g., DDT) 

(Hanrahan et al., 1999; Stewart et al., 1999; 

Schantz et al., 1999; Johnson et al., 1998; 

Anderson et al., 1998; Dellinger et al., 1996; 

Fitzgerald et al., 1996; Lonky et al., 1996; 

Schantz et al., 1996; and Humphrey et al., 

2000). 

Table 4-1. Human populations at increased risk 

❊ Native Americans 

❊ Sport anglers 

❊ Elderly 

❊ Pregnant women 

❊ Fetuses 

❊ Nursing infants 

❊ Women and men of reproductive age 

❊ Immunologically compromised persons 

❊ Levels of some contaminants in Great Lakes 

sport fish are above the advisory limits set by 

the state and federal governments (Dellinger 

et al., 1996). 

❊ Sport fish eaters consume on average two to 

three times more fish than the estimate of 6.5 

g/day for the general U.S. population 

(Courval et al., 1996, 1999; Fitzgerald et al., 

1996, 1999; Schantz et al.,1996, 1999; 

Anderson et al., 1998; Hanrahan et al., 

1999; He et al., 2001). In one survey in 

Michigan, Great Lakes sport fish consumers 

reported eating on average 42 g/day (Michigan Department of Environmental Quality, 

1996). The reported weight of fish consumed 

declined from the early 1970s to 1990s (He 

et al., 2001). 

❊ Consumption of Great Lakes fish appears to 

be the major pathway of exposure for some 

POPs (Fitzgerald et al., 1996, 1999; Stewart 

et al., 1999). Men eat more fish than do 

women, both genders eating Great Lakes fish 

during most of their reproductive years 

(Courval et al., 1996; Fitzgerald et al., 1996, 

1999; Lonky et al., 1996; Waller et al., 

1996; Hanrahan et al., 1999). 

❊ Body burden levels for some of the POPs are 

two to eight times higher than those of the 

general U.S. population (Anderson et al., 

1998; Hanrahan et al., 1999; Schantz et al., 

1996, 1999; He et al., 2001). A significant 

trend of increasing body burden is associated 

with increased fish consumption (Fitzgerald et 

al., 1996, 1999; Falk et al., 1999; Hanrahan 

et al., 1999). 

❊ Although background levels of PCBs appear 

to have declined in Great Lakes residents by 

the early 1990s, serum PCB levels among 

consumers of sport-caught Great Lakes fish 

did not significantly decrease (He et al., 

2001). 

Epidemiological Data 

Epidemiological studies of Great Lakes populations 

have centered principally on reproductive effects 

and neurobehavioral/cognitive impacts on children. 

4-4 

POPs in the Great Lakes: Human Health Considerations 

Table 4-2. Exposure studies in human populations 

PCBs and DDE levels were significantly higher 

in high fisheaters. High fisheaters presented 

On the basis of these and similar studies, the National Research Council (1999) concluded that: 

In humans, results of cognitive and 

neurobehavioral studies of mother-infant 

cohorts accidentally exposed to high concentrations of PCBs and PCDFs and of motherinfant cohorts eating contaminated fish and 

other food products containing mixtures of 

PCBs, dioxin, and pesticides (such as DDE, 

dieldrin, and lindane) provide evidence that 

prenatal exposure to these HAAs [hormonally 

active agents] can affect the developing nervous system. 

Many of the studies on which this conclusion is 

based originated from Great Lakes epidemiological 

research and are summarized below. 

Reproductive Effects 

In a cross-sectional mail survey of reproductive-age 

Michigan licensed anglers and their partners, 

Courval et al. (1999) reported a modest association 

4-5 

 POPs in the Great Lakes: Human Health Considerations 

in men between sport-caught fish consumption and 

the risk of conception failure after trying for at least 

12 months. The authors examined the association 

between exposure and effects by calculating odds 

ratios, the odds of illness among the exposed 

group divided by the odds of illness in an unexposed group. On the basis of answers to questionnaires, 15% of couples had reported conception 

failure. Among men, the unadjusted odds ratios 

(ORs) for conception failure were 1.2, 1.3, and 2.0 

across the three increasing levels of sport-caught 

fish consumption compared to no consumption 

(trend test p = 0.06). Adjusting for a number of 

variables that may affect study results, i.e., age, 

region of Michigan, smoking, and alcohol consumption, the ORs were 1.4, 1.8, and 2.8, respectively. For women, the unadjusted ORs for conception were 0.9, 1.0, and 1.4 with increasing fish 

consumption (trend test p = 0.35). When the 

same covariates and partner’s sport-caught fish 

consumption were included in the model for conception failure in women, the ORs became 0.8, 

0.8, and 1.0, respectively, indicating no increased 

risk from female exposure. 

A series of studies on reproductive health has been 

performed on a cohort of New York State anglers 

and their spouses. In this cohort, questionnaires 

provided data on each person’s species-specific fish 

consumption pattern, medical and reproductive 

histories, sociodemographic characteristics, and 

other lifestyle behaviors. Individual fish consumption at the time of enrollment in this study was 

characterized by self-reported duration and frequency, and used to calculate a PCB exposure 

index. Health outcomes were assessed through a 

combination of questionnaires and birth certificates. Multiple regression statistical analyses were 

carried out to control for identified variables. Findings from this cohort include the following: 

❊ Mendola et al. (1995) reported no significant 

relationship between estimated low-to-moderate PCB intake from Great Lakes fish (up to 7 

mg/lifetime) and the risk of clinically recognized spontaneous fetal death. 

❊ Mendola et al. (1997) identified significant 

menstrual cycle length reductions with consumption of more than one fish meal per 

month (1.11 days). Women who consumed 

contaminated fish for 7 or more years also 

had shorter cycles (–0.63 days). The results 

were consistent with measures of frequency of 

consumption and the index of lifetime PCB 

exposure having a stronger relationship with 

menstrual cycle length than the number of 

years of fish consumption. 

❊ Buck et al. (1997) reported no adverse association between the duration of consumption 

of contaminated fish from Lake Ontario and 

time-to-pregnancy. 

❊ Buck et al. (2000) reported that maternal, but 

not paternal, consumption of fish from Lake 

Ontario may reduce fecundability (ability to 

conceive) among couples attempting pregnancy. 

Neurodevelopmental Effects 

Of the epidemiological studies of POPs exposures, 

none is more central than the Lake Michigan Maternal/Infant Cohort Study (Fein et al. 1984; 

Jacobson et al. 1985, 1990a,b). This study reported both developmental disorders and cognitive 

deficits in the offspring of mothers who were exposed to PCBs via fish consumption for at least 6 

years before and during pregnancy. Developmental effects included a statistically significant decrease 

in gestational age (by 4.9 days), birth weight (by 

160 to 190 g), and head circumference (by 0.6 

cm). Decreased weight and neurological effects 

were still evident compared with the control population at 5 and 7 months post-term (Jacobson 

and Jacobson, 1988; Jacobson et al., 1985). 

Neurobehavioral deficits observed in babies included greater inclination to startle; poorer motor 

reflex and neuromuscular function; depressed responsiveness, as evidenced by a greater number of 

hypoactive reflexes; impaired visual recognition; 

and poor short-term memory at 7 months of age. 

At 4 years following birth, these deficits were still 

evident in weight gain, depressed responsiveness, 

and reduced performance on the visual recognition-memory test, one of the best validated tests for 

the assessment of human cognitive function 

(Jacobson et al., 1990a,b). 

4-6 

POPs in the Great Lakes: Human Health Considerations 

Although these data provide substantial evidence of 

in utero effects from PCBs, some significant questions were raised regarding causality because of 

recognized limitations in the studies. These included loss of study participants over time, a nonrandom sampling technique for the selection of the 

study population, limited statistical power because 

of the size of the control group, and analysis only 

of total PCBs. Also, the standards used (Aroclor 

1016 and 1260) as references to quantify total 

PCBs accounted for only a small portion of the 

PCB congeners detected (Swain, 1991). Therefore, the analytical methods used to measure PCB 

levels may not have been appropriate. Moreover, 

many potential confounding variables have been 

identified, including exposure to other chemical 

contaminants and the mothers’ health status at the 

time of the study. Nev­

❊ Were twice as likely to be at least 2 years 

behind in reading comprehension 

❊ Had poorer short- and long-term memory 

❊ Had difficulty paying attention. 

The authors concluded that these intellectual impairments were attributable to in utero exposure to 

PCBs, and that concentrations of PCBs in maternal serum and milk at delivery were slightly higher 

than in the general U.S. population. 

The initial findings of the Lake Michigan Maternal/ 

Infant Cohort Study have now been replicated in 

independent cohort analyses. Similar results were 

seen in the Oswego Newborn and Infant study, a 

prospective longitudinal cohort study examining 

behavioral effects in 

ertheless, a subsequent 

Neurobehavioral testing of a child. 

Photo: ATSDR 

newborns, infants, and 

retrospective analysis by children exposed preSwain (1991) found that and postnatally to envithe relationship between ronmental toxicants. 

PCB exposure and Lonky et al. (1996) found 

transplacental passage that maternal exposure 

was strongly affirmed, to Lake Ontario fish 

and the relationship contaminants (e.g., 

between PCB exposure PCBs) was associated 

and developmental with neurobehavioral 

effects and cognitive deficits when assessed 

deficits was affirmed shortly after birth. A 

with reasonable cer- total of 559 newborns of 

tainty. women who had high 

exposure, low exposure, 

In a followup examina- or no exposure to Lake 

tion of 212 children from the Lake Michigan Ma- Ontario fish were examined using the Neonatal 

ternal/Infant Cohort Study, the Behavioral Assessment Scale (NBAS) 12-24 hours 


neurodevelopmental deficits assessed in infancy after birth and again at 25-48 hours after birth. 


and early childhood were found to persist at age 11 Newborns of high-fish-consuming mothers exhib­


(Jacobson and Jacobson, 1996). The study results ited the following deficits: 


indicated that the most highly exposed children, 


those with prenatal exposures equivalent to at least ❊ A greater number of abnormal reflexes 


1.25 μg/g in maternal milk, 4.7 ng/mL in cord (p < 0.001) 


blood, or 9.7 ng/mL in maternal serum ❊ Less mature autonomic responses (p < 0.001) 


❊ Were three times as likely to have low average ❊ Less attention to visual and auditory stimuli in 


IQ scores (p < 0.001) 	 comparison to newborns of low- or no-fishconsuming mothers (p < 0.01) 

4-7 

 POPs in the Great Lakes: Human Health Considerations 

These results indicate that newborns of mothers 

who consumed 2.3 salmon or trout meals per 

month scored more poorly on the NBAS than 

newborns from the low-exposure or control 

groups. These results represented the first replication and extension of the neonatal results of the 

Lake Michigan Maternal/Infant Cohort study by 

Jacobson et al. (1984). 

Further analysis of the Oswego data on newborns 

revealed significant relationships between cord 

blood concentrations of the most highly chlorinated 

PCBs and performance impairment on the NBAS 

habituation and autonomic tests. No significant 

relationship was found between PCBs of lesser 

chlorination, DDE, hexachlorobenzene, mirex, 

lead, or mercury on any NBAS performance test 

(Stewart et al., 2000). The relationship between 

prenatal exposure to PCBs and performance on 

the Fagan Test of Infant Intelligence (FTII) was also 

assessed in the Oswego infants at 6 months and 

again at 12 months of age. The results indicated a 

significant relationship between exposure to PCBs 

and poor performance on the FTII. No significant 

relationship was found between exposure to DDE 

or methylmercury on any tests of the FTII (Darvill 

et al., 2000). 

Studies of the impact of POPs, particularly PCBs, 

on human neurobehavioral development are not 

limited to the Great Lakes region of the United 

States and have been performed in other regions 

of the United States and abroad. In the early 

1980s, the North Carolina Breast Milk and Formula Project was conducted with more than 800 

mother-infant pairs who were exposed to background levels of PCBs (Rogan and Gladen, 1985; 

Rogan et al., 1986; Rogan and Gladen, 1991). 

When the North Carolina children were tested after 

birth, children of mothers with higher PCB concentrations in their breast milk exhibited the same 

behavioral deficits that were characteristic of the 

children studied in the Lake Michigan Maternal/ 

Infant Cohort and the newborns of the Oswego 

Newborn and Infant Study. However, at 3 years of 

age the behavioral deficits were no longer detectable in the children from the North Carolina study. 

In an occupational study of women exposed to 

PCBs during the manufacture of capacitors in New 

York State, decreased gestational age and depression of weight at birth were associated with PCB 

exposure (Taylor et al., 1989). 

Internationally, a series of studies in Europe are 

investigating the effects of exposure to PCBs and 

polychlorinated dioxins and furans on neurological 

development in the developing fetus and newborn 

(Huisman et al., 1995). These studies have linked 

high maternal levels of PCBs, PCDDs, and PCDFs 

with reduced neonatal neurological performance. 

The data also indicate that high in utero exposure 

to PCBs (measured in maternal serum) is associated 

with lower psychomotor scores at 3 months of age 

(Koopman-Esseboom et al., 1996) and with poorer 

cognitive functioning in preschool children at 42 

months of age (Patandin et al., 1999). In another 

European mother-infant cohort, PCBs in maternal 

milk were associated with decreased performance 

on the Bayley II mental development index at 7 

months, but not with other tests of neurotoxicity 

(e.g., FTII) or when using serum PCB concentration measures (Winneke et al., 1998). 

Neurobehavioral changes have also been demonstrated in monkey and rat offspring following low 

perinatal doses of dioxin (Schantz and Bowman, 

1989; Markowski et al., 2001) and PCBs (Rice, 

1999; Schantz et al., 1989; Levin et al., 1988). 

Other Cognitive and Systemic 

Health Effects 

Beyond the developmental neurobehavioral findings reported above, additional studies have been 

conducted on Great Lakes fish consumers across 

different age groups and different health endpoints. 

These include the following: 

❊ The effects of POPs on the immune system 

have been investigated in breast-fed infants 

whose mothers consumed contaminated Great 

Lakes fish. Maternal serum PCB levels during 

pregnancy were positively associated with the 

number and type of infectious illnesses occurring in infants during the first 4 months of life 

(Smith, 1984; Humphrey, 1988b). The inci4-8 

POPs in the Great Lakes: Human Health Considerations 

dence of infections has also been found to 

correlate with the highest rate of fish consumption (at least three times per month for 3 

years) and with cumulative lifetime fish consumption (Swain, 1991). 

❊ In an older population of sport anglers, 50-90 

years of age, fine motor function skills were 

assessed to determine the effects of exposure 

to PCBs and DDE. This population consisted 

of two groups: (a) high fisheaters who had 

consumed 24 pounds or more of Great Lakes 

sport-caught fish annually for more than 15 

years, and (b) low (or non-fisheaters) who 

consumed less than 6 pounds annually. The 

study demonstrated that serum levels of PCBs 

and DDE were highly correlated, and both 

were significantly higher in high fisheaters 

than in low fisheaters. The mean serum PCB 

concentrations for low versus high fisheaters 

were 6 ppb and 16 ppb, and the maximum 

values were 26 ppb and 75 ppb, respectively. 

The mean serum DDE concentrations for low 

versus high fisheaters were 7.3 and 15.9 ppb, 

with maximum values of 33 and 145 ppb, 

respectively. In the cross-sectional data analyCommercial fishing on the Great Lakes, Duluth, 

Minnesota. 

Photo: Minnesota Sea Grant 

sis, the authors concluded that PCB and DDE 

exposure from consumption of Great Lakes 

fish did not impair fine motor function 

(Schantz et al., 1996). The study also included a longitudinal component, where 

changes in individual scores for motor function over time were postulated to be a more 

sensitive indicator of exposure-related effects 

(Schantz et al., 1999). Recently published 

results of this longitudinal component reported that exposure to PCBs, but not DDE, 

was associated with lower scores on several 

measures of memory and learning in this older 

population of fish-eaters, but not on executive 

visual-spatial or motor function endpoints 

(Schantz et al., 2001). 

Fish and Wildlife Advisories 

States, U.S. territories, and Native American tribes 

issue food consumption advisories in order to protect residents from the health risks associated with 

contaminated noncommercially caught fish and 

wildlife. These advisories, primarily for fish consumption, inform the public on which species to 

avoid or limit eating because of elevated levels of 

pollutants. The advisories apply primarily to noncommercial fish and shellfish obtained through 

sport, recreation, and subsistence activities. Each 

advisory is different: it may recommend no or 

limited consumption; be targeted to everyone or 

limited to women and/or children; or may apply to 

certain species or sizes of fish. The fish advisories 

are submitted annually to EPA and compiled into a 

national listing (www.epa.gov/ost/fish). 

Fish consumption advisories in the United States 

exist for a total of 38 chemical contaminants, but 

most advisories involve 5 primary pollutants: mercury, PCBs, dioxin, DDT, and chlordane. Four of 

these five pollutants are under the Stockholm Convention. The fifth, mercury, is generally emitted to 

the environment as a nonorganic metal, and is 

currently slated for a global risk assessment review 

by the United Nations Environment Programme. 

The number of advisories in the United States 

reported in 2000 (2,838) represents a 7% increase 

from the number reported in 1999 (2,651) and a 

124% increase from the number issued since 1993 

4-9 

 POPs in the Great Lakes: Human Health Considerations 

(1,266) (U.S. EPA, 2001). The national survey 

indicates that 100% of the Great Lakes and their 

connecting waters, and 71% of the coastal waterways, were under advisory in 2000 (Table 4-3). 

The total number of advisories increased for mercury, PCBs, dioxins, and DDT, although often the 

increased number of advisories is considered to 

represent better monitoring of fish contamination 

rather than increased pollution (U.S. EPA, 2001). 

Advisories for PCBs (see Figure 4-3) increased 3% 

from 1999 to 2000, from 703 to 726, and increased 128% from 1993 to 2000 (319 to 726). 

To date, 75% of the 726 PCB advisories in effect 

have been issued by 9 states, 8 of which are Great 

Lakes states (U.S. EPA, 2001). 

The issuance of fish advisories is not a solution to 

POPs pollution, but rather a protective measure 

until pollutant reductions to safe levels can be 

achieved. Indeed, sociobehavioral and demographic data from the Great Lakes region reveal 

substantial nonadherence to fish advisories for a 

variety of reasons, further emphasizing the need 

for POPs pollution prevention at the source rather 

than relying on dietary pathway advisories. 

❊ A recent survey of adult residents of the eight 

Great Lakes states estimated that 4.7 million 

people consumed Great Lakes sport fish in a 

given year, 43.9% of whom were women 

(Tilden et al., 1997). 

❊ Knowledge of, and adherence to, health advisories for Great Lakes sport-caught fish vary 

across different genders and populations, e.g., 

men compared with women, whites compared 

Table 4-3. Fish advisories issued for the Great Lakes 

Great Lakes PCBs Dioxins Mercury Chlordane 

Lake Superior ● ●

Lake Michigan ● ●

Lake Huron ●

Lake Erie ●

Lake Ontario ●

Source: U.S. EPA (2001). 

●

●

●

●

●

●

●

●

Figure 4-3. Fish most affected by PCB advisories: lake 

trout, coho salmon, and carp. 

Credit: The ABC’s of PCBs, University of Wisconsin Sea Grant Institute 

with Native Americans (Fitzgerald et al., 

1996, 1999; Waller et al., 1996; Tilden et al., 

1997). 

❊ 50% of survey respondents who had eaten 

Great Lakes sport fish were aware of the 

health advisory for fish; awareness differed 

significantly by race, sex, educational level, 

fish consumption, and state of residence 

(Tilden et al., 1997). 

❊ 80% of minorities who had eaten Great Lakes 

sport fish were unaware of the fish advisory, 

and awareness was particularly low among 

women (Tilden et al., 1997). 

❊ 97% of Native American men were aware of 

local advisories against consuming Great 

Lakes sport fish. However, 80% of the men 

ate those fish (Fitzgerald et al., 1999). 

❊ Fish is an essential component in the diets of 

many minority populations and Native Americans. These populations consume fish that 

4-10 

POPs in the Great Lakes: Human Health Considerations 

tend to have higher levels of contaminants 

(Fitzgerald et al., 1996; Waller et al., 1996). 

In response to these sociobehavioral and health 

effects findings, advisories now target their message and actions to vulnerable subpopulations, such 

as pregnant women, nursing mothers, and children. There are now 5 categories of consumption 

advisory: (1) no consumption for the general population, (2) no consumption for sensitive subpopulations, (3) restricted consumption advisory for the 

general population, (4) restricted consumption 

advisory for sensitive subpopulations, and (5) a 

commercial fishing ban. The value of strategically 

targeted fish advisories has been demonstrated 

through health education outreach efforts in two 

populations of Native Americans. In these vulnerable communities, body burden levels had been 

elevated two- to eightfold for some POPs. These 

levels were reduced through working with community “gatekeepers” and organizing health fairs and 

public meetings to provide information on cooking 

practices to reduce exposures. The targeted intervention strategies helped to reduce body burden 

levels to U.S. population averages within a 6-year 

period, without sacrificing fish as a nutritionally 

important dietary component (Hicks et al., 2000). 

The continuing need for fish advisories over the 

entire Great Lakes region emphasizes that POPs 

remain a major concern. However, the reductions 

seen for POPs in many places are encouraging. In 

particular, PCB concentrations in fish from the 

Great Lakes region have declined over the years 

(ATSDR, 2000). In 1985, coho salmon from Lake 

Michigan contained 0.99 ± 0.6 ppm of PCBs, 

whereas by 1992 the level was 0.78 ± 0.29 μg/g 

(Eggold et al., 1996). Between 1976 and 1994, 

mean levels of PCBs declined in Lake Ontario 

rainbow trout from 3.9 to 0.97 ppm wet weight 

(Scheider et al., 1998). Similar trends in PCB 

levels were found for other fish species (ATSDR, 

2000). These initial reductions in POPs levels 

following pollution control by industry and through 

government regulation have now, in a number of 

instances, slowed or plateaued, unmasking the 

importance of long-range atmospheric transport as 

a continuing source to the Great Lakes (Figure 

4-4; see Chapter 7, Appendix A). As stated by the 

IJC (1996): 

Figure 4-4. 10-day back trajectories from Rochester, NY, for the year 1999. efers to the likelihood that 

trajectories passed over a given area before arriving at the receptor site. 

Source: Husar and Schichtel (2001). 

Color shading r 

4-11 

 POPs in the Great Lakes: Human Health Considerations 

A successful day’s fishing. 

Photo: ATSDR 

We are increasingly recognizing that a variety 

of pollutants emitted to and transported by the 

air have become the major pathway of pollution to the Great Lakes. These pollutants may 

come from direct sources, ... distant sources 

in North America and beyond... 

Additional detail on the deposition and contribution 

of atmospheric transport loadings to the Great 

Lakes can be found in Deposition of Air Pollutants 

to the Great Waters, Third Report to Congress 

(U.S. EPA, 2000). 

Conclusion 

Adverse effects from POPs have been demonstrated on Great Lakes wildlife and in laboratory 

studies at environmentally relevant levels. Similar 

effects are reported in epidemiological studies of 

human populations with high consumption of 

Great Lakes fish. Many of these vulnerable populations are still being exposed to higher levels of 

POPs than the general U.S. population. These 

findings have national as well as international public health implications because of the known toxicity of these chemicals and their persistence and 

ubiquity in the environment (Hicks et al., 2000). 

The good news is that levels of POPs pollutants in 

the Great Lakes environment have declined dramatically, particularly in the 1970s and 1980s. 

This is a success story of primary prevention, in 

this case pollution prevention through a partnership among federal, state, and local regulatory and 

health agencies, with industry and communities to 

reduce emissions to the environment. More recent 

trends in environmental levels are less clear, indicating a possible plateau and unmasking the importance of inputs from outside the Great Lakes basin 

via atmospheric transport. Further progress in 

reducing exposure levels will require increased 

attention to pollution prevention, particularly toward addressing long-range atmospheric sources. 

Great Lakes sport fish still contain POPs levels that 

are potentially harmful to human health, even 

though two decades of environmental regulation 

have significantly reduced chemical residues in 

waters, sediments, fish, and shellfish (U.S. EPA, 

2001). Considering the societal, cultural, and 

health benefits (Albert et al., 1998) from fishing 

and fish consumption, pollution prevention efforts 

must be maintained consistent with the goal of 

virtual elimination of POPs from the Great Lakes. 

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4-16 

Chapter 5 Alaska—At Risk

To find a diet free from DDT and related chemicals, it seems one must go to a remote and 

primitive land, still lacking in the amenities of 

civilization. Such a land appears to exist, at least 

marginally, on the far Arctic shores of Alaska— 

although even there one may see the approaching shadow. (Rachel Carson, 1962) 

Risks posed by persistent organic pollutants 

(POPs) to Arctic ecosystems and human populations were central to the genesis of the Stockholm 

Convention, and remain a primary concern when 

evaluating potential POPs impacts. For the United 

States, “Arctic ecosystems” means Alaska. Once, 

not too long ago and within the living memory of 

Native Alaskans, the Arctic was a pristine wilderness where POPs were never used and could not 

be detected in wildlife or humans. But the face of 

Alaska is changing, with increasing urbanization, 

industrialization, extractive resource activity, and 

commercial and social contacts with the global 

community. Accompanying these changes are 

concerns that the physical, climatic, and social 

aspects that make Alaska unique—particularly for 

the indigenous population—also make this region 

peculiarly prone to risks from global pollutants. 

Although exposures to 

ronmental media typically remain substantially 

below those found in highly polluted areas of the 

lower 48 United States, but in high-trophic-level 

feeding species—including killer whales and humans—some POPs levels have been recorded that 

are comparable to those found in the general 

United States population and similar marine mammal species. POPs contamination of the Great 

Lakes started as a predominantly regional and local 

phenomenon, and the initial management successes from domestic and binational strategies with 

Canada reflected this scale. For Alaska, however, 

the intervention options mandate a much more 

global approach. From a polar perspective, “close” 

to Alaska and its surrounding waters means the 

huge and growing industrial and population centers 

in Asia, less regulated neighbors just a few miles 

distant in Russia, and sources across the Arctic 

Ocean in Europe that are all closer than Washington, DC (Figure 5-1; polar projections in 

Figures 5-2 and 5-4). 

This review of POPs in Alaska links assessment of 

human health with the state of the environment 

and ecosystems. For Alaska Natives, there is a 

deep connection among the air, the water, the 

animals, and humans. 

POPs are being noted at When people perceive 

this time, their impact will that they are one with 

be more evident in the the environment, and 

future unless pollution the environment is conissues are addressed now. taminated, then they 

also are contaminated. 

As the data to follow This integrated world 

demonstrate, Alaska’s view differs from tradiwildlife and human resi- tional “Western” pracdents are experiencing tice, which has, in the 

POPs contamination past, tended to separate 

from local, regional, and humanity from its supinternational sources. porting ecosystems. 

The levels in most envi- The many similarities in 

Figure 5-1. Map of Alaska. Major roads in red. 

With permission of the National Geographic Society 

5-1

Alaska—At Risk


POPs toxicities between humans and other mammalian species suggest that it would be unwise to 

hold to the belief that humanity is somehow impervious to and distinct from impacts on the supporting ecosystems. 

Why Is Alaska at Special Risk? 

For a variety of reasons, the Arctic ends up as an 

ultimate receptor and “sink” for POPs. The persistence and potential effects of these deposited POPs 

may also be more pronounced in polar climates. 

Factors in evaluating POPs risks to Alaska include: 

❊ Location: The large expanse of the State of 

Alaska, accentuated by its island chains (Aleutians, Pribilofs), means that its neighbors are not 

limited to the great ocean expanses or to 

Canada and Mexico/Caribbean, as is the situation for the other United States. In addition to 

Canada, Alaska’s neighbors are Russia, Japan, 

China, Korea, and other upwind Asian countries. Russia is the nearest trans-Pacific neighbor, only a short kayak excursion away, and 

human and wildlife populations regularly traverse 

these artificial national boundaries. 

❊ Physical climate: Needless to say, winter is cold 

in Alaska, but spring and summer are times of 

relative warmth (Figure 5-2) and rapid biological 

activity. The cycle of prolonged winter darkness 

and cold, followed by warmth and 24-hour light, 

places peculiar stresses on ecosystems. Through 

the winter, mammals rely on fat stores, thereby 

releasing lipid-soluble POPs within their bodies 

as the fat is metabolized. In the spring melt, 

POPs that have accumulated in the ice are released to the food chain during the limited time 

of peak productive and reproductive activity. 

And, throughout all of this, the predominantly 

cold temperatures and permafrost reduce or 

eliminate the microbial activity necessary to 

degrade POPs. 

❊ Ecological sensitivity: Cold temperatures and 

long periods of darkness are associated in the 

Arctic with slow growth, low productivity, and 

low diversity in terrestrial ecosystems. Anthro- ❊ Fat as the currency of life: Survival for all 

pogenic damage to such ecosystems can require species in polar climates rests on securing and 

a long period for recovery. maintaining energy levels. Some animals have a 

Figure 5-2. e profiles: January and 

July. . 

Arctic temperatur

AMAP

5-2

Alaska—At Risk 

round body design with thick layers of insulating 

fat (e.g., fish, seals, walrus, and whales). Another strategy is to secure a regular supply of 

high-energy food, as used by sea otters and 

weasels. Fat is high-energy food. Polar bears 

eat seals by killing them and then stripping off 

and consuming the skin and fat. Likewise, 

brown and black bears catch salmon and strip off 

the skin and fat, which are consumed. Fat becomes the currency for survival in the Arctic. 

Each predator targets the consumption of fat to 

maximize energy transfer. In this process, lipophilic contaminants are passed efficiently up the 

food chain and, at each trophic level, are 

biomagnified, accentuated by both their persistence and volume of consumption. This 

economy includes humans near the top of the 

web, as is evident in the fat rich diet of Alaska 

Natives. 

❊ Human populations: A large proportion of 

Alaskans are indigenous peoples—16% by the 

2000 Census. In the more isolated regions of 

the state, Alaska Natives make up a majority of 

many community populations (Figure 5-3). The 

indigenous population has a greater proportion 

of children than the overall Alaskan population. 

Obtaining wild food is central to the cultural, 

religious, and economic identity and survival of 

these peoples. Through traditional fishing, 

hunting, gathering, and food processing, known 

as subsistence, the culture and society of native 

indigenous populations are maintained. Because 

of concerns about contamination in subsistence 

foods, people turn to the purchase of imported 

foods. This is an economically untenable position in remote Alaskan villages, as well as unfortunate because foods purchased at stores also 

contain POPs (Schecter et al., 1997; Schecter 

and Li, 1997). Subsistence hunting and fishing 

by humans at the top of the food chain also 

relies on high fat intake, including the consumption of other predators, which can compound 

the biomagnification of POPs. Thus, the reliance of Alaska’s people on wild and traditionally 

obtained local foods contributes to Alaskans’ 

concerns regarding international sources of 

pollution (Hild, 1995). 

Figure 5-3. Total and indigenous populations of Alaska. 

AMAP. 

❊ Previous absence of contamination: Compounding Alaska’s susceptibility is the recognition that its remote areas were previously uncontaminated, with little to no local use of POPs 

pesticides and industrial pollutants except around 

urban settlements and military bases (Durham et 

al., 1961; Hayes et al., 1958). Any contamination comes in stark contrast to the expected 

purity, even if Alaskan levels remain below those 

in the lower 48 States. There is significant 

economic value in safeguarding this food supply, 

and likely more so in the future. This is particularly significant for a region such as Alaska 

where primary production (e.g., seafood) exports 

to the rest of the United States and the world are 

central to economic prosperity. Approximately 

2 million tonnes of seafood are harvested annually from the Bering Sea alone, and over 80% of 

the world’s wild salmon are supplied by Alaskan 

fishermen. 

5-3

Alaska—At Risk


POPs Transport to Alaska 

POPs are transported through the environment to 

Alaska through the movement of air, water, and 

migratory species (e.g., fish, birds). These processes are anticipated under the Stockholm Convention and elaborated upon in Chapter 7 of this 

report. Many physical aspects of the circumpolar 

region now appear to contribute to a natural 

transboundary movement of POPs to Alaska. Review of these pathways in the context of a global 

treaty must not, however, be interpreted as overlooking the contribution of other regional or local 

sources. Although Alaska has not had industrial 

POPs manufacturers, there are incidents of past 

usage that include military sites (e.g., PCBs) and 

mosquito control efforts (e.g., DDT). Some local 

waste burning may contribute byproducts (e.g., 

polychlorinated dioxins and furans). These are 

under further domestic and local investigation, and 

source reduction strategies are taking place. 

Atmospheric Transport 

Atmospheric air patterns move pollution from 

around the Northern Hemisphere into the Arctic 

(Figure 5-4; see also AMAP Arctic atmospheric 

circulation maps with additional detail and seasonal 

effects at www.amap.no). Winds blow in the 

midlatitudes from west to east, bringing Asian air 

into southern and central Alaska. During Russian 

and Chinese nuclear testing in the 1960s and 70s, 

Alaskans were concerned because they were a 

short distance downwind. At the same time, in the 

For global distillation, a number of the POPs are 

considered “semivolatile,” evaporating in warmer 

climates, moving north (or south) and then precipitating out in colder climates. This cycle can repeat 

itself, moving materials poleward in a process 

known as the “grasshopper” effect (or global fractionation and cold condensation) (AMAP, 1998; 

Mackay and Wania, 1995; Wania and Mackay, 

1993). In addition, all POPs can move to the 

Arctic through episodic events that move dust 

particles long distances. As demonstrated through 

back-trajectory mapping and satellite imagery 

(Chapter 7), Alaska is downwind of many Asian 

and European sources. 

The atmospheric peculiarities of the Arctic, and the 

impact of global pollution, are most evident 

through the phenomenon of Arctic haze. Arctic 

haze is predominantly attributed to the movement 

of sulfur oxides, hydrocarbon gases, and particles 

north from their industrial sources. In the 1970s, 

Matthew Bean, an Alaska Native Yupik elder from 

Bethel, recognized that the plants were not as 

green, the sky not as blue, and the horizon not as 

clear as when he was a boy. He soon found himself talking with academic researchers who corroborated his observations with their air quality 

measurements. Arctic haze did exist (Rahn and 

Lowenthal, 1984; Shaw et al., 1993). Further 

research determined that this haze not only contained pollution from the far north, but contaminants from all over the northern half of the globe. 

high latitudes of northern The haze from these 

Alaska, winds blow from materials becomes 

the east to the west, increasingly dense durbringing pollution from ing the cold, dark winnorthern and western ter. In the spring, the 

Europe. higher angle of the sun 

warms the air, deepenAs detailed in Chapter 7, ing the mixing layer and 

air movement can lead to depositing pollutants on 

POPs transport and the earth’s surface. The 

deposition in two basic return of the sun also 

ways: global distillation initiates a number of 

of semivolatile chemicals, biological activities and 

and mass transport and unique photochemical 

deposition of POPs at- phenomena (Lindberg 

tached to dust and soot. et al., in press) leading 

Figure 5-4. Atmospheric transport pathways to the Arctic 

(Crane and Galasso, 1999, map 3). 

5-4

Alaska—At Risk 

to the “Arctic sunrise” effect. The deposition, 

availability, and metabolic uptake of global contaminants into Alaska’s plants, animals, and people 

generally coincides with the commencement of 

spring biological activity. 

Hydrologic Transport 

The very low water solubility of most POPs— 

counterbalancing their high lipid solubility—leads 

to water transport predominantly attached to fine 

particles. However, some organic pollutants, such 

as the hexachlorocyclohexanes (e.g., lindane) are 

more soluble in water and can be transported 

through a combination of prolonged persistence 

in cold waters and large volumes of oceanic water 

movement. Hydrologic pathways are also interconnected with atmospheric transport through the 

semivolatile nature of POPs, where contaminants 

can exchange between environmental media. 

For Alaska, a combination of riverine and oceanic 

transport can bring POPs from long distances. 

The major rivers draining the agricultural and 

industrial areas of Russia flow into the Arctic 

Ocean. A number of Russian rivers are known to 

have readily detectable levels of various pesticides, 

including DDT, that do not appear to be decreasing over time (Zhulidov et al., 1998). These rivers 

release POPs to the Arctic Ocean, after which 

contaminants can be transported by the prevailing 

currents generally westward from the contaminated 

Ob and Yenisey Rivers, and eastward from the less 

contaminated Lena River. 

Oceanic currents in the Pacific also provide a 

transport pathway for contaminants (Figure 5-5). 

After contaminants have traveled down rivers and 

into the ocean from agricultural fields and industrial areas of Southeast and Central Asia, the 

western Pacific currents can carry these contaminants to other parts of the world. The currents 

move along Japan, Korea, and Russia, and finally 

flow through the Bering Sea and into the Arctic 

Ocean (AMAP, 1998). Surface water studies of 

PCBs have identified this movement and the 

accumulation of materials within the Bering Sea 

(Yao et al., 2001). Work from Japan on the 

“Squid Watch Program” is tracking the moveFigure 5-5. Ocean currents impacting Alaska. 

Source: Adapted with permission from Apel, 1987; NOAA. 

ments of POPs in the North Pacific driven by the 

prevailing west wind and the Kuroshio warm 

current (Hashimoto et al., 1998). 

Migratory Species 

Transport of contaminants from other regions of 

the globe to the food supply of Alaska Natives and 

other Americans can also occur through the movement and harvesting of migratory species. The 

springtime return of waterfowl is the first fresh 

meat many Alaska Natives have after a long winter 

of eating dried meat and stored foods. In addition 

to adult birds, eggs are also collected and consumed. Some of these birds have wintered in Asia 

and Central America. In those regions, feeding 

areas (such as fallow fields) may have been sprayed 

with organochlorine insecticides. The bodies of 

birds can carry pollutants that may be banned in 

the American communities that consume them 

(Figure 5-6). 

Migratory fish do not travel as far as migratory 

birds, but the mechanism for accumulation of contaminants is similar. Recently, it was shown that 

the very low concentrations of HCB, s-DDT, and a 

number of PCB congeners detected in sockeye 

(red) salmon returning to interior Alaskan lakes can 

5-5

Alaska—At Risk


Figure 5-6. Migration routes of land, lake, and wetland birds (Crane and Galasso, 1999, Map #9). 

contribute more POPs to the lake ecosystem than 

the amount contributed by atmospheric deposition 

(Ewald et al., 1998). No studies to date have assessed the sources of chemicals that might be 

found in low levels in fish species such as salmon, 

capelin, and pollock that range in the Bering Sea 

between the United States and Russia. These 

commercial fish species end up on tables throughout the world, and all have come from an international ocean that receives water from the Western 

Pacific and Asia (Crane and Galasso, 1999) 

(Figure 5-7). 

Further up the food chain, migratory marine mammals cover large areas, consuming a variety of food 

sources. These sources in turn lead to different 

levels of POPs biomagnification. Most seals, sea 

lions, toothed whales, and polar bears are near the 

top of the food chain and move among international waters (Crane and Galasso, 1999). Animal 

species feeding lower on the food chain generally 

have corresponding lower levels of POPs overall, as 

well as different specific chemicals. Walrus and 

bearded seals feed on benthic populations and 

therefore have a different POPs profile than predators that feed on fish or other marine mammals. 

Ringed seals eat crustaceans and fish. Likewise, 

filter-feeding whales, such as bowhead whales, feed 

low on the food chain, eating krill, and have a very 

different POPs profile and lower levels overall than 

the upper trophic level feeders. 

POPs Levels in Alaska 

Insights into levels and potential risks from POPs in 

Alaska are best gained through comparing exposure data to either effect levels in species of concern or to levels found in the lower 48 States. 

Figure 5-7. Migration routes of salmon (Crane and 

Galasso, 1999, Map #13). 

5-6

Alaska—At Risk 

Although zero levels would be the preferred value 

for all of the POPs, it must be recognized that with 

the global distribution of these pollutants, their 

persistence, and modern laboratory equipment, 

scientists will invariably be able to detect some level 

of pollutant, especially in species higher on the 

food chain. This complexity is compounded by the 

multiple environmental media and species in which 

measurements are taken, and the multiple POPs 

and their metabolites under consideration. Care 

must also be taken in comparisons between different studies because units of measurement, analytic 

protocols, and methods of reports may vary. 

For this report, we compare levels found in Alaska 

to those in the lower 48 States and, where possible, to the effect levels found in these or similar 

species from other areas of the United States. 

Reflecting the integrated nature of the Alaskan 

situation, the species discussion commences with 

wildlife, proceeds through wildlife that are used as 

food, and concludes with human consumers. For 

those seeking additional details on species levels 

across the Arctic, excellent references are available 

in AMAP (1998), Canadian Northern Contaminants Program (Jensen et al., 1997), Landers and 

Cristie (1995), and Ritter et al. (1995). 

Wildlife Levels 

Bald Eagle 

Bald eagle. 

Photo: U.S. Fish and Wildlife Service 

The decline of bald eagle populations to the verge 

of extinction in the lower 48 States is emblematic 

of the effect of POPs, DDT/DDE in particular. 

Although residual DDE contamination continues to 

affect reproductive rates in some areas, the recovery of bald eagle populations in the lower 48 States 

following the cessation of DDT use and protection 

as an endangered species has been a remarkable 

Figure 5-8a,b. Bald eagle levels of DDT and PCBs in the Aleutians (Anthony et al., 1999), geometric mean 

values. 

5-7

5-8

Alaska—At Risk

success. 

remained robust, with DDT/DDE levels generally

well below the potential effect level of ~3.6 μg/g

DDE (Anthony et al., 1999; Wiemeyer et al.,

1993). anana River in

the interior of Alaska in 1990-91 had DDE levels

below concentrations known to result in sublethal

or lethal effects, and most organochlorine concentrations were an order of magnitude lower than

concentrations in bald eagle eggs from elsewhere in

the United States (Richie and Ambrose, 1996).

However, even in the presence of this apparent

success there are warning signs. 

western Aleutian Islands have been found to have

ratios of DDT/DDE that indicate new DDT

sources, and DDE levels in some eggs on one

island (Kiska) may be depressing reproductive success (Anthony et al., 1999; Estes et al., 1997)

(Figure 5-8). 

known, the prey species, especially migratory birds

from Asia where DDT is still used, need to be

assessed further. 

though DDE is suspected as the causative agent in

the above-mentioned studies, DDE concentrations

in eagle eggs were positively correlated with other

organochlorines, including oxychlordane, betaHCH, dieldrin, and hexachlorobenzene.

Peregrine Falcon

Historic declines in peregrine falcon populations at

several locations, including Alaska, have been

correlated with DDE concentrations in their eggs

causing eggshell thinning and hatching failure

(Ambrose et al., 1988a,b; 2000). 

centrations of ~15-20 ppm p,p ́-DDE have been

associated with a 20% eggshell thinning in peregrine falcons (Peakall et al., 1990). 

are expected to decrease if eggshells are at least

17% thinner than pre-DDT measurements (Kiff,

1988). n

Alaska declined during the 1960s, stabilized in the

mid-1970s, began to increase in the late 1970s,

and have since stabilized or continued to increase.

Eggs from two subspecies of peregrine falcons

were collected from interior and northern Alaska

between 1979 and 1995 and analyzed for orgaFigure 5-9a,b. Time trends for DDE and PCBs in Alaskan

peregrine falcon eggs (Ambrose et al., 2000). Geometric

mean and range. (n = 19–32)

Peregrine falcon.

Photo: U.S. Fish and Wildlife Service

ppm wet weight ppm wet weight

In Alaska, bald eagle populations have

Eagles nesting along the T

Eagles in the

Although the sources are not yet

It also should be noted that alThreshold conPopulations

Peregrine falcons in interior and norther
Alaska—At Risk 

nochlorine compounds and metals (Ambrose et al., 

2000) (Figure 5-9). This study represents one of 

the few relatively long-term data sets from Alaskan 

biota and can offer some insight into POPs residue 

trends with time. In general, organochlorines 

declined over time, although the trend was not as 

strong for PCBs, which declined more slowly. 

These results agree with trends observed in other 

peregrine falcon populations, which show that 

PCB concentrations have not decreased as clearly 

as other organochlorine compounds (Peakall et al., 

1990; Newton et al., 1989; Johnstone et al., 

1996). Although organochlorine levels have decreased over time, evidence for cumulative and 

single-contaminant reproductive effects was found 

in remote locations (Ambrose et al., 2000). Contaminant monitoring remains a necessary management tool for this species, which is recovering from 

near extinction caused largely by environmental 

contaminants, and continues to remain vulnerable 

to persistent and bioaccumulative compounds. 

Killer Whale 

Killer whales spy-hopping. 

Photo: Craig Matkin 

Certain populations of killer whales (Orcinus orca) 

have been extensively studied over the past 30 

years, including populations in Puget Sound, Washington, the inside waters of British Columbia, 

Southeastern Alaska, and Kenai Fjords/Prince 

William Sound, Alaska. The POPs concentrations 

found in some populations of Alaskan killer whales 

are similar to those recently reported in pinnipeds 

and cetaceans that occur in more contaminated 

waters (Ylitalo et al., 2001). Levels of total PCBs 

in blubber ranged up to 500 ppm, and total DDTs 

ranged up to 860 ppm, while median levels and 

some group levels were significantly lower (Figure 

5-10). Concentrations of POPs in transient killer 

whale populations (marine mammal-eating) were 

much higher than those found in resident animals 

(fish-eating), apparently because of differences in 

diets (amounts and types of fat consumed) and 

feeding locations (localized or broad-ranging) 

(Ylitalo et al., 2001). Both resident and transient 

whale groups described in the report reside in 

Alaskan waters, although the transient pods may 

move hundreds of miles up and down the coast 

beyond Alaska and through international waters. 

Figure 5-10. 

resident v. transient killer whales (Ylitalo et al., 2001). 

Mean denoted by horizontal line, range as vertical bar. 

Dioxin TEQ and sum-DDT in Alaskan 

5-9

Alaska—At Risk


Life-history parameters such as sex, age, and reproductive status also influence the concentrations 

of POPs in Alaskan killer whales. Reproductive 

female whales contain much lower levels of POPs 

than sexually immature whales or mature male 

animals in the same age class. This is likely due to 

transfer of POPs from the female to her offspring 

during gestation and lactation. Birth order also 

influences the concentrations of POPs. Adult 

male, resident, first-born whales contain much 

higher POPs concentrations than are measured in 

subsequent offspring to resident animals in the 

same age group (Ylitalo et al., 2001). There is also 

some evidence of decreased survival of the firstborn 

transients that have the highest POPs levels 

(Matkin et al., 1998, 1999). 

Reports of POPs levels in killer whales have been 

associated with decreases in reproductive success 

(Matkin et al., 1998, 1999). The causal factors for 

low reproduction and population decline of certain 

transient groups of killer whales from Prince William Sound/Kenai Fjords are not known. The low 

reproduction and population decline may be a 

natural cycle, related to human factors (e.g., oil 

spill), exposure to natural toxins (e.g., biotoxins), 

decline in the primary prey species (harbor seal), or 

a combination of environmental and anthropogenic 

factors. Exposure to toxic POPs may also be a 

contributing factor (Ylitalo et al., 2001). 

Sea Otter 

Sea otters. 

Photo: Craig Matkin 

Sea otters have declined precipitously throughout 

the Aleutian Islands over the past decade (Estes et 

al., 1998). Although investigations to date suggest 

predation may be the primary cause of the decline, 

contributing factors such as contaminants have not 

been completely ruled out. Sea otters at several 

Figure 5-11a,b. 

(n=7), Southeastern Alaskan (n=7), and California (n=9) 

sea otters (Bacon et al., 1999). Mean values. ppm wet weight liver 

Comparison of POPs levels in Aleutian 

5-10

Alaska—At Risk 

isolated sites in the Aleutians (Adak, Shemya) have 

been recorded with elevated levels of certain POPs, 

particularly PCBs (Giger and Trust, 1997). PCB 

levels in sea otters from the Western Aleutian Islands (Adak and Amchitka Islands) were somewhat 

higher than levels found in California sea otters, 

and were significantly elevated relative to PCB 

concentrations in sea otters from southeast Alaska 

(Bacon et al., 1999) (Figure 5-11). The relative 

contribution to PCB levels in Aleutian sea otters 

from long-range sources compared to local contamination from old defense sites cannot be ascertained using currently available data (Bacon et al., 

1999; Estes et al., 1997). Sum-DDT levels in 

Aleutian otters, although much higher than the 

very low values found in Southeast Alaska, remain 

substantially lower than in California otters. These 

sum-DDT concentrations were not in the range 

that causes reproductive impairment in captive 

mink, a commonly used comparison and related 

species. However, there is little information that 

can help evaluate whether there may be interactive 

effects among POPs and other stressors affecting 

Aleutian sea otters. 

Species Consumed by Humans 

Beluga 

Beluga whales (Delphinapterus lucas) are a preferred food for many Alaska Natives. The muktuk 

(the skin and outer layer of fat) is considered a 

choice item for consumption. This outer layer of 

fat contains the highest levels of POPs in the animal (Wade et al., 1997). The blubber of beluga 

whales from Alaska contains POPs in concentration ranges similar to those found in beluga whales 

from the Canadian Arctic (Muir and Norstrom, 

2000) but much lower than levels in whales from 

the highly contaminated St. Lawrence River in 

eastern Canada (Krahn et al., 1999) (Figure 5-12). 

Within Alaska, the low levels in the Cook Inlet 

stock are noteworthy, as these animals reside in 

Figure 5-12. Sum-DDT levels in beluga blubber. Mean (●) +/– one standard deviation (vertical bar) (Becker 

et al., 2001). 

5-11

Alaska—At Risk


Beluga whales. 

Photo: NOAA 

one of the most “urban” areas of Alaska, where 

anthropogenic contamination could be expected to 

result from the relatively higher density of human 

residents and commercial activities (Krahn et al., 

1999). 

Gender is an important factor to consider when 

interpreting differences in POPs concentrations 

among beluga whale stocks (Krahn et al., 1999). 

For example, the adult males of each stock had 

higher mean concentrations of all contaminant 

groups than did the adult females of the same 

stock. This is considered to be an effect of POPs 

transfer from the mother to the calf during gestation and lactation. This theory is supported by the 

finding that upon reaching sexual maturity, the 

levels of toxaphene, PCBs, DDTs, and chlordane 

steadily go down in females as they produce calves 

and lactate (Wade et al., 1997). 

Bowhead Whale 

The bowhead whale stock (Balaena mysticetus) 

migrates through the Bering, Beaufort, and 

Chukchi Seas and is listed as an endangered species. Alaska Natives are the only U.S. citizens 

permitted to harvest the bowhead whale for food. 

Studies have shown relatively low levels of PCBs in 

bowhead whale (Figure 5-13) blubber, but these 

levels tend to increase with age (McFall et al., 

1986; O’Hara et al., 1999). Previous reports 

support the view that these large filter-feeding 

whales, consuming at a lower level on the food 

chain, have lower concentrations of POPs in their 

Bowhead whales. 

Photo: NOAA 

blubber. Toothed whales, eating higher on the 

food chain, may have one or two orders of magnitude more POPs than the filter-feeding whales 

(O’Hara and Rice, 1996; O’Shea and Brownell, 

1994; Borell, 1993). 

Figure 5-13. POPs levels in bowhead whale blubber 

(O’Hara et al., 1999). Mean values. n=26. 

Seals 

The various seal species in Alaska constitute a 

substantial portion of the marine mammal diet of 

numerous predator species, including humans. 

Blubber samples from four Alaskan seal species 

(bearded seal, Erignathus barbatus; harbor seal, 

Phoca vitulina; northern fur seal, Callorhinus 

ursinus; ringed seal, P. hispida) have been col5-12

Alaska—At Risk 

Northern fur seals. 

Photos: Suzanne Marcy 

lected and analyzed for POPs contaminants (i.e., 

total PCBs, total DDTs, total chlordanes, HCB, and 

dieldrin) (Krahn et al., 1997). Harbor seals, frequently consumed by Alaska Natives, were found to 

have low but measurable levels of several of these 

POPs (Figure 5-14). The concentrations of POPs 

in harbor seals from Prince William Sound were 

generally much lower (e.g., total PCBs up to 100-

fold and total DDTs up to 30-fold lower) than those 

recently reported for harbor seals from the northwestern U.S. mainland, including animals involved 

in mass mortality events (Krahn et al., 1997) (see 

Chapter 6, Marine Ecosystems). For Alaska, however, in contrast to other parts of the United 

States, the potential for POPs biomagnification 

continues through the consumption of harbor seals 

by humans, an additional one or more trophic 

levels higher. 

Notable among the multiple studies of seal species 

is the finding that POPs concentrations in male 

subadult northern fur seals sampled in 1990 at St. 

Paul Island in the Bering Sea were higher than 

Figure 5-14. est Coast U.S. 

harbor seals (Papa and Becker, 1998). efix 

indicates summation of related chemical substances. 

POPs levels in Alaskan v. W

The “s” pr

concentrations in the ringed and bearded seals 

from the Bering Sea or in the harbor seals from 

Prince William Sound. Fur seals feed mainly on 

oceanic species such as squid and pollock. Female 

and juvenile fur seals migrate long distances into 

the open ocean of the northern Pacific far south of 

Alaska and even to the shores of Japan, as well as 

California. The higher POPs concentrations in fur 

seals are consistent with exposures occurring during these long oceanic migrations. Harbor seals 

feed on different species of fish that tend to be very 

coastal, like perch. Harbor seals do not migrate, 

but stay close to their coastal feeding and haul-out 

areas. 

Steller Sea Lion 

Steller sea lions. 

Photo: NOAA 

Studies show that PCBs are the predominant POPs 

in sea lion blubber, followed by levels of DDT/ 

DDE. Levels of chlordane compounds were an 

order of magnitude lower. Higher concentrations 

of PCBs and DDTs were found in Steller sea lions 

from Alaska compared to those from the Bering 

Sea, indicating that the populations have different 

sources of exposure (Lee et al., 1996). Like beluga 

whales, as Steller sea lion females become sexually 

mature they show a dramatic decline in POPs 

levels. It has been calculated that they may lose 

80% of their PCBs and 79% of DDT/DDE through 

lactation while nursing the first pup (Lee et al., 

1996). Two studies of PCBs in Steller sea lion 

blubber found an average of 23 ppm (Varanasi et 

al., 1993) and 12 ppm in males (Lee et al., 1996). 

5-13

Alaska—At Risk


These PCB levels in Steller sea lions generated 

concern among local subsistence populations, who 

requested an evaluation of potential human health 

impacts (Middaugh et al., 2000a,b; see following). 

Salmon 

Alaskan fisher and sockeye salmon. 

Source: NOAA 

Salmon species are key to Alaska’s commercial 

fisheries and to the well-being of many subsistence 

communities. For the Alaskan fishing industry, 

salmon is a billion-dollar business. For subsistence 

communities who catch and consume their own, 

fish by weight make up about 59% of the total 

subsistence harvest for Alaska Natives, with salmon 

being the most important species (AMAP, 1998). 

In western Alaska, the fish harvest can approach 

220 kg (485 lb) per person per year and make up 

more than 73% of all locally harvested food (Wolfe, 

1996). The U.S. Fish and Wildlife Service and 

Alaska state government are currently assessing 

contaminant levels and evaluating fish health in 

salmon from selected Alaskan rivers. 

The migratory and reproductive patterns of sockeye salmon (Oncorhynchus nerka) are known to 

provide a means of transport for very low levels of 

chemicals such as PCBs and DDT to waters used 

by other species of Alaskan freshwater fish, such as 

grayling (Thymallus arcticus) (Ewald et al., 1998). 

Migrating salmon carry these low but measurable 

levels of POPs to spawning areas where, after 

spawning, they die and decay. The POPs then 

become bioavailable to other local species. The 

levels of POPs delivered by salmon to Alaskan 

interior lakes and rivers have been estimated to be 

slightly above the levels deposited through atmospheric means, although these levels are far below 

those found in fish from the Great Lakes region 

(Figure 5-15). 

Figure 5-15. eliminary 

Alaskan results overlaid AMAP summary figure (Ewald et 

al., 1998; Allen-Gil et al., 1997). 

lake trout from Elusive, Feniak, and Schrader Lakes in 

northern Alaska (Allen-Gil 

concentrations in sockeye salmon from the same run in 

Alaska, taken at the coast and upstream lake, where PCB 

concentrations have increased as lipids have been 

metabolized during the migration (Ewald et al., 1998). 

PCB levels in salmonid fish: pr

Mean concentrations in 

et al., 1977). Mean 

5-14

Alaska—At Risk 

Polar Bear 

Polar bear. 

Photo: U.S. Fish and Wildlife Service 

Polar bears are at the top of the Arctic marine food 

web. Norstrom et al. (1998) investigated chlorinated hydrocarbon compounds in polar bears from 

much of the circumpolar Arctic. They found 

strong relationships among contaminant concentrations and sex. Individual dietary preferences, regional differences in species availability, and foodchain structure also contributed to variability within 

the data. For example, baleen whale and walrus 

carcasses may be seasonally important food 

sources for polar bears in the Bering Sea and 

Chukchi Sea region, supplementing their primary 

diet of ringed and bearded seals. Walrus (except 

when eating seals) and baleen whales feed at lower 

trophic levels than other Arctic marine mammal 

species. Conversely, polar bears feeding on beluga 

carcasses in eastern Canada exhibit higher POPs 

levels. Thus, prey selection can affect the pattern 

of chlorinated hydrocarbon uptake in these different polar bear populations. Total chlordanes (sum 

of 11 chlordane-related compounds) were the most 

uniformly distributed POPs in this study, reflecting 

a similar pattern found in air and seawater sampling (Norstrom et al., 1998). 

Although sample sizes were small, concentrations 

of total PCBs, total chlordanes, DDE, and dieldrin 

in polar bears from the Bering, Chukchi, and western Beaufort Seas tended to be among the lowest 

in the study area. The atmospheric circulation of 

this area is dominated by eastward airflow from 

Asia and the North Pacific Ocean. Sources of 

POPs in the Bering, Chukchi, and western Beaufort Seas are, therefore, more likely to have originated in eastern Asia. PCBs were generally used 

less often in Asia, except Japan, than in North 

America and Europe (Norstrom et al., 1998). The 

U.S. Fish and Wildlife Service, Office of Marine 

Mammal Management, continues to work with 

Alaska Native hunters to collect samples for analysis of environmental contaminants. 

Native Peoples of Alaska 

Alaska Native child with eggs—a subsistence food. 

Family photo: Jesse Paul Nagaruk 

Food is central to culture. Alaska Natives, although 

sharing different cultural heritages, are linked to 

their environment through the foods that they 

gather locally and consume. The social structures 

that define behavior in the sharing of subsistence 

harvests and through feasts are the traditions of 

Alaska Natives—the cultural values of the people. 

Children and youth are taught about their environment and about their relationship to the community through hunting, fishing, gathering, and sharing. The survival knowledge of the group is passed 

5-15

Alaska—At Risk


down from generation to generation, ensuring the 

transmission of language and values. The work of 

obtaining one’s own food is rigorous and promotes 

self-reliance and self-esteem. For all of these factors, continued confidence in the quality of locally 

obtained foods is essential (Egeland et al., 1998). 

Alaska Natives eat 6.5 times more fish than other 

Americans (Nobmann et al., 1992). Under the 

Marine Mammal Protection Act, Alaska Natives are 

the only people in the United States allowed to 

hunt marine mammals, which they then eat. By 

doing so, Alaska Natives consume predator species 

(seals, sea lions, bears, and toothed whales) at the 

very top of the food chain. Many Alaskans have 

wide seasonal variation in their dependence on 

locally available foods. Their diet shifts in response 

to short intense summers and the migration of wild 

birds, fish, and mammals. Alaska Natives eat more 

fat, albeit different types, than most U.S. citizens. 

Marine mammal fats and fish oils differ significantly 

from pork and beef fats in their ability to provide 

health benefits (Jensen and Nobmann, 1994; 

Nobmann et al., 1992; Scott and Heller, 1968). 

Estimates of the amount and type of subsistence 

foods consumed by Alaska Natives are summarized 

in Figure 5-16, documenting levels of dependence 

and species preferences by area. 

In regions where employment opportunities are 

scarce or seasonal, locally obtained foods remain 

an economic necessity. Shifting food consumption 

in remote Alaskan communities is not beneficial for 

several reasons. Food that is purchased is expensive and rarely fresh owing to the long distances it 

must be shipped and the number of times it must 

be handled as it goes into smaller and smaller 

stores. Many people in these remote communities 

have very limited food budgets because of the 

scarcity of jobs and high costs of heating and other 

costs associated with life in a remote and challenging environment (Egeland et al., 1998). 

Store-bought foods in remote Alaskan communities 

need to have a long shelf life. Therefore, the foods 

have been frozen, canned, or chemically preserved. 

Many of these foods do not have the nutritional 

value of fresh foods from the local area. StoreFigure 5-16. Total and composition of subsistence 

production in Alaska. AMAP. 

bought foods are much higher in processed sugars, 

saturated fats, sodium, and simple carbohydrates, 

contributors to such conditions as obesity, diabetes, 

heart disease, and dental caries. These conditions 

are growing at alarming rates in Alaska (APHA, 

1984; Ebbesson et al., 1996; Lanier et al., 2000; 

Nobmann et al., 1992; Nobmann et al., 1998; 

Nutting, 1993; Schraer et al., 1996). Health surveys have also indicated that, in some communities, the individuals who are most concerned about 

environmental pollution are the same people who 

most frequently consume less traditional foods and 

are shifting to buying food from the store (Dewailly 

et al., 1996; Egeland et al., 1998; Hild, 1998). 

Adding to concerns about contaminants in local 

foods, Alaska Natives have reported changes in the 

subsistence species they hunt. These changes 

include seals with diseases they have not seen 

before, no hair, yellow fat, fat and meat that does 

not taste as it should, and seals with abnormal 

5-16

Alaska—At Risk 

growths and abnormal sex organs. Similar concerns have been raised about other subsistence 

species. These observations, collected now by the 

Alaska Native Science Commission, may contribute 

to an understanding of what is occurring in the 

changing Arctic (www.nativeknowledge.org). In 

the absence of key information to answer specific 

questions, and in response to media reports about 

contamination of the Arctic, the conclusion being 

reached by many Alaska Natives is that the animals 

may not be healthy, and the health of their children 

may be at risk. 

POPs Levels in Alaska Natives 

Most of the POPs under the Stockholm Convention were never used in or near Alaska. For the 

other POPs (e.g., PCBs, DDT, polychlorinated 

dioxins/furans), local use in Alaska and emissions 

to the environment are much less than has occurred in the lower 48 states. Yet there is considerable concern among residents—particularly Alaska 

Natives—that they may have become contaminated 

through consuming traditional foods. The most 

expeditious way to assess the extent to which Alaskans have been exposed to these persistent toxic 

substances is to measure levels in human tissue 

(Hild, 1995). Unfortunately, there is no statistically 

based survey of POPs levels in Alaskans. Indeed, 

there is no national statistically based survey of 

POPs levels in the U.S. population, although serum 

has been collected under the NHANES IV study 

and is being analyzed at the Centers for Disease 

Control and Prevention (CDC). 

POPs levels have been measured in small studies of 

selected Alaska Natives, lower-48 background 

comparison groups, and Great Lakes fishers, providing valuable indicative and comparative information on POPs levels (Figures 5-17 and 5-18). 

These data can help inform hypotheses and conclusions regarding sources of human exposure to 

POPs and the resulting concentrations and trends. 

For example, as with marine mammal exposures, 

high trophic level feeding is generally more problematic than lower on the food chain. Thus, it can 

be hypothesized that Alaska Native diets based on 

plants and plant-eating animals are of less concern 

Figure 5-17. 

concentrations (TEC) in Aleutian volunteers (n=48) 

compared with Arkansas (n=70) and Great Lakes fisher 

(n=31) comparison groups (Middaugh et al., 2000a). 

Serum dioxin toxicity equivalence 

than those relying on the consumption of marine 

mammal predator species. The importance of 

location and proximity to emission sources and 

transport pathways can also be evaluated, as the 

western Aleutians represent a quite different locale 

from the Beaufort Sea off northeastern Alaska. 

Likewise, the subject's age may be a major determinant of many POPs levels. As has been evident 

in lower-48 studies, POPs levels tend to increase 

with age because of the fundamental persistent and 

bioaccumulative nature of the contaminants, espeFigure 5-18. 

populations (Middaugh et al., 2000b, 2001; pers. comm. 

C. Rubin 2002 for median levels in Alaska Native women). 

n=166 (Aleuts); 131 (Alaska Native); 180 (Arkansas); 

30 (Great Lakes). Results not lipid adjusted. 

POPs levels in Alaskan v. comparison U.S. 

5-17

Alaska—At Risk


cially in males where there is no excretion through 

lactation. Age is also an important consideration 

in evaluating Alaska Native levels, as dietary practices and the proportion of traditional foods in 

many diets have changed over recent years. 

In response to citizen concerns, the State of 

Alaska, Department of Health and Social Services, 

conducted a targeted study of POPs in five Aleutian 

communities (Middaugh et al., 2000a,b, 2001). 

These communities had become concerned because some Alaskan Steller sea lion blubber had 

been reported to contain relatively high levels of 

PCBs (23 ppm, Varanasi et al., 1993; 12 ppm in 

males, Lee et al., 1996) potentially impacting their 

use of sea lions as a source of meat and oil. As 

graphed in Figure 5-17, total PCB, dioxin, and 

furan toxicity equivalence concentrations (TEC) 

levels in the Aleutian volunteers (Middaugh et al., 

2001) were similar to those in the background U.S. 

population (Arkansas) and considerably below 

fisher exposures on the Great Lakes (Anderson et 

al., 1998). Middaugh et al. (2000a) also analyzed 

the age relationship to concentration levels (Figure 

5-19), demonstrating increased POPs levels with 

age. Similar age-related findings are evident in 

other studies from lower-48 populations and cannot necessarily be ascribed to dietary pattern 

changes. Because the Aleutian sample sizes were 

very low and from volunteer populations in isolated, select communities, few conclusions can be 

drawn, and a broader surveillance is needed to 

Figure 5-19. Distribution of serum PCB concentrations in 

Aleutian volunteers as a function of participant’s age 

(Middaugh et al., 2000a). 

answer key questions and address community 

concerns. 

A small group of Aleut women of childbearing 

age—not pregnant at the time—was identified in 

the Middaugh et al. (2001) study. If their levels 

were to be compared with the maternal plasma 

study data of the Arctic Monitoring and Assessment Programme (AMAP, 1998), the Aleut women 

would have the highest levels of p,p'-DDE (geometric mean 0.503 ppm lipid) so far found in the 

circumpolar region. They were second highest 

among the other Arctic nations for trans-nonachlor 

(g. mean 0.0498 ppm lipid) and oxychlordane (g. 

mean 0.0285 ppm lipid) (Middaugh et al., 2001). 

Note, again, that the Aleutian studies are only 

preliminary and cannot be considered statistically 

representative of this population. The relative 

elevations of DDT and chlordane derivatives are, 

however, consistent with the location of the Aleutians near continuing use regions for these POPs in 

Asia. 

From the other side of Alaska, Arctic Slope mothers have POPs levels (DDT, DDE, mirex, transnonachlor, oxychlordane, and PCBs) that are lower 

than those in the Aleutian/Pribilof Islands women 

of childbearing age (Simonetti et al., 2001). These 

levels are comparable with levels in the lower 48 

states for background populations (Anderson et al., 

1998). 

At this time, POPs movement and deposition 

trends to the north are unknown. An ongoing 

national surveillance program has not been in place 

to clearly indicate whether the 12 POPs under the 

Stockholm Convention are increasing, stable, or 

decreasing. There is an indication that in other 

Arctic nations some forms of PCBs are declining, 

whereas no trends are apparent for the more chlorinated forms (Hung et al., 2001). 

Ongoing POPs Research in Alaska 

Human health and ecological research on POPs 

levels and effects in Alaska is increasing, linking the 

domestic and transpolar efforts of the Arctic Monitoring and Assessment Program (AMAP), Arctic 

Council, U.S. federal agencies, Alaska state gov5-18

Alaska—At Risk 

ernment, and tribal groups. These research efforts 

cover a spectrum from expanding work on environmental levels through measurements of body burdens and effects along the food chain to wildlife 

and humans. Emphasis is placed on community 

involvement in the planning, decision making, and 

communication of this work. Among these research efforts, measurements are underway of 

POPs levels transported in the air to Alaska and of 

levels in water and sediments of the Yukon River. 

Studies have been conducted on POPs levels in a 

wide range of species including chinook and chum 

salmon, Stellers eiders, black-capped chickadees, 

red-throated loons, and wood frogs. This research 

is accompanied by expansion of data collection on 

marine mammals and other high-trophic predators, 

notably bald eagles and polar bears. With Alaska 

Natives, traditional food practices are being documented and analyzed to assess not only the contaminant loads but also the nutritional benefits of 

the diet. POPs levels in mothers and the umbilical 

cord blood of their offspring are being measured to 

assess the body burden of contaminants. These 

data serve as an essential link in studies of potential 

effects (e.g., developmental, immunological) on the 

children. Research data have also been published 

as part of ongoing studies assessing the link between POPs levels and breast cancer (Rubin et al., 

1997) and on the effect of HCB and DDE in human cell cultures (Simonetti et al., 2001). 

These research efforts in Alaska parallel the POPs 

reduction and elimination activities under the 

Stockholm Convention. While the current Alaskan 

data outlined in this chapter serve to inform U.S. 

consideration of the Stockholm Convention, the 

ongoing work will further help to: 

❊ Monitor increases or declines in POPs levels in 

Alaska 

❊ Detect any wildlife or human hotspots of POPs 

contamination 

❊ Identify potential domestic and international 

sources of ongoing POPs contamination 

❊ Guide communities on the risks and benefits of 

traditional practices 

❊ Increase the general scientific knowledge of the 

effects of these toxic substances and the levels at 

which these effects occur. 

Conclusion 

POPs can now be measured in all environmental 

media and species in Alaska. POPs levels in Alaska 

are generally low, however, when compared to the 

lower 48 United States. Accompanying these 

comparatively low levels are isolated examples of 

elevations that portend a cautionary warning in the 

absence of international action. DDT/DDE and 

PCB levels in transient Alaskan killer whales are as 

high as those found in highly contaminated east 

coast dolphins, reaching to the hundreds of parts 

per million in lipid. On Kiska Island in the Aleutians, DDE concentrations in bald eagle eggs approach effect levels seen in the Great Lakes. And 

Aleuts have some of the highest average DDE and 

chlordane levels measured in Arctic human populations, highlighting their proximity to continuing 

emission sources in Asia. Indeed, Alaska’s location—geopolitically and climatically—suggests that 

POPs pollution could be exacerbated in future 

years in the absence of international controls. 

The hunting and dietary practices essential to survival in the Arctic make indigenous humans and 

wildlife especially vulnerable to POPs. Where 

animal fat is the currency of life, this intensifies the 

unique combination of POPs properties to migrate 

north, associate with fat, persist, bioaccumulate, 

and biomagnify. For Alaska Natives, current POPs 

levels vary with location and diet. In the human 

populations measured (Aleutian, Pribilof, North 

Slope), POPs levels are similar to those experienced by the background U.S. population, and 

generally below those of fisher communities around 

the Great Lakes. It is, therefore, important to 

emphasize that there are no known POPs levels at 

this time in Alaska that should cause anyone to 

stop consuming locally obtained, traditional foods 

or to stop breastfeeding their children. Current 

information indicates that the risks associated with 

a subsistence diet in Alaska are low, whereas in 

contrast the benefits of this diet and breastfeeding 

children are well documented (Ebbesson et al., 

5-19

Alaska—At Risk


1996; Jensen and Nobmann, 1994; Nobmann et 

al., 1992; Scott and Heller, 1968; Bulkow et al., 

2002). Further investigation and assessment are 

needed for specific species and foods in traditional 

diets, and to broaden the database across Alaskan 

communities. The international AMAP (1998) 

report came to the same conclusion for the entire 

Arctic, and Alaskan levels of most of the POPs are 

generally lower than for other polar nations. The 

international community has also moved to further 

reduce POPs contamination through negotiation of 

the Stockholm Convention on POPs, implementation of which should help minimize future increases 

in levels of the listed POPs. 

We are as one with our ancestors and 

children. 

We are as one with the land and animals. 

[Alaska Native anthropologist Rosita Worl] 

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5-24

Introduction 

The accumulation and effects of persistent organic 

pollutants (POPs) in marine ecosystems testify to 

the magnitude and global scale of these pollutants. 

On the coasts of the continental United States, 

POPs concentrations in some marine mammals 

reach very high levels, such as in the bottlenose 

dolphins familiar off the Atlantic coast. In remote 

regions in the middle of the North Pacific Ocean, 

thousands of miles from industrial centers, albatross 

have been found to have high PCB and dioxin 

levels that may be interfering with their reproductive success. And POPs are now measured, albeit 

at much lower levels, in remote reaches of the 

Southern Hemisphere and Antarctic. Although 

these oceanic ecosystems often fall under no national jurisdiction, they are valuable economic and 

esthetic resources for all. The species that inhabit 

these areas recognize no national boundaries, nor 

do the contaminants to which they are exposed. 

As with the Great Lakes, past assumptions of the 

limitless potential of these vast water bodies to 

absorb chemicals are thwarted by the persistent and 

bioaccumulative nature of these contaminants, 

focusing and maintaining their presence in biological food chains amidst the vast oceanic distances. 

The very high levels of POPs found in some marine 

mammals, e.g., dolphins, killer whales, and beluga 

whales, inevitably lead to questions about their links 

to mass strandings and mortality events. The popular scientific literature contains many stories, articles, and opinions suggesting that the concentrations of POPs accumulated by various marine 

mammal species are sufficient to be causing adverse 

effects. However, these exposure data are not 

backed by the rigorous toxicological information 

necessary to allow a sound estimate of the actual 

impacts of these contaminants. Resolution of these 

questions, necessary because POPs levels are inAccumulation and Effects of 

Persistent Organic Pollutants in 

Marine Ecosystems and Wildlife Chapter 6 

deed troubling, is difficult because modern society 

treats these highly intelligent and social creatures 

with great deference, formalized through the Marine Mammal Protection Act. 

very difficult to obtain permission to experimentally 

dose marine mammals with contaminants. 

human epidemiology, it is difficult to isolate causal 

agents in the presence of viral and bacterial infective illness, natural toxins (e.g., red tides), food 

shortages, predation, and the soup of chemical 

contaminants and exposures. 

This chapter examines POPs in the marine environment: their transport and the resulting levels, 

trends, and distributions. 

adverse effects on the species most at risk from 

POPs—those at the top of the food chain accumulating the greatest concentrations of contaminants. 

Field observations of ocean birds, inshore and 

offshore, are summarized, demonstrating adverse 

reproductive effects both historically and recently. 

Research data are then provided summarizing the 

evidence for adverse effects on marine mammals. 

Transport of POPs and the Role of 

Oceans as Sinks 

POPs have spread over the entire surface of the 

Earth, as evidenced by their occurrence in the air, 

water, and wildlife of the open oceans. 

teristics of POPs that favor their long-range transport are semivolatility, persistence in the atmosphere, and high chemical and biological stability 

(see Chapters 7, 9). 

runoff and rivers. 

late in marine sediments, particularly in estuaries 

and other near-shore areas. 

these sediments represent an ongoing source of 

contaminants that can be recirculated into the food 

chain and accumulated by top predators. 

pheric transport is also of considerable importance 

As with humans, it is 

As with 

Examples are provided of 

The characPOPs are transported by 

They are deposited and accumuThe POPs present in 

Atmos6-1

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife


to near-shore marine environments where, despite 

the influence of terrestrial runoff, short-range transport of contaminated particles may represent a 

significant contribution to the total input. 

Available information demonstrates that the 

oceans, including deep ocean waters, also function 

as a major and ultimate sink for POPs (Ballschmiter, 

1992; Preston, 1992; Loganathan and Kannan, 

1991; 1994; Tanabe et al., 1994; Wania and 

Mackay, 1999; Macdonald et al., 2000; Froescheis 

et al., 2000). In the late 1970s, the U.S. Environmental Studies Board (1979) estimated that about 

50% to 80% of the total PCB residues in the U.S. 

environment were present in North Atlantic waters. 

It has also been estimated that over 60% of the 

world’s environmental PCB load is present in openocean waters (Tanabe, 1988). 

Status and Trends of POPs in North 

American Marine Ecosystems 

Analysis of time trends in environmental concentrations is necessary for understanding and managing 

the causes and effects of POPs contamination in 

marine ecosystems. On the simplest level, time 

trend studies indicate the persistence of a substance 

by simply watching its rate of decrease with time. 

On a more complex level, historical trend studies 

can be used to predict future toxic impacts or indicate times when such impacts are no longer significant. 

Time-trend monitoring programs for POPs exist in 

several countries. The International Mussel Watch 

Program and the National Status and Trends Program of the United States National Oceanic and 

Atmospheric Administration (NOAA) are examples 

(O’Connor, 1996). Temporal trend studies of 

POPs in biota (fish and oysters) from inshore/ 

coastal aquatic ecosystems have shown clear declines in tissue concentrations following bans on the 

use of POPs. Although the concentrations of POPs 

in marine biota are generally declining, the rates of 

decline are slow (Loganathan and Kannan, 1991, 

1994). This slowness results from the long residence time of POPs in the marine environment and 

cycling from sediments and other sources of contamination. 

To assess the current status and long-term trends of 

POPs in U.S. coastal marine environments, 

NOAA’s Status and Trend Mussel Watch Program 

has been monitoring the coastal waters since 

1986 (http://ccma.nos.noaa.gov/NSandT/ 

New_NSandT.html). Concentrations of POPs have 

generally declined in mussels from 154 sites along 

the U.S. coast, although some local trends remain 

uncertain (O’Connor, 1996, 1998) (Figures 6-1, 6-

2). For fish, the National Benthic Surveillance 

Project, a component of NOAA’s Status and 

Trends Program, has monitored levels from the 

West Coast of the United States since 1984 and 

found no consistent trend in POPs concentrations 

(Brown et al., 1998). These studies have also 

documented that fish, mussels, and sediment collected near urbanized coastal areas continue to 

contain relatively high concentrations of POPs 

(Daskalakis and O’Connor, 1995; O’Connor, 

1996; Brown et al., 1998). 

Although the concentrations of POPs in sediment 

and oysters from coastal areas have declined following use restrictions, concentrations in marine mammals have declined only slightly over the past few 

decades. Very few studies have examined temporal 

trends of POPs using marine mammal tissues. No 

significant differences in concentrations of PCBs 

and DDT were observed in striped dolphins colFigure 6-1. Decreasing national median concentrations of 

contaminants in mussels. Sum values; PCB value divided 

by 10. 

Source: NOAA (nanogram/g dry weight) 

6-2

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife 

Figure 6-2. Time trends of PCBs in Alaskan mussels. 

Source: NOAA, http://ccma.nos.noaa.gov/NSandT/AKtPCB.html 

lected from the western North Pacific Ocean between 1978–79 and 1986 (Loganathan et al., 

1990) (Figure 6-3). Similarly, fur seals collected 

from the northern North Pacific Ocean showed no 

decline in concentrations of PCBs during the 1980s 

(Tanabe et al., 1994). Six- to ten-year trends in the 

concentrations of POPs in the Canadian Arctic 

have been examined in female ringed seals and 

male narwhal and beluga whales. Concentrations 

of DDTs, PCBs, chlordanes, and toxaphene 

showed no significant decline in these marine mammals (Muir et al., 1999). In fact, concentrations of 

PCBs have increased in minke whales from the 

Antarctic since 1984, and the other POPs have 

remained at a steady state (Aono et al., 1997). 

Figure 6-3. POPs concentrations in North Pacific dolphins 

(Loganathan et al., 1990). 

Similarly, concentrations of PCBs and chlordanes 

in minke whales collected from the North Pacific 

Ocean in 1994 were higher than those collected in 

1987 (Aono et al., 1997). The current absence of 

a reduction in the residue levels of POPs in marine 

mammals is consistent with an ongoing redistribution of POPs up the food chain into long-lived 

animals, and emphasizes the long-term potential 

toxic impacts of POPs. 

Routes of Exposure of Marine 

Mammals and Seabirds to POPs 

POPs reach marine environments by atmospheric 

deposition or in terrestrial runoff from rivers. Because of their relatively low water solubilities, POPs 

tend to be strongly bound to particulate matter in 

sediments in aquatic ecosystems. Invertebrate 

animals living in sediments, such as worms and 

shellfish, eat the POPs bound to food particles and 

also receive some uptake of POPs directly from 

water. Fish and other predators consume these 

invertebrates and accumulate a variety of organic 

contaminants. POPs biomagnify at each subsequent step up the food chain (i.e., reach higher 

concentrations in the predator than in its food). In 

marine ecosystems, many of these top predators 

are birds or marine mammals. A study from the 

western North Pacific Ocean has shown the concentrations of PCBs and DDTs in striped dolphins 

to be 10 million times greater than in surface waters (Tanabe et al., 1984) (Table 6-1). Although the 

concentrations in water or prey items were low, 

marine mammals have large pools of fatty tissues, 

long lifespan and reduced capacity to metabolize 

POPs. As a result, they accumulate high concentrations of POPs in their tissues (Tanabe et al., 

1994). 

Table 6-1. s biomagnify in the North 

Pacific Ocean from surface waters through 

plankton to marine mammals (Tanabe et al., 1984) 

Concentration (pg/g) PCBs DDTs 

Surface water 0.28 0.14 

Zooplankton 1800 1700 

Myctophids 48000 43000 

Squid 68000 22000 

Striped dolphin 3700000 5200000 

PCBs and DDT

6-3

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife


Concentrations in squid in the North Pacific provide further evidence of the link between environmental pollution and subsequent contamination 

high on the food chain in marine mammals and 

birds. Hashimoto et al. (1998) measured polychlorinated dioxin and furan levels in predatory squid in 

a transect of the North Pacific from Japan to near 

the coasts of Canada and the United States, with 

additional samples from New Zealand waters (Figure 6-4). Squid taken from waters near industrial 

centers, such as Japan, showed considerably higher 

levels of dioxins and furans. The lowest levels were 

found in the far South Pacific. The levels of dioxins 

and furans in these abundant and relatively shortlived (1–2 years) predator/prey animals in the 

remote North Pacific Ocean provide a clear marker 

of the level, extent, and contemporary nature of 

POPs contamination. This contamination of the 

North Pacific offers potential insights when considering the sources of elevated POPs levels in albatross on Midway Atoll (see below). 

Further POPs transfers can still occur once contaminants have reached adult predators at the top 

of food chains. POPs are passed on to the next 

generation by transfer into the eggs of birds, and 

they are passed either directly or via milk into the 

progeny of marine mammals. Such transfers of 

relatively high concentrations of POPs to the developing young raise serious questions about the potential effects of these compounds on wildlife populations. 

Adverse Effects on Wildlife 

The global distribution of POPs has been well documented (Tanabe et al., 1983; Iwata et al., 1993; 

Zell and Ballschmiter, 1980). The adverse effects 

of POPs on test animals have also been demonstrated in many studies in laboratories and in the 

field. It is the challenge of ecotoxicology to identify 

and/or predict the possibility of adverse effects in 

wildlife populations based on the known chemical 

distributions and known toxic effects. In many 

Figure 6-4. Polychlorinated dioxin and furan levels in North Pacific squid (pg/g squid liver) 

(Hashimoto et al., 1998). 

6-4

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife 

cases where discrete chemical applications occur 

and adverse effects are clearly evident, such as 

acute lethality (e.g., fish kills), it is easy to link the 

chemical exposure to the adverse effect. However, 

in the case of POPs, many of the adverse effects 

are chronic and subtle, and evaluating their relevance to population level effects is difficult. Wildlife are also more commonly exposed to relatively 

low environmental concentrations of POPs, and 

these exposures accumulate over long time periods—whole lifetimes for most animals. Finally, 

although most POPs are generally metabolized 

slowly, if at all, there are differences in uptake and 

elimination that lead to differences in the patterns 

of compounds accumulated in different species. 

These dissimilarities can result in different contaminant exposures to different animals living in the 

same environment. In the following sections of this 

report, we provide information on the exposures 

and effects of POPs on different classes of marine 

species. 

Inshore Birds 

The effects of POPs on a number of bird species 

have been demonstrated in laboratory and field 

studies (Beyer et al., 1996; Blus, 1996; Wiemeyer, 

1996). At high concentrations, many POPs can be 

acutely toxic. This toxicity is particularly pronounced in pesticides, such as dieldrin, which are 

neurotoxins. However, of more concern at current, 

relatively low environmental concentrations are the 

chronic effects of a number of POPs on the reproductive success of birds. PCBs and dioxins have 

been shown to adversely affect the reproductive 

success of fish-eating water birds in the Great Lakes 

(see Chapter 3). A more historically significant 

effect was the near extinction of some bird species 

resulting from the adverse effects of DDT residues. 

Pelicans (Pelicanus occidentalis) in the Gulf of 

Mexico were particularly affected by DDT and its 

residues (Figure 6-5). These compounds accumulated in the adult birds and caused the production of 

abnormally thin eggshells (Figure 6-6). During 

incubation in the nest, these thin shells were easily 

broken by the relatively clumsy adults. The result 

was severe depopulation in this and other species 

around the Gulf of Mexico and in other parts of the 

Figure 6-5. DDT use led to severe impacts on brown 

pelicans in the Gulf of Mexico. 

Photo: NOAA 

United States. On the Pacific coast, daily discharges into the Los Angeles sewer system contained hundreds of pounds of DDT in the 1960s. 

This DDT was eventually discharged to the Pacific 

Ocean. Coastal waters became contaminated, and 

brown pelicans nesting on Anacapa Island more 

than 60 miles away suffered near-complete nesting 

failure. The colony was littered with broken eggs, 

with eggshells averaging 31% (for intact eggs) to 

Figure 6-6. fect of DDE on eggshell thickness in 

pelicans from North America (data from Blus, 1996). 

Ef

6-5

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife


50% (broken eggs) thinner than normal. In 1969, 

1,125 pairs of pelicans were able to fledge only 4 

young birds, and in 1970, 727 pairs produced 5 

chicks (Anderson et al., 1975). 

By the end of 1970, the DDT discharge had been 

stopped, leading to a remarkable recovery in reproductive success (Anderson et al., 1975). By 1974, 

DDT residues in anchovies, the primary food of the 

pelicans, had declined by 97%—from 4.3 ppm to 

0.15 ppm. Contamination of pelican eggs by DDT 

residues had declined 89%. Eggshell thickness also 

improved to 16% (intact eggs) and 34% (broken 

eggs) thinner than normal, indicating that by 1974 

the abnormal shell thinning caused by DDT and 

DDE had been reduced by nearly half. Eggshell 

thinning up to about 10% can be tolerated without 

affecting reproduction at the population or colony 

level. The improvement in reproductive success 

was spectacular. In 1974, 1,286 pairs of pelicans 

fledged 1,185 young birds. In terms of the number 

of young birds raised per nest, the figure rose from 

a low of 0.004 in 1969 to 0.922 in 1974—an 

improvement in reproductive success of more than 

200-fold. These figures confirm the severity of 

DDT’s effect on the reproduction of carnivorous 

birds, and exemplify the remarkable improvement 

possible when the release of DDT into the local 

environment is stopped. 

of the “dirty dozen” POPs (Table 6-2). In most 

cases, the absence of a particular POP in one of 

these species is because it has not been looked for, 

not because the POP is not present. 

The degree of concern regarding POPs contaminants in birds has led to the use of DDE, PCBs, and 

dioxin concentrations in double-crested cormorant 

eggs as a “National Environmental Indicator” in 

Canada. Although many of these initial monitoring 

programs focused on the Great Lakes, their use as 

indicators has been extended to coastal and maritime regions. Concentrations of POPs have declined in maritime regions since their peaks in the 

1970s and 1980s, but the rate of decline has 

slowed in recent years (Figure 6-7). As concentrations in the environment have decreased, so have 

the adverse effects attributable to these compounds. 

The decreases in adverse effects are demonstrated 

by the recovery of many inshore bird populations 

since their historic lows. 

Much of the contaminant decline in inshore-living 

bird species can be attributed to the large decrease 

in inputs to near-shore environments resulting from 

the banning, deregistration, and emission reductions for all of the POPs in North America. However, now that these chemicals are no longer intentionally produced and 

released in the United 

Although the principal 

Figure 6-7. ed) and DDE (yellow) concentrations in 

Canadian coastal birds (double-crested cormorant eggs) 

have declined since their peaks in the 1960s and 1970s. 

Monitoring sites in the Straits of Georgia (diamonds) 

[British Columbia], Bay of Fundy (triangles), and St. 

Lawrence estuary (squares). om Environment 

Canada: www.ec.gc.ca/ind/English/Toxic/default.cfm. 

PCB (r

Data fr

States, we cannot expect 

chemical of concern to to see a continuation of 

aquatic birds has been the dramatic decreases 

DDT, other organochlo- of the past. Future 

rines are usually mea- declines in near-shore 

sured at the same time. environments will be 

In North America, much slower and will result 

of the data collected from the global redistrihave been compiled by bution of the contamithe U.S. Geological nants currently present. 

Survey and are available Whether ultimately seelectronically (http:// questered to the deep 

www.pwrc.usgs.gov/ ocean and sediments, or 

bioeco/). The distribu- transferred to open 

tion of POPs in marine waters and accumulated 

ecosystems is such that in animals, this process 

bird samples analyzed can be expected to 

contain most, if not all, continue for a long time 

6-6

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife 

Table 6-2. ds 

POPs Pelican Cormorant Gull Eagle Albatross 

Aldrina z

Chlordane z z z

DDTb z z z z

Dieldrin z z z z

Dioxins z z z

Endrin z z

Heptachlor z z z z

HCB z z

Mirex z z z

PCBs z z z z

Toxaphene z z

Note: (http://www.pwrc.usgs.gov/bioeco/); Great Lakes data NOT included. a

In birds, aldrin is rapidly converted to dieldrin. 

b

“DDT” includes DDT and residues (e.g., DDE). 

POPs detected in North American coastal bir

z

z

z

z

z

z

z

z

z

z

Data from USGS 

(Loganathan and Kannan, 1994). Furthermore, 

although production and use of POPs such as DDT 

has ceased in North America, it continues in other 

regions through limited exemptions available under 

the Stockholm Convention and in nonsignatory 

countries. 

Offshore Birds 

Recent studies of offshore-living birds have highlighted the presence of relatively high concentrations of POPs in remote ocean environments 

(Jones et al., 1996; Auman et al., 1997). Several 

studies have focused on albatross colonies on Midway Atoll in the North 

American Great Lakes (Figure 6-10). POPs concentrations in one albatross species were sufficient 

to suggest a significant risk to the reproductive 

success of the population. 

Populations of albatross species in the North Pacific 

are presently on the increase following the cessation of hunting, which in the early 1900s almost 

drove the birds to extinction (McDermond and 

Morgan, 1993). Nonbreeding Laysan albatross 

(Diomedea immutabilis) mainly frequent the western Pacific and Asian coasts, while black-footed 

albatross (D. nigripes) are more common along the 

northeastern Pacific and 

Pacific Ocean (Figure 6-

Figure 6-8. Birds on remote Midway atoll in the north 

Pacific are exposed to POPs. 

Photo: NASA 

North American coasts. 

8). The atoll, a former Thus, albatross are useful 

U.S. air base, is located indicators of different 

2,800 miles west of San sources of marine polluFrancisco and 2,200 tion in the North Pacific 

miles east of Japan (see Ocean. Studies on 

Figure 6-9). It is situated similar species in the 

close to the northwest- South Pacific also proern end of the Hawaiian vide useful information 

archipelago. These on the global distribution 

studies demonstrate that, of POPs in these species 

despite living in remote (Jones, 1999). Relaparts of the North Pacific tively high concentraOcean, albatross accu- tions of chlorinated 

mulate concentrations of aromatic compounds, 

POPs similar to those including PCBs and their 

observed in the North hydroxylated and methyl 

6-7

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife


Figure 6-9. 

the North Pacific Ocean at the end of the Hawaiian chain. 

Source: UNEP World Conservation Monitoring Centre 

Midway Atoll is located in the very center of 

sulfone metabolites (Klasson-Wehler et al., 1998), 

polychlorinated dibenzo-p-dioxins and 

dibenzofurans (PCDD/Fs), and non-ortho-substituted PCBs were found in fat samples from the 

North Pacific populations (Jones et al., 1996). 

Lower concentrations were measured in the South 

Pacific species (Jones, 1999). Ortho-substituted 

PCBs and DDT-related compounds were also reported in plasma samples from these populations, 

as were a range of other POPs (Auman et al., 

1997). The concentrations in the black-footed 

Figure 6-10. Levels of POPs may be sufficient to decrease 

reproduction in albatross from remote Pacific islands. 

Photo: John Giesy 

albatross are reported as sufficient to cause subtle 

adverse effects on reproduction (Auman et al., 

1997; Jones et al., 1996). Although historical data 

are scarce, they indicate that the egg-crushing rates 

and hatching rates for black-footed albatross between 1962 and 1964 were comparable to those 

of Laysan albatross from 1993 to 1994. However, 

the recent rate of cracked eggs in black-footed 

albatross, which accumulate greater concentrations 

of POPs, is greater than 5%, twice the rate observed in the less contaminated Laysan albatross. 

A statistically significant difference was also found 

in the hatching rate for the black-footed albatross 

compared with the Laysan albatross (Auman et al., 

1997). 

The concentrations of some POPs measured in 

North Pacific albatross do not differ greatly from 

concentrations measured in fish-eating birds in the 

North American Great Lakes. For example, pooled 

egg samples of black-footed albatross contained 3.8 

ppm of total PCBs and 1.8 ppm of DDE, whereas 

similar samples from Laysan albatross contained 

1.0 ppm PCBs and 0.3 ppm DDE (Auman et al., 

1997). These concentrations can be compared 

with concentrations of 9.4 ppm and 6.1 ppm of 

total PCBs found in 1988 in the eggs of Great 

Lakes Caspian terns and doubled-crested cormorants, respectively (Yamashita et al., 1993). The 

finding of elevated POPs concentrations in such a 

remote location underscores the global transport of 

these chemicals and the limitations of the global 

environment to assimilate or “dilute” them to safer 

concentrations (Jones et al., 1996). 

Marine Mammals 

No situation indicates more the global nature of the 

POPs problem than the concentrations detected in 

marine mammals from around the world. Even 

though many marine mammals are not directly 

exposed to POPs sources, particularly in the oceans 

of the Southern Hemisphere, every marine mammal tissue analyzed contains at least some of the 

“dirty dozen” POPs (Colborn and Smolen, 1996). 

The life history parameters of many marine mammals result in their accumulating high concentrations of POPs. Marine mammals inhabit aquatic 

6-8

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife 

environments that are the ultimate sinks for many 

of these compounds. They have a unique lifestyle 

that requires thick layers of blubber to provide 

thermal insulation and energy reserves for fasting 

periods in their life cycles. These fatty tissues act as 

a reservoir for the accumulation of POPs, and also 

act as a continual source “resupplying” the rest of 

the body with these contaminants when fats are 

metabolized. The long lifespan and generally 

predatory feeding habits of marine mammals lead 

to high levels of POPs in blubber. In addition, 

marine mammals appear to be limited in the biochemical processes required to metabolize and 

eliminate these chemicals (Tanabe et al., 1988). 

Finally, because of the high lipid content of marine 

mammal milk, POPs are passed via lactation to the 

developing young. 

Of the compounds studied in marine mammals, 

PCBs appear to accumulate to the greatest concentrations in the widest range of species (Table 6-3) 

(Tanabe et al., 1983; 1994). Very high POPs 

levels have been measured on the U.S. East Coast 

in bottlenosed dolphins, reaching 620 and 200 

ppm lipid weight for PCB and DDE, respectively, in 

mature males (Geraci, 1989). To put these concentrations in perspective, U.S. hazardous waste regulations for PCB liquids commence at 50 ppm. 

It has been contended that, since 1968, 16 species 

of aquatic mammals have experienced population 

instability, major stranding episodes, reproductive 

impairment, endocrine and immune system disturbances, or serious infectious diseases (Colborn and 

Smolen, 1996). The authors also suggest that 

organochlorine contaminants, particularly PCBs 

and DDTs, have caused reproductive and immunological disorders in aquatic mammals (Colborn and 

Smolen, 1996). The presence of high concentrations of PCBs in tissues has also been associated 

with 

❊ High prevalence of diseases and reduced reproductive capability of the Baltic grey seal 

(Halichoerus grypus) and ringed seal (Phoca 

hispida) (Olsson et al., 1994) 

❊ Reproductive failure in the Wadden Sea harbor 

seal (Phoca vitulina) (Reijnders, 1986) and St. 

Lawrence estuary beluga whales (Delphinapterus 

leucas) (Martineau et al., 1987) 

❊ Viral infection and mass mortalities of the U.S. 

bottlenose dolphin (Tursiops truncatus) (Kuehl et 

al., 1991; Lipscomb et al., 1994), Baikal seal 

(Phoca sibirica) (Grachev et al., 1989), and 

Mediterranean striped dolphin (Stenella 

coeruleoalba) (Aguilar and Raga, 1993; Kannan 

et al., 1993) 

However, unequivocal evidence of a “cause-effect” 

linkage between disease development and mass 

mortalities in marine mammals is lacking, because 

of confounding factors that limit the ability to extrapolate results from field studies. 

Compelling evidence that marine mammals can 

experience toxic effects comes from data on the 

feeding of wild-collected fish from different regions 

to confined seals (Reijnders, 1986, 1994; Ross et 

al., 1995, 1996, 1997). In the Reijnders study, 

two matched groups of captive harbor seals were 

maintained in the same location. One group was 

fed Baltic Sea herring, the other North Atlantic 

herring. The group fed Baltic Sea fish suffered 

near-complete reproductive failure, while the group 

fed less contaminated Atlantic fish reproduced 

normally. Similar impacts were evident on immune 

function. However, although the effects of consuming contaminated fish were clear, the specific causal 

agent(s) was not. As with field studies, several 

confounding factors prevent a conclusive connection between specific substances and effects in 

these studies. These factors include limited sample 

sizes, the presence of chemicals other than POPs in 

the food fish, the presence of chemical contaminants in the “control” diet, as well as general concerns about the nutritional quality and similarity of 

the “control” and “exposed” diets. Additional toxic 

effects attributed to PCBs and DDT in seals resident 

in the Baltic Sea include uterine stenosis and occlusions in ringed seals, skull-bone lesions (osteoporosis) in Baltic gray seals and harbor seals, adrenocortical hyperplasia in Baltic ringed and gray seals, 

lowered levels of vitamin A and thyroid hormones 

in harbor seals, and lowered immunocompetence in 

harbor seals (Reijnders, 1994; Hutchinson and 

Simmonds, 1994). 

6-9

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife


Table 6-3. 

PCBs, μg g-1 

wet weight, 

Species Location blubber Reference 

Bottlenose dolphin East USA 81.4 Kuehl et al., 1991 

White-sided dolphin East USA 50.1 Kuehl et al., 1991 

Common dolphin East USA 36.5 Kuehl et al., 1991 

Pilot whale East USA 17 Varanasi et al., 1993 

Minke whales West USA 3.3 Varanasi et al., 1993 

Harbour porpoise United Kingdom 55.5 Morris et al., 1989 

Pilot whale United Kingdom 36.9 Law, 1994 

White-sided dolphin Japan 37.6 Tanabe et al., 1983 

Dall’s porpoise North Pacific 8.6 Tanabe et al., 1983 

Baird’s beaked whales Japan 3 Subramanian et al., 1988 

Bottlenose dolphin South Africa 13.8 Cockroft et al., 1989 

Dusky dolphin South of New Zealand 1.4 Tanabe et al., 1983 

Common dolphin New Zealand 0.75 –>1.0 Jones et al., 1999 

Pilot whale New Zealand 0.31 Schroder, 1998 

Global PCB distribution in marine mammal populations 

Much of the controversy over marine mammal 

levels of POPs centers on the widely publicized 

mortality episodes among bottlenose dolphins 

along the Atlantic Coast of North America. Numerous causal agents, or combinations of agents, 

have been proposed, but none proven. Apart from 

chemical contaminants, exposure to natural marine 

toxins has been hypothesized as a possible cause 

for the bottlenose dolphin mortality episodes 

(Anderson and White, 1989). However, later studies have indicated that this evidence is circumstantial (Lahvis et al., 1995). Morbillivirus infection 

appears to have been at least a contributing factor 

in the dolphin mortality (Belfroid et al., 1996). 

Lahvis et al. (1995) hypothesized that synthetic 

chemicals, specifically AhR-active POPs, render 

marine mammals more susceptible to opportunistic 

bacterial, viral, and parasitic infection. Debilitating 

viruses such as morbillivirus may result in further 

immunosuppression, starvation, and death (Lahvis 

et al., 1995). Conclusions about causality are 

further complicated by the fact that marine mammals are exposed simultaneously to a number of 

synthetic halogenated hydrocarbons, many of 

which are not quantified or identified. Despite the 

high accumulation and possible adverse effects of 

PCBs in marine mammals, tissue concentrations of 

PCBs that would affect the immune system in marine mammals have not been established. Similarly, 

factors such as population density, migratory movement, habitat disturbance, and climatological factors 

have been proposed as playing roles in mass mortalities of marine mammals. 

Probably the most convincing case for observable 

adverse effects of chemical contaminants on 

marine mammals is in beluga whales 

(Delphinapterus leucas) resident in the Gulf of 

St. Lawrence on the U.S.-Canada border (http:// 

www.medvet.umontreal.ca/services/beluga/ 

beluga_homepage.html). Whales from this population have been shown to have a high incidence of 

cancers not common in other animals (Figure 

6-11), as well as a variety of other lesions (DeGuise 

et al., 1994). It is known that these animals accumulate large concentrations of POPs, and it has 

been suggested that such accumulation may be a 

contributing factor to the observed effects. However, these animals also accumulate, or are exposed 

to, high concentrations of other environmental 

pollutants, including polycyclic aromatic hydrocarbons (PAHs). Because Ah-receptor active POPs are 

tumor promoters, POPs may be a significant contributing factor to the observed cancer occurrence 

in these animals. However, because of the limited 

amount of quantitative toxicological information 

6-10

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife 

Figure 6-11. Intestinal cancer in a beluga whale. 

Source: Daniel Martineau, University of Montreal 

available about marine mammals (as discussed 

above), the relative contribution of POPs to these 

effects may never be known. 

The above-mentioned field studies indicate an association between POPs and adverse health effects in 

marine mammals, although the association is not 

conclusive to specific chemicals. Other studies 

have focused on the in vivo and in vitro effects of 

POPs on marine mammal immune function (De 

Guise et al., 1998). These studies have shown 

some effects, but it is difficult to relate the effects 

observed to a functional deficit in the immune 

systems of free-living marine mammals. It has been 

suggested that immune suppression as the result of 

POPs exposure may be a contributing factor to 

marine mammal mass die-offs, such as occurred in 

the Mediterranean in 1992 (Aguilar and Raga, 

1993). 

Toxicological data for the effects of PCBs and 

dioxins on marine mammals were recently compiled, analyzed, and used to derive toxicity reference values (TRVs) (Table 6-4) (Kannan et al., 

2000). The TRVs express the best available estimate of the concentrations of chemicals that will 

result in adverse effects. Adverse effects can be 

increasingly anticipated if the concentration of the 

chemical in an animal’s tissue rises above the TRV. 

The TRVs were derived on the basis of the concentration of chemicals in the food that marine mamTable 6-4. oxicity reference values for marine 

mammals (lipid weight basis) 

Total PCBs 

Food based 10-150 ng/g 

Tissue based (blubber) 17,000 ng/g 

Source: Kannan et al., 2000. 

T

mals were consuming, or on the concentrations of 

these chemicals in the blubber (fat) of the animals. 

They were based on studies examining physiological effects such as vitamin A depletion, suppression 

of natural killer cell activity, and the proliferative 

response of lymphocytes to mitogens. Details 

regarding derivation of the TRVs are discussed in 

Kannan et al. (2000). Because PCBs, dioxins, and 

furans are considered to act through the same 

mechanism of action, the authors used a weighted 

sum of all the exposures to these chemicals, called 

“toxicity equivalence” or TEQ. 

Using these TRVs, it is possible to conduct a risk 

screening for the possibility of adverse effects from 

these chemicals in marine mammals. For example, 

the blubber concentrations of PCBs in pilot whales 

and bottlenose dolphins from the United States 

exceed the TRV values (Table 6-5). This suggests 

that these animals may be subject to adverse effects 

from these chemicals. In contrast to the North 

American samples, PCB concentrations in marine 

mammals in the Southern Hemisphere are far 

lower. 

Other Marine Mammals: Pinnipeds, 

Manatees, and Otters 

A wide range of POPs have been measured in the 

tissues of seals, sea lions, and walruses (collectively 

called pinnipeds) (Figure 6-12). These include 

chlordanes, heptachlor epoxide, HCB, dieldrin, 

toxaphene, PCBs, PCDDs, and PCDFs 

(Hutchinson and Simmonds, 1994; Ames and Van 

Vleet, 1996). POPs concentrations vary widely 

depending on species, location, and feeding patterns. Concentrations in species feeding at low 

trophic levels in remote locations, such as walrus in 

the Bering Straits (Figure 6-12), remain in the subppm range (Seagars and Garlich-Miller, 2001). 

6-11

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife


Table 6-5. 

Blubber PCB Blubber PCB Exceedance 

Species TRV (ng g-1) PCB (ng g-1) (Ratio PCB/TRV) 

Bottlenose (USA) 13,600 81,400 6.0 

Pilot whale (USA) 13,600 17,000 1.25 

Dall’s porpoise (Pacific) 13,600 8,600 0.63 

Pilot whale (NZ) 13,600 310 0.023 

Baleen whales (NZ) 13,600 12.9 0.0001 

NZ fur seal (NZ) 13 600 1,069 0.08 

Note: TRVs are given on a wet weight basis. 

Source: Kannan et al., 2000. 

Risk screening of PCBs in marine mammals 

Closer to sources, the relatively high concentrations 

of PCBs (85 to 700 ppm) found in harbor seal 

blubber, such as in the Wadden Sea, have been 

implicated in their mass mortalities and reproductive impairment (Reijnders, 1986). Similarly, elevated exposure of California sea lions to DDT in 

the 1970s has been linked to reproductive problems (Figure 6-13) (DeLong et al., 1973). California sea lions collected in the early 1970s from 

coastal California contained a mean DDT concentration of 980 ppm lipid weight in the blubber 

(DeLong et al., 1973). A recent study has reported 

DDT concentrations of up to 2,900 ppm lipid 

weight in the blubber of California sea lions from 

the California coast (Kajiwara et al., 2001). DDT 

concentrations as high as 169 ppm lipid weight 

were also found in the livers of sea otters from 

coastal California (Nakata et al., 1998). The occurFigure 6-12. Pinniped marine mammals, like these walrus, 

accumulate POPs to varying degrees depending on 

species, location, and feeding patterns. 

Photo: NOAA 

rence of several tens of ppm of PCBs and DDTs 

has been reported in harbor seals collected in 

1990–1992 (approximately 20 years after the ban 

on the use of DDT) from the northeastern United 

States (Lake et al., 1995). And the Florida manatee, Trichechus manatus, an endangered species, 

has been reported to contain several ppm levels of 

PCBs and DDT in blubber (Ames and Van Vleet, 

1996). 

Summary and Conclusions 

Adverse effects from POPs on marine mammals 

and birds demonstrate the potential for these substances to affect species in regions far from the 

sources of the POPs emissions. At the peak of 

DDT use in the United States, many marine bird 

species suffered eggshell thinning from DDT, most 

particularly the brown pelican which became threatFigure 6-13. DDT is believed to have caused reproductive 

problems in California sea lions in the 1970-80s. 

Photo: NOAA 

6-12

Accumulation and Effects of POPs in Marine Ecosystems and Wildlife 

ened with extinction. Impacts on birds continue in 

some locations, including elevated exposures in 

remote reaches of the Pacific Ocean. For marine 

mammals, controlled studies of high environmental 

pollutant exposures in their food have demonstrated reproductive impairment and immune 

changes. But although many marine species are 

exposed to POPs, there are few studies that 

“prove” a causal link between specific POPs at 

more general environmental levels and adverse 

effects in populations or individuals. Nevertheless, 

risk evaluations indicate cause for concern. Concentrations of POPs in some species and locations 

are currently at levels close to those with the potential to cause adverse effects. Therefore, it can no 

longer be assumed that the world’s oceans can 

dilute these chemicals to “safe” concentrations. 

As with the Great Lakes, however, there have been 

remarkable recoveries in wildlife populations with 

the cessation or reduction of POPs release. POPs 

levels in U.S. coastal regions are declining in sediments and invertebrates. Less evident are reductions in POPs levels in fish and mammal species, 

testifying to the peculiar hazard posed by these 

persistent, bioaccumulative, toxic substances and 

their ability to remain in the food chain and pass 

from generation to generation. Decreases in marine POPs levels following production and use 

controls indicate that regulatory actions can be 

successful. However, because of the problems of 

global transportation and deposition of these contaminants, the desired decreases in global POPs will 

not be achieved without global cooperation. 

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seals feeding on fish from polluted waters. Nature 

324:456-457. 

Reijnders PJH. 1994. Toxicokinetics of 

chlorobiphenyls and associated physiological responses 

in marine mammals, with particular reference to their 

potential for ecotoxicological risk assessment. Sci Total 

Environ 154:229-236. 

Ross PS, De Swart RL, Reijnders PJ, Van Loveren H, 

Vos JG, Osterhaus AD. 1995. Contaminant-related 

suppression of delayed-type hypersensitivity and antibody responses in harbor seals fed herring from the 

Baltic Sea. Environ Health Perspect. 103(2):162-7. 

Ross PS, De Swart RL, Addison R, Van Loveren H, Vos 

J, Osterhaus A. 1996. Suppression of natural killer cell 

activity in harbour seals (Phoca vitulina) fed Baltic Sea 

herring. Aquat Toxicol 34:71. 

Ross PS, de Swart RL, van der Vliet H, Willemsen L, de 

Klerk A, van Amerongen G, Groen J, Brouwer A, 

Schipholt I, Morse DC, van Loveren H, Osterhaus AD, 

Vos JG. 1997. Impaired cellular immune response in 

rats exposed perinatally to Baltic Sea herring oil or 

2,3,7,8-TCDD. Arch Toxicol. 71(9):563-74. 

Schröder C. 1998. Levels of polychlorinated biphenyls 

and life history parameters in long-finned pilot whales 

(Globicephalus melas) from New Zealand strandings. 

MSc thesis, Victoria University of Wellington, 

Wellington, New Zealand. 

Seagars DJ, Garlich-Miller J. 2001. Organochlorine 

compounds and aliphatic hydrocarbons in Pacific walrus 

blubber. Mar Pollut Bull 43(1-6):122-131. 

Subramanian A, Tanabe S, Tatsukawa R. 1988. Estimating some biological parameters of Baird’s beaked 

whales using PCBs and DDE as tracers. Mar Pollut Bull 

19:284-287. 

Tanabe S. 1988. PCB problems in the future: foresight 

from current knowledge. Environ Pollut 50:5-28. 

Tanabe S, Watanabe S, Kan H, Tatsukawa R. 1988. 

Capacity and mode of PCB metabolism in small cetaceans. Mar Mamm Sci 4:103-124. 

Tanabe S, Mori T, Tatsukawa R, Miyazaki N. 1983. 

Global pollution of marine mammals by PCBs, DDT and 

HCHs (BHCs). Chemosphere 12:1269-1275. 

Tanabe S, Tanaka H, Tatsukawa R. 1984. 

Polychlorobiphenyl, sDDT, and hexachlorocyclohexane 

isomers in the western North Pacific ecosystem. Arch 

Environ Contam Toxicol 13:731-738. 

Tanabe S, Iwata H, Tatsukawa R. 1994. Global contamination by persistent organochlorines and their 

ecotoxicological impact on marine mammals. Sci Total 

Environ 154:163-177. 

U.S. Environmental Studies Board. 1979. PCB transport throughout the environment. In: Polychlorinated 

Biphenyls. Washington, DC: National Academy of 

Sciences, pp. 146-168. 

Varanasi U, Stein JE, Tilbury KL, Brown DW, Meador 

JP, Krahn MM, Chan S-L. 1993. Contaminant monitoring for NMFS marine mammal health and stranding 

response program. Coastal Zone ‘93 (ISBN 0-87262-

918-X) pp. 2516-2530. 

Wania F, Mackay D. 1999. Global chemical fate of ahexachlorocyclohexane. 2. Use of a global distribution 

model for mass balancing, source apportionment, and 

trend prediction. Environ Toxicol Chem 18:1400-

1407. 

Wiemeyer SN. 1996. Other organochlorine pesticides 

in birds. In: Environmental Contaminants in Wildlife: 

Interpreting Tissue Concentrations. New York: Lewis 

Publishers, pp. 49-71. 

Yamashita N, Tanabe S, Ludwig JP, Kurila H, Ludwig 

ME, Tatsukawa R. 1993. Embryonic abnormalities and 

organochlorine contamination in double-crested cormorants (Phalacrocorax auritus) and Caspian terns 

(Hydroprogne caspia) from the upper Great Lakes in 

1988. Environ Poll 79:163-173. 

Zell M, Ballschmiter K. 1980. Baseline studies of global 

pollution. II. Global occurrence of hexachlorobenzene 

(HCB) and polychlorocamphenes (PCCs) in biological 

samples. Fresenius Z Anal Chem 300:387-402. 

6-16

Introduction 

Persistent organic pollutants (POPs) are now 

nearly ubiquitous in their distribution over the 

Earth. They can be found in remote locations 

distant from industrial and agricultural regions, as 

well as close to their point of introduction into the 

environment. Their propensity for long-range 

environmental transport, and the extent of their 

distribution, are evident from the levels reported for 

the Great Lakes, Alaskan Arctic, and marine ecosystems. This chapter provides information on 

how POPs are transported such long distances by 

winds, river and ocean currents, and migratory 

animals. The focus is on transport of POPs into 

the United States, recognizing that POPs also leave 

the United States and have impacts on other countries through similar processes. Particular attention 

is directed to transport in the atmosphere, because 

this is the principal medium through which POPs 

are distributed globally, either as vapor or on particles. Examples are provided of the transport of 

pollutants between continents, accompanied by an 

overview of the atmospheric chemistry of POPs 

relating to entrainment, degradation, and deposition. Methods for tracking the transport of POPs 

through the atmosphere are discussed, with examples provided of the pathways they may take. 

This discussion is followed by a summary of information on hydrologic movement and transport of 

POPs via migratory species. 

The behavior of POPs in the environment is complex because they are multimedia chemicals, existing and exchanging among different compartments 

of the environment such as the atmosphere, natural waterbodies, soil, and sediments, where they 

degrade at different rates over time. POPs are also 

referred to as semivolatile, meaning they can be 

present in more than one phase in the atmosphere, either as gases or attached to airborne 

particles. The fate and preferential transport of a 

Long-Range Environmental 

Transport of Persistent 

Organic Pollutants Chapter 7 

POP are strongly determined by its specific physical 

chemistry properties, even its particular isomer (i.e., 

same molecular formula but different spatial structure). 

ticles, water, and/or lipid molecules, and their rate 

of volatilization will determine the pathway each 

species or isomer is likely to take in its journey 

through the environment. 

influence how far and fast a POP can move from 

where it was released into the environment. 

Comprehensive monitoring studies support the 

conclusion that POPs concentrations are generally 

highest in areas where they were once released, or 

are still being released. 

decrease with increasing distance from such source 

areas. 

dependent on past and present release rates in the 

immediate vicinity under investigation, and are also 

strongly influenced by regional releases (Kalantzi et 

al., 2001). , the finding of 

surprisingly high concentrations of POPs in polar 

areas, particularly the Arctic (Bidleman et al., 

1989; Barrie et al., 1992; Iwata et al., 1993), has 

led to an emphasis on the natural processes that 

are responsible for this wide-ranging transport 

through the global environment. 

include: 

❊ Volatilization of POPs from terrestrial and/or 

aquatic surfaces into the atmosphere 

❊ Adsorption of POPs vapor onto particles already 

entrained in the atmosphere 

❊ Entrainment from a surface of particles with an 

adsorbed POPs layer into the atmosphere 

❊ Transport of air masses throughout a hemisphere by means of persistent, large-scale circulation patterns or by means of episodic rapid 

transport processes 

The different affinities of POPs for soil parThese properties also 

Concentrations generally 

Thus, concentrations are most strongly 

In addition, however

These processes 

7-1

Long-Range Environmental Transport of POPs


❊ Photochemistry and interaction of POPs with 

free radicals, which can modify and degrade 

their chemical form while they are undergoing 

atmospheric transport 

❊ Deposition by means of wet (e.g., snow, rain, 

mist) or dry (e.g., turbulent transport and particle 

settling) atmospheric processes onto terrestrial 

and aquatic surfaces of POPs that are either in 

vapor form or adsorbed onto particles 

❊ Transport of POPs in aquatic systems by means 

of flowing water (primary surface flows such as 

rivers and ocean currents) 

❊ Transport of POPs in terrestrial and aquatic 

ecosystems in the lipids of migrating mammals, 

fish, and birds 

❊ Deposition of POPs into aquatic sediments 

❊ Eventual physical accumulation in receptor locations, uptake, and bioaccumulation that increases 

concentrations in ecosystems and humans 

Atmospheric Transport of Pollutants 

to the United States 

When describing winds in the atmosphere and their 

ability to transport trace substances over long distances (e.g., the equator to the pole or around the 

globe) a convenient first approximation is to focus 

on their long-term average behavior. This focus is 

useful because winds fluctuate in strength and 

direction in passing cyclonic and anticyclonic 

weather systems, resulting in net displacements 

that are relatively small compared with the global 

scale. Average, or prevailing, winds blow much 

more in east-west directions than in north-south 

directions. In midlatitudes, the prevailing winds are 

westerly (i.e., from the west), whereas easterly 

winds prevail at very high latitudes and in the subtropics (e.g., southern Florida), the latter especially 

in spring and summer. In principle, pollutants 

released at the surface can travel eastward completely around the globe at midlatitudes in about 10 

days if they are lifted by convective activity (strong 

upward air motions that produce clouds) to the 

altitude of the jet stream. The average wind speeds 

at this level are much stronger than they are near 

the surface and can exceed 100 mph in the core of 

the jet stream (e.g., Stull, 2000), and the wind 

speeds and directions are more constant than they 

are near the surface. In contrast to this rapid westeast transport in the jet stream, it takes several 

months for pollutants to spread from equator to 

pole. It can take even longer, about a year to a 

year and a half, for pollutants to cross the equator 

and be evenly distributed over the globe (Warneck, 

1988). Mixing caused by small-scale turbulence 

normally causes pollutants to disperse so they no 

longer form a coherent plume that can be tracked 

over long distances. However, on occasion, 

plumes of airborne substances remain coherent 

and can be tracked for long distances. 

Much of the evidence for long-range transport of 

airborne gaseous and particulate substances to the 

Figure 7-1. Atmospheric transport of Saharan dust to the 

United States. 

Source: National Aeronautics and Space Administration, 2001. 

7-2

Long-Range Environmental Transport of POPs 

United States focuses on dust or smoke because 

these are visible in satellite images or when deposited. Examples include transport of dust from the 

Sahel and Sahara Desert in northern Africa, dust 

from the Taklamakan and Gobi Deserts in Asia, and 

emissions from uncontrolled wildfires in Central 

America and southern Mexico. Windblown dust 

from individual dust storms in the Sahara Desert has 

been observed in satellite images as plumes crossing 

the Atlantic Ocean and reaching the southeast coast 

of the United States. These storms can last for 

several days at a time. A false color satellite image 

obtained by NASA’s Earth Probe TOMS satellite 

showing successive pulses of Saharan dust propagating eastward across the Atlantic Ocean and reaching 

Miami is presented in the top portion of Figure 7-1. 

The bottom portion of Figure 7-1 shows a true color 

image of the dust cloud over Florida obtained by 

NASA’s Sea Star satellite on the same day. Analysis 

of data obtained by the IMPROVE (Interagency 

Monitoring of Protected Visual Environments) network indicates that incursions of Saharan dust into 

the continental United States have occurred, on 

average, about three times per year. These events 

have persisted for about 10 days, principally during 

the summer. As might be expected, the frequency 

of Saharan dust events is highest in the southeastern 

United States. About half are observed only within 

the State of Florida, and these are associated with 

dense hazes in Miami (see Figure 7-2) such that 

African dust is the dominant aerosol constituent in 

southern Florida during the summer (Prospero, 

1999a). Puerto Rico and the Virgin Islands are 

even more strongly affected, as might be expected. 

Figure 7-3 shows a false color satellite image of the 

passage of a cloud of dust across the Pacific Ocean 

to North America. This dust cloud was raised by a 

storm in the Gobi and Taklamakan Deserts in April 

2001. The highest concentrations of Asian dust 

can be seen over the Aleutian Islands. Also shown 

in Figure 7-3 is a dust cloud from northern Africa 

traveling eastward over the Atlantic Ocean. 

Biomass burning for agricultural purposes occurs 

normally during the spring of each year in Central 

America and southern Mexico. During the spring 

of 1998, fires burned uncontrollably because of 

abnormally hot and dry conditions associated with 

Figure 7-2. onology impacting 

Miami, FL. 

Source: Prospero, 1999a. 

Saharan dust episode chr

the intense El Niño conditions in 1997–1998. 

Figure 7-4 shows the extent of the spread of the 

particles emitted by the fires. Concentrations of 

particles throughout the central and southeastern 

United States were elevated substantially, such that 

National Ambient Air Quality Standards for particulate matter were exceeded briefly in St. Louis, MO, 

and in a number of other cities in the central 

United States. The reader should bear in mind that 

the atmospheric processes that transport dust or 

smoke, as given in the examples above, are also 

transporting pollutants, including POPs, either as 

vapor or attached to particles. Indeed, microorganisms including various fungi and bacteria have 

been found attached to North African dust particles 

Figure 7-3. Asian dust storm episode crossing the Pacific 

Ocean. NASA. 

7-3

Long-Range Environmental Transport of POPs


Figure 7-4. Smoke from Central American fires. NASA. 

in Caribbean air samples (Griffin et al., 2001). 

Pollutants, including trace metals that may have 

been emitted in North Africa or Europe, have been 

found along with North African dust particles in 

Miami, FL (Prospero, 1999b). 

Rapid transport of pollutants from south to north 

can also occur, bringing pollutants from midlatitudes to the Arctic in a few days. Many of these 

pollutants are relatively short-lived with respect to 

degradation in the atmosphere, and are unlikely to 

reach the Arctic by the average winds described 

above. These transport events occur during winter 

and are caused by transient weather events that 

result in strong winds directed toward the north in 

a narrow current lying typically between a strong 

high-pressure region to the east and a low-pressure 

system to the west. These weather situations occur 

mainly in the former Soviet Union, although they 

can also occur in North America. These events 

result in the formation of Arctic haze, which regularly affects air quality in Alaska (Shaw and Khalil, 

1989). 

Although these episodes are infrequent, the 

amount of POPs deposited can be substantial, 

given the otherwise pristine nature of some of the 

receptor locations. For example, Welch et al. 

(1991) documented a long-range transport event 

that deposited thousands of tonnes of Asian dust 

onto a region of the central Canadian Arctic over a 

brief (<3-day) period. Analysis of the resulting 

brown snow revealed elevated levels of the following POPs: PCBs (6.9 ng/g particles), DDT 

(4.2 ng/g), toxaphene (3.0 ng/g), HCB (0.7 ng/g), 

chlordane (0.6 ng/g), heptachlor, and dieldrin, 

along with other organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and hexachlorocyclohexanes (e.g., lindane). The authors 

estimated that this single episode may have contributed up to 10% of the annual loading of DDT to 

lakes in this region, and up to 1%–3% for the other 

measured POPs (depending on loading scenario 

assumptions). 

Atmospheric Chemistry of POPs 

Many POPs, including pesticides and PCBs, are 

classified as semivolatile, meaning that they can 

exist either as gases or attached to particles. The 

relative amounts in the gaseous and particle-associated forms depend on air temperature. Less volatile POPs tend to partition into surface reservoirs 

such as soil, vegetation, rivers, and oceans, where 

they associate with organic matter. Warmer temperatures favor their evaporation and residence in 

the atmosphere as gases; colder temperatures favor 

their deposition to the Earth’s surface and their 

incorporation into airborne particles. Generally, 

warmer temperatures are found close to the Earth’s 

surface with decreasing latitude (tropics), whereas 

colder temperatures are found with increasing 

latitude (polar) or altitude. Characteristic temperatures at which half of a particular compound (T1⁄2 ) 

would be present as a gas can be calculated to 

indicate the tendency of a POP to remain as a gas 

or to attach to a particle (Wania et al., 1998). The 

more volatile POPs, such as hexachlorobenzene 

(HCB), reach this temperature at –36°C; dieldrin at 

–11°C; DDE –2°C; DDD +7°C; DDT +13°C; and 

PCBs with at least 6 Cl atoms at about +10°C. As 

the number of Cl atoms increases in PCBs, polychlorinated dibenzo-p-dioxins (PCDDs) and furans 

(PCDFs), this characteristic temperature also increases, such that molecules with more than 5 Cl 

atoms tend to be partitioned mainly onto particles 

(Brubaker and Hites, 1998). Compounds such as 

mirex and toxaphene (higher molecular weight 

fraction of the mixture) are expected to be found 

mainly attached to particles, because they have very 

7-4

Long-Range Environmental Transport of POPs 

high values of T1⁄2. Observations show that compounds with the lowest T1⁄2 tend to have the highest 

potential for global scale transport and to remain in 

the gas phase even at high latitudes, whereas compounds with the highest values of T1⁄2 tend to remain concentrated close to their sources. 

Although the meteorological processes transporting 

gases and particles are the same, particles and 

gases are subject to different removal processes 

that affect the time they remain airborne. Soluble 

gases can be removed from the lower atmosphere 

by being incorporated into cloud droplets that then 

fall out as rain, or by being washed out by falling 

raindrops. This limits their lifetime in the atmosphere typically to several days, and also limits the 

distances they can travel from their sources. However, gas-phase POPs are not very soluble and so 

their removal by precipitation is not effective. For 

example, the removal time for chlordane, dieldrin, 

and PCBs can be up to several years by this 

mechanism (Atlas and Giam, 1981). 

POPs present as atmospheric gases can be destroyed by atmospheric photochemical reactions 

involving hydroxyl (OH) radicals in the atmosphere. 

Reactions involving other species or photodegradation by solar ultraviolet radiation are considered to be minor loss processes, although data are 

sparse. Calculated atmospheric half lives, t1⁄2 (defined as the time it takes to reduce their concentrations by one-half due to reaction with OH radicals), 

for several compounds are shown in Table 7-1, 

along with their concentrations in both the gas and 

particle phases observed on the shores of the Great 

Lakes. As can be seen, t1⁄2 in the atmosphere 

ranges from a couple of days for DDT to a couple 

of years for HCB. Notably, the presence of hydroxyl radicals is integrally linked to the presence 

and level of sunlight. The absence of sunlight in 

polar regions for many months of the year effectively eliminates the generation of hydroxyl radicals, 

thereby greatly increasing the persistence of atmospheric pollutants that would otherwise be degraded 

through this mechanism during daylight. 

If POPs become attached to particles, their lifetimes 

in the atmosphere are determined by particle removal mechanisms, in addition to reactions involving hydroxyl radicals or other free radical species in 

the particles and photodegradation by solar ultraviolet radiation. However, the effectiveness of 

these processes in particles has not been studied as 

well as for the gas phase. The lifetime of particles 

in the lower atmosphere is about 1 week with 

respect to removal by precipitation. However, 

particles above cloud layers can remain airborne 

much longer and hence can be transported over 

much longer distances. Particles also can be deposited on the Earth’s surface when they are transported downward by turbulent air motions (dry 

deposition). Atmospheric lifetimes with respect to 

dry deposition depend on particle size, meteorological variables near the surface, and microphysical 

conditions at the air-surface interface. Lifetimes in 

the atmosphere for fine particles (i.e., smaller than 

a few micrometers in diameter) with respect to dry 

deposition are about a couple of weeks (U.S. EPA, 

1996). 

Deposition on to the surface does not, however, 

mean that a POP has been permanently removed 

from the atmosphere. Through a variety of mechanisms, such as microbial activity and photochemical 

reactions occurring near the surface of the soil or a 

waterbody, POPs that were attached to particles 

Table 7-1. 

POPs at IADNa sites and their estimated globally 

averaged atmospheric half-lives (t1/2) 

a Integrated Atmospheric Deposition Network. 

sites situated on each of the Great Lakes. 

b 1 pg = 1 trillionth (10-12) of a gram. c Defined here as the time needed in days to reduce the concentration of the compound by one-half, using a globally averaged OH 

concentration of 1.0 × 106

 OH/cm3 (e.g., Krol et al., 1998) and a 

mass weighted mean atmospheric temperature of 273(K (0(C). 

Source: 

Atmospheric concentrations of selected 

IADN consists of five 

Hoff et al. (1996) for concentration data. 

7-5

Long-Range Environmental Transport of POPs


may be released and evaporate into the atmosphere. Only through processes such as reaction 

with OH radicals in the atmosphere, or biologically 

mediated reactions in either soil or natural 

waterbodies, is a POP finally gone from the environment. These processes are all strongly temperature dependent and proceed faster at higher 

temperatures, so that POPs tend to persist longer 

at higher latitudes. Lifetimes of most POPs due to 

degradation in the marine or terrestrial environment are estimated to be several years, with degradation occurring more rapidly in tropical than in 

polar regions. A degradation product of the original POP may also be a POP, or may be toxic in the 

environment. For example, dieldrin is formed 

during the degradation of aldrin. 

Global Distillation of POPs 

An intriguing consequence of the combined 

semivolatile and persistent nature of POPs is their 

potential to volatilize in warm regions, be deposited 

in colder ones, and repeat this process until a 

location is reached where it is too cold for the POP 

to again revolatilize. This process is similar to 

industrial distillation processes, such as separating 

petroleum products from crude oil. On a planetary 

scale, global distillation has been hypothesized to 

result in a net transport of POPs from lower latitudes to high latitudes (polar regions) in a series of 

jumps (Wania and Mackay, 1996) (Figure 7-5). 

Because of the normal decrease of temperature 

with increasing latitude, compounds will tend to 

condense on surfaces as they are transported 

northward by winds associated with passing 

weather systems. Various thermodynamic constants can be used to estimate the "stickiness" of 

POPs to a surface. One of the most useful is the 

octanol-air partition coefficient (KOA ), which is 

measurable in the laboratory and relates to the 

tendency of a POP to adhere to organic matter in 

the soil or natural waterbodies. Values of KOA 

range over many orders of magnitude, and the 

higher its value the greater the tendency for a POP 

to associate with organic matter. 

The environmental levels of POPs predicted in 

remote locations following global distillation depend 

heavily on the physicochemical properties of the 

particular POP and the meteorological factors 

generating poleward transport. The balance between POPs concentrations in temperate regions 

versus their preferential accumulation toward the 

poles is influenced by the following factors: 

❊ Source proximity: The strength and proximity 

of emission sources act as the primary forces 

generating pollutant levels. All things being 

equal, pollutant concentrations should be greater 

at the source and taper off with distance, with 

this tapering effect proportional for all pollutants. 

But a variety of factors can differentially influence 

the transport potential of POPs and their isomers, leading to differential accumulation. 

❊ Physicochemical properties of different POPs: 

As already noted, differences among POPs regarding their propensity to exist in the vapor 

phase (e.g., KOA, Henry’s law constant, vapor 

pressure) have an impact on each POP’s susceptibility to global distillation and the rate at which 

such movement can occur. Differences occur 

even within families of POPs, such as among the 

209 PCB congeners. Lower chlorinated PCBs, 

with two or three chlorines, are more volatile and 

amenable to global transport. They tend, however, to be less persistent than the higher chlorinated PCB congeners, somewhat countering 

their propensity to preferentially move toward 

the poles. 

Figure 7-5. Grasshopper effect moving POPs poleward. 

Source: Adapted from Wania and Mackay, 1996. 

7-6

Long-Range Environmental Transport of POPs 

❊ Temperature dependence of physicochemical 

properties: Decreased temperatures and reduced microbial activity toward the poles increase POPs persistence, thereby inherently 

increasing the potential for physical accumulation (see Chapter 9). Decreased temperatures 

also alter environmental media partitioning properties, such as the water-air partition coefficient 

(Henry’s law constant), increasing the proportion 

of a chemical in water compared with the 

amount in the adjacent air column. Hexachlorocyclohexane (HCH; listed as a POP under the 

UNECE-LRTAP POPs Protocol) isomers change 

from an aquatic persistence of only a few days in 

the tropics to many months or years in Arctic 

waters. The Henry’s law constant also changes 

for the HCHs, increasing the proportion in water 

compared with air as the environment cools. 

Both of these changes contribute to the higher 

absolute levels of HCH in Arctic waters compared with those that had been found close to 

the presumed sources in Asia (Iwata et al., 

1993). 

Temperature-dependent gradients have been demonstrated on a global or regional scale for several 

of the more volatile POPs, although direct evidence 

for transfer of POPs from the tropics to the Arctic 

remains to be demonstrated (Klecka et al., 2000). 

Calamari et al. (1991) reported that HCB concentrations in vegetation increased with latitude by 

almost a factor of 10 between the tropics and polar 

regions, whereas concentrations of the less volatile 

DDT were found to be higher in tropical compared 

with polar areas by almost a factor of 100. 

Simonich and Hites (1995) reported similar results 

on the global distribution of 22 organochlorine 

compounds in tree bark samples. Here, the distribution of relatively volatile organochlorines, such as 

HCB, was dependent on latitude, whereas less 

volatile and persistent organochlorines (e.g., endosulfan) remained close to the region of release. 

Iwata et al. (1993) measured geographic gradients 

for HCH in sea water on a global scale, finding 

higher concentrations toward the poles even 

though emission sources were in temperate and 

tropical regions, predominantly Asia. Sea water 

and air concentrations of DDT were substantially 

higher near the sources measured in Asia. 

Increased altitude and the related decrease in temperature also are associated with increasing levels 

of POPs, as demonstrated over a 770 to 3,100 m 

altitude gradient in the western Canadian Rocky 

Mountains (Blais et al., 1998). Increasing snowfall 

at higher altitudes led to a 10-fold increase in deposition with height of less volatile compounds, such 

as DDT. For the more volatile organochlorines 

(e.g., lower chlorinated PCBs, HCH, and heptachlor epoxide) this increase with altitude was up 

to 100-fold, demonstrating enhancement through 

cold-condensation effects. The concentration 

gradient with altitude is particularly informative 

because it was performed in a single geographic 

location, making the study less likely to be confounded by proximity to sources, which can occur 

when there are several geographically dispersed 

measurement sites. 

Global-scale distillation effects were observed originally for the heavy isotopes (deuterium, oxygen-18) 

compared with the light isotopes (hydrogen and 

oxygen-16) of water vapor (Dansgaard, 1953). 

Light isotopes are more volatile than their heavier 

counterparts. The ratio of light to heavy isotopes 

increases with latitude, because of selective condensation of the heavier isotopes in accord with the 

Rayleigh distillation formula. For POPs, current 

field data relate to a small subset of the most volatile persistent organic substances, consistent with 

theoretical predictions (Wania and Mackay, 1996), 

i.e., hexachlorobenzene (HCB), polychlorinated 

biphenyls (PCBs), hexachlorocyclohexanes (HCH), 

and, to a lesser extent, chlordane. 

The basis of empirical support for global distillation 

comes from the differential increase in accumulation of more volatile PCB congeners (lower chlorinated) and HCH isomers (α > γ) in higher latitudes. 

Many of the factors noted above as influencing 

POPs levels in remote locations can be seen affecting, and are consistent with, these measured congener and isomer ratios. Total PCB levels were 

found to decline with increasing latitude (consistent 

with increasing distance from the source), but the 

levels of di- and trichlorobiphenyl stayed relatively 

constant with latitude (they are more volatile), 

thereby increasing as a proportion of the total PCB 

mix (Muir et al., 1996; Ockenden et al., 1998a). 

7-7

Long-Range Environmental Transport of POPs


Notable, too, is the delayed onset of PCB deposition to sediments in high Arctic lakes compared 

with midlatitude and subArctic lakes, providing 

further evidence of ongoing global distillation 

(Muir et al., 1996). Similar latitude-related ratio 

changes favoring more volatile compounds in 

northern, colder sites were reported for α-HCH 

versus γ-HCH (lindane), the former having a higher 

Henry’s law constant and vapor pressure 

(Ockenden et al., 1998b). 

Calculating and Modeling Atmospheric 

Transport of POPs 

The distribution and movement of POPs in the 

atmosphere can be calculated by computer modeling. The outputs from these models may be used 

for making predictions of future trends, for evaluating the effects of control strategies, and for improving understanding of the processes controlling the 

distribution of POPs. A complete model of the 

distribution, ultimate fate, and trends for POPs in 

the environment would include modules calculating 

the changes of emissions with time; transport by 

the atmosphere and oceans; deposition to the 

surface and volatilization from the surface; transfers 

to rain and snow; and degradation in the atmosphere, oceans, terrestrial waters, and soils. Although information and models are available for 

each of these modules for some POPs, a complete 

and validated global model has not been published, 

principally because of the complexity of the calculations and the uncertainties in input parameters. 

More pragmatically, because of their persistence, 

POPs concentrations can be directly measured in 

the animal species of interest, reducing the need 

for modeling to determine dose and risk. To date, 

POPs models have focused on either (1) bulk transfers among different media (i.e., multimedia models) or (2) simulations of atmospheric movement. 

The multimedia models currently include simplified 

treatments of transport, whereas the atmospheric 

models include highly simplified treatments of the 

transfers among the different reservoirs. These two 

modeling fields are now merging. Multimedia 

models are addressed in Chapter 9 of this report 

(see also Klecka et al., 2000). The remainder of 

this section focuses on air transport modeling. 

There are two basic approaches for calculating the 

transport of pollutants in the atmosphere. The first 

approach is to calculate trajectories, which are the 

three-dimensional paths followed by the center of 

mass of an imaginary air parcel, either forward 

from a source or backward from a receptor location. These are known as Lagrangian models. 

The second approach is based on numerical grid 

models, which include a number of physical processes such as the mixing of air parcels, chemical 

transformations, emissions, and deposition to the 

surface. These calculations are performed on 

individual boxes in a three-dimensional grid matrix, 

thereby tracking the dispersion of a pollutant 

across this grid (Eulerian models). Both approaches rely on the use of meteorological data 

obtained from ground-based measurements, 

weather balloons, and satellites. In some cases, 

global climatological model simulations are used 

rather than real observations. 

Both approaches have advantages and limitations. 

The first, or trajectory, approach has the advantage 

of simplicity, although it minimizes the physical 

processes mentioned above. For example, after a 

short time, typically a few days, the air parcels lose 

their identity because of mixing. On the other 

Figure 7-6. om Tagish, 

Yukon, to Asia. 

Source: Bailey et al., 2000. 

Air movement back trajectories fr

7-8

Long-Range Environmental Transport of POPs 

hand, although the second, or dispersion modeling, 

approach includes these important processes, they 

are subject to considerable uncertainties. NOAA’s 

Air Resources Laboratory maintains a Web site 

(http://www.arl.noaa.gov/ready.html) for researchers on which it is possible to calculate trajectories 

extending either backward or forward for anywhere 

in either the Northern or Southern Hemispheres. 

Back trajectory models are particularly useful to 

ascertain the source of pollutants. For instance, 

high levels of a number of POPs, such as α-HCH, 

γ-HCH, DDT, and chlordane, were found in atmospheric samples at a monitoring site in Tagish, 

Yukon, Canada (Bailey et al., 2000). As shown by 

the trajectories in Figure 7-6, the pollutants were 

associated with long-range transport from Asia, 

occurring generally within the previous 5 days. 

Coupling emissions data with the trajectory methods can further inform inferences that POPs observed at monitoring sites came from particular 

source regions. 

The results of the calculation of a large number of 

backward trajectories can be assembled to trace 

“transport pathways” leading to a particular monitoring site. Several thousand trajectories from 

Alaska were calculated backward for 10 days during 

the entire year of 1999. Results for 4 months of 

the year (January, April, July, and October) are 

shown in Figure 7-7 to give an idea of the seasonal 

variation in the transport pathways through the 

atmosphere (Husar and Schichtel, 2001). The 

different-colored shading in Figure 7-7 reflects the 

probability that trajectories passed over a given 

area before arriving at the Alaska Peninsula National Wildlife Refuge in the Aleutian Islands. The 

boundaries of each shaded region represent lines of 

constant probability. The areas shaded in red have 

the highest probability of being traversed by trajectories, whereas those shaded in light blue have a 

lower probability. Similar calculations for a number 

of receptor sites throughout the United States are 

shown in Appendix A. By comparing the locations 

of the dust and smoke plumes shown in Figures 

7-1, 7-3, and 7-4 to the transport pathways shown 

in the figures in Appendix A, it can be seen that the 

plumes visible in the satellite images occur within 

defined transport pathways. Even though smoke or 

dust may not be visible in satellite images, the transport of other airborne compounds, including POPs, 

still occurs within these pathways. 

Figure 7-7. efers to the likelihood that 

trajectories passed over a given area before arriving at the receptor site. 

Source: Husar and Schichtel, 2001. 

Aleutian 10-day back trajectories for the year 1999. Color shading r

7-9

Long-Range Environmental Transport of POPs


During the springtime, after the winter snows have 

melted and before a vegetation cover has appeared, 

extensive clouds of yellow dust can be raised from 

the Gobi and Taklamakan Deserts (Duce, 1995). 

Strong cold fronts originating in Siberia are associated with strong upward air motions in front of 

them as they travel southward. The vertical motions carry whatever pollutants are found near the 

surface upward to the altitude of the jet stream, 

where they can be rapidly transported eastward to 

North America (Figure 7-3). Siberian cold fronts 

can travel all the way to southern China, so a broad 

range of pollutants from different regions can be 

transported to North America during a single frontal passage. Sinking air over northwestern North 

America allows suspended material in the air to be 

brought to the surface. It is only during the spring 

that the effects of these events are visible in satellite 

images. The frontal passages occur at other times, 

and may transport pollutants to North America 

without raising dust clouds. 

Figure 7-8 shows the results of a three-dimensional, chemistry-transport model simulation of the 

transport of dust from the Gobi Desert to North 

America during the dust storm of April 1998 

(Hanna et al., 2000). The “dust” plume shown in 

Figure 7-8 was produced by both horizontal and 

vertical motions. In general, long-range transport 

of pollutants involves movement vertically as well as 

horizontally. Events such as those shown in Figure 

7-8 result in rapid transport, on the order of a few 

days, over transcontinental distances. This simulation included emissions from different points within 

Asia and the effects of atmospheric mixing during 

the transport of the emissions. Emissions from 

different regions of Asia follow their own pathways 

to North America, where they affect different areas. Figure 7-8 also shows that transport does not 

terminate abruptly at the coast of North America; 

rather, there can be deposition on mountains near 

the coast and even further inland. The frequency 

of these events and their importance as a transport 

mechanism to North America remain to be determined. The next step will be to include in the 

model the chemical losses and multimedia transfers 

described above so that the transmission of POPs 

and other chemicals during intercontinental transport can be determined. 

The results of a three-dimensional, chemistrytransport model simulation of the global distribution of hexachlorobenzene (HCB), a long-lived 

POP, are shown in Figure 7-9 (Olaguer and Pinto, 

2001). The distribution of HCB was calculated 

using data for the emissions of HCB and loss by 

OH radicals calculated with the model. The areas 

of high concentration in Figure 7-9 basically result 

from a combination of high emissions and meteorological conditions that favor trapping emissions 

close to the surface. The model was able to simulate successfully a number of observed features of 

the global distribution of HCB, including its ratio 

between the Northern and Southern Hemispheres, 

lending credence to this approach. Simulations 

such as these will permit quantitative testing, by 

comparison with observations, of many of the 

concepts presented in this chapter. 

Figure 7-8. d trajectory simulation of dust from the Gobi Desert to North America, April 1998. 

Source: Hanna et al., 2000. 

Forwar

7-10

POPs Transport in Water

Long-Range Environmental Transport of POPs 

POPs Transport in Water 

Long-range transport can also occur through hydrologic pathways, with POPs entrained on sediment, in microscopic species, or in solution (for the 

more water-soluble compounds). POPs released or 

deposited onto terrestrial areas are transported 

down rivers to oceans, and then potentially to 

remote locations through oceanic currents. POPs 

deposited and accumulated on ice in the Arctic can 

also be transported into the North Atlantic by ice 

floes. The contribution of hydrologic transport to 

global POPs pollution has not been quantified, 

although it is generally considered to be substantially less than occurs through atmospheric transport of these semivolatile, hydrophobic substances. 

Oceanic currents can be wind generated at the 

ocean surface or result from water temperature and 

density (thermohaline) differences. Wind generated 

currents are generally limited to the first 1,000 

meters of depth, whereas thermohaline currents 

can extend down to the deep sea. Oceanic current 

speeds are highly dependent on location. Movement in the Gulf Stream or Kuroshio currents can 

be rapid (7–11 km/hr, 4–6 knots) over thousands 

of kilometers, whereas within localized gyres (circling currents) or deep oceanic regions little to no 

net water transport may be occurring. The major 

surface currents in the North Atlantic Ocean form a 

large gyre, or closed clockwise circulation, in which 

the Gulf Stream current flows northward along the 

east coast of North America to Cape Hatteras, NC, 

then travels to the northeast, then southward along 

the coast of Europe, and finally westward across 

the tropical Atlantic Ocean in the North Equatorial 

Current to close the circulation (Figure 7-10). 

A similar circulation pattern is found in the North 

Pacific Ocean, in which the Kuroshio current flows 

northward along the coast of Asia to the southeast 

coast of Japan through the East China Sea. Its 

width is about 100 km, its speed 6–7 km/hr (3–4 

knots), and it transports 30–60 million tons of 

water per second (Pickard, 1975). Pacific currents 

can transport POPs from Asia to continental Alaska 

and its island chains. The transit time around the 

Figure 7-9. face. 

Source: Olaguer and Pinto, 2001. 

Calculated global distribution of hexachlorobenzene at the earth’s sur

7-11

Long-Range Environmental Transport of POPs


Bering Sea was estimated in the order of 1 year, as 

measured by satellite tracking of drift markers 

(Royer and Emery, 1984). Measurements of the 

latitudinal distribution of POPs in seawater are 

sparse. Concentrations of at least one organochlorine, α-HCH, in seawater were found to increase 

with latitude by roughly a factor of 20 on a transect 

from the Java Sea to the Beaufort Sea (Wania and 

MacKay, 1996; and references therein). This 

increase is probably the result of atmospheric deposition. Although computer models of the ocean’s 

circulation exist and have been coupled with atmospheric models to study problems related to climate 

change, they have not yet been applied to problems of POPs transport. 

The ocean can also act as an ultimate sink for 

POPs, either through the deposition of dead biological organisms or via deep-current circulation. 

POPs can be concentrated up the marine food 

chain, starting with phytoplankton. Some POPs 

are transported to deeper layers of the ocean by 

settling phytoplankton, or “marine snow.” Evidence for this pathway is provided by elevated 

concentrations of POPs in marine fish, with higher 

concentrations found in deeper living varieties 

(Froescheis et al., 2000; Looser et al., 2000). 

Sinking water, such as part of the Gulf Stream near 

Iceland, also carries with it pollutants such as 

POPs. POPs transported to the deep sea by either 

of these pathways will probably remain there and 

be degraded, because it takes several hundred years 

for water in the deep sea to return to the surface 

again in a region of upwelling. 

POPs Transport by Migratory Animals 

POPs transport through migratory species is also 

considered a potential source of contaminant movement under the Stockholm Convention. Evaluation 

of this mechanism differs from the previous assessments of atmospheric and hydrologic transport, 

because POPs transported through migratory species are often focused on a localized region (lakes, 

nesting sites) or injected directly into the food supply. Through this means, the POPs concentration 

in lipid is maintained, dilution is prevented or minimized, and the POPs are potentially targeted at a 

Figure 7-10. Oceanic surface currents. 

Source: Adapted with permission from Apel, 1987. 

7-12

Long-Range Environmental Transport of POPs 

receptor animal species. This can be viewed as 

more of a stiletto approach, compared with the 

blunderbuss of atmospheric transport. 

The bulk amount of POPs transported long distances by migratory birds, fish, and/or marine 

mammals is highly uncertain, and estimates are not 

available (van de Meent et al., 2001). However, it 

has been calculated that the POPs loading from 

spawning and dying salmon swimming to localized 

lakes in Alaska is greater than air deposition levels 

(Ewald et al., 1998). POPs may also be transported by migratory birds to remote rookeries, and 

from there be transferred to resident species. Most 

importantly for high trophic predators and human 

risks, the oceanic movement of some fish and 

marine mammals can transfer the POPs loads 

obtained throughout this migratory journey directly 

to the end predator. 

Monitoring and Modeling POPs Trends 

Atmospheric monitoring and modeling provide reassurance that efforts on POPs can be, and are, 

effective in regions such as the Great Lakes. On 

the basis of data collected by the Integrated Atmospheric Deposition Network (IADN; www.epa.gov/ 

glnpo/iadn/), trends in concentrations of a number 

of key POPs can be calculated and extrapolated to 

give approximate dates when atmospheric concentrations will be beneath minimum detection limits of 

the measurement techniques used (i.e., “virtual 

elimination”; Cortes et al., 1998). Results of these 

extrapolations are shown in Figure 7-11. Atmospheric levels of DDT and DDD are predicted to be 

the first below detection limits, disappearing at all 

sites by about 2010. HCB will remain in the atmosphere the longest of all the compounds considered, mainly because of its continued production as 

a byproduct. Overall, though, these data suggest 

that most of the compounds will disappear from the 

atmosphere of the Great Lakes by the middle of 

this century. 

Acknowledgments 

The help of Dave Leonhard and Dianne Caudill in 

producing the figures is gratefully acknowledged. 

Dr. Rudolf Husar kindly supplied the calculations of 

Figure 7-11. 

atmospheric concentrations in the Great Lakes region. 

Virtual elimination date estimates assume no significant 

new sources. 

Source: Cortes et al., 1998. 

IADN virtual elimination dates for 

transport pathways used here. Helpful comments 

by colleagues including Drs. Eduardo Olaguer, 

Elliott Atlas, and Leonard Barrie are also gratefully 

acknowledged. 

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7-15

Contemplating POPs 

and the Future Chapter 8 

Treaties are guided by past experiences, negotiated in the present, and look to a better future. 

For the Stockholm Convention, a fundamental 

consideration is what the future might hold in 

decades to come in the absence of action. As with 

the accumulation of POPs in the environment, the 

passage of time necessitates thinking beyond the 

present day. What will be future sources and levels 

of POPs emissions, and could the Stockholm Convention affect these emissions? This chapter informs these considerations by summarizing the 

results of existing demographic and economic 

futures forecasts. The models demonstrate that 

future POPs source regions will likely be different 

from current ones, and that very large regional 

growth rates in human populations and economic 

and industrial activity could drive POPs emissions in 

the absence of controls. 

The futures modeling scenarios to be presented 

were developed and reviewed as part of the Intergovernmental Panel on Climate Change (IPCC) 

research program. Rather than estimate specific 

POPs emissions, the models focus on the growth in 

current economic activities in which POPs are used 

or emitted under current production and use patterns. The intent is to indicate the general pattern 

of economic growth and important sectoral components of these activities. Results are presented 

for the Special Report on Emission Scenarios 

(SRES) B2 scenario, one of the four basic classes 

of scenarios developed for the recent IPCC report 

(IPCC, 2000). The SRES B2 scenario was selected 

because it falls roughly in the center of future projections of population and economic activity, yet is 

relatively optimistic about the future of presently 

developing countries and does not contain major 

new policy initiatives. Most of the data presented 

come from the MiniCAM (Edmonds, 1985, 1996) 

version of the B2 scenario developed and submitted to the Special Report by the Global Change 

Group (GCG) at Battelle Pacific Northwestern 

National Laboratories (PNNL) (IPCC, 2000; pp. 

566-570), or, in some noted instances, from recent 

revisions based on model improvements. Results 

from the Second Generation Model (SGM), the 

GCG’s larger and more detailed emissions model 

(Edmonds et al., 1995), were used for some of the 

detailed sectoral results. The SGM model run used 

for these results largely reproduces the aggregate 

population and economic activity patterns of the 

PNNL MiniCAM B2 model, acting as an internal 

validity check of the results expected in a “B2 

future world.” 

The SRES B2 projection is commonly considered 

the “business as usual” scenario. Such a scenario 

assumes a continuation of past trends in population, technologies, and industrial output, with no 

major shifts in government policy. This forecast is 

the basis for all U.S. Administration energy and 

climate change analyses. For the forecasts included in this chapter, U.S. population and gross 

domestic product (GDP) trajectories have been 

modified from the SRES (IPCC, 2000) report to 

track the most recent Annual Energy Outlook 

forecast (U.S. DOE, 2000). Results are modeled 

to the year 2050. It is important to recognize 

that population, GDP, and the nature and structure of economic activity can be quite different 

from the values given here. Using B2 as a representative case should not be interpreted to 

mean that this is the most likely situation. It is 

used because it provides a good qualitative sense 

of how activities leading to POPs emissions 

might grow in the absence of additional control 

strategies. 

The results of the B2 model runs are presented 

under two basic categories: general growth and 

sector-specific results. The general growth categories are factors such as population, economic, 

8-1

Contemplating POPs and the Future


and industrial growth that act as potential pollution drivers. These general growth drivers are 

not necessarily linearly associated with environmental pollution, as economic growth and prosperity have also led to enhanced pollution awareness and the means to combat it. The 

sector-specific forecasts have been selected for 

their potential relevance to one or more of the 

listed POPs in developing countries. For instance, if the use of chlordane and other POPs 

termiticides is continued, the emission levels 

would likely relate to such factors as housing 

starts. Byproduct POPs emissions have come 

from municipal and hospital waste incineration, 

open burning of wastes, chlorine bleaching of 

pulp and paper, and iron and steel sintering, 

among others. In the absence of control technologies as economies develop, future byproduct 

emissions from these sources could reasonably be 

expected to increase, with the sectoral projections acting as a proxy for these emission increases. 

General Worldwide Growth Projections 

Population Growth 

Human population growth is central to all pollution scenarios. All of the POPs were either developed and produced to satisfy contemporary 

human needs, or are the byproducts of human 

activities. Figures 8-1 and 8-2 provide forecasts 

of human population growth rates and projected 

levels by region. The population forecast used 

here closely mirrors the most recent United NaFigure 8-1. Projected declining annual rates of world 

population growth. 

World Population Growth Rate 

Figure 8-2. Projected world population levels, by region. 

ROW, rest of world; EEFSU, Eastern Europe Former 

Soviet Union; OECD, Organization for Economic 

Cooperation and Development. 

tions median forecast (Population Division; 

United Nations, 2000) that the total world population will reach 9.3 billion by 2050. As evident 

in Figure 8-1, the projected global population 

growth rate is decelerating, although it remains 

uncertain how long this trend will continue. The 

global average rate conceals large variations 

across regions, with the Rest of the World (ROW) 

region continuing to grow rapidly, whereas the 

population is declining in all Organization for 

Economic Cooperation and Development 

(OECD) countries, except the United States. 

The projection of total world population (Figure 

8-2) demonstrates that population increases will 

likely be concentrated in three areas, the largest 

being the rest of the world category, comprised 

principally of Latin America and Africa in this 

graph. China and India are the other two large 

contributors, with the Chinese population estimated to have peaked by 2030 and in a slow 

decline by 2050. The Indian population, in 

contrast, continues to grow, although not as 

rapidly as Africa and Latin America. The current group of developed countries will constitute 

only about 10% of the world population by 2050. 

The global population will be much older on 

average than it is today, with the average age 

increasing from 26 to 36 years (United Nations, 

2000). 

8-2

Contemplating POPs and the Future 

Economic Activity 

In contrast to the ~50% growth in population, 

global economic activity is projected to increase 

fourfold, from US$22 trillion in 1990 to $88 

trillion in 2050 (in 1990 U.S. dollar equivalents). 

Average per capita income will more than 

double. The overall pattern of economic activity 

shows a large shift from its current focus in North 

America and Europe to Asia, Africa, and Latin 

America (Figure 8-3). Half the growth in economic output will occur in these areas, with their 

share of economic activity projected to rise from 

16% to 41% over the half-century. The growth 

in ROW GDP is especially large, reflecting a 

combination of rapid population growth and 

increase in per capita income from just over 

$1,000 per capita to about $4,500 per capita. 

Because these areas currently have quite low per 

capita income levels, it is anticipated that much 

of this growth will go to the provision of essential 

physical commodities, such as infrastructure and 

appliances. In contrast, the economic growth in 

the currently developed economies will likely be 

focused in areas such as services, which are less 

intensive users of such inputs as energy and 

chemicals. The likelihood exists, therefore, that 

much of the growth in potential POPs-producing 

activities could occur in developing countries. 

Figure 8-3. Projected growth in worldwide gross domestic 

product (GDP). , rest of world; EEFSU, Eastern 

Europe Former Soviet Union; OECD, Organization for 

Economic Cooperation and Development. 

ROW 

ASIA 

EEFSU 

OECD90 

ROW

Figure 8-4. Projected increases in worldwide agricultural 

output. , rest of world; EEFSU, Eastern Europe 

Former Soviet Union; OECD, Organization for Economic 

Cooperation and Development. 

ROW 

ASIA 

EEFSU 

OECD90 

ROW

Agricultural Output 

The pattern of agricultural production shows a 

similar, although less pronounced, shift from 

developed to developing countries (Figure 8-4). 

The models predict a nearly 21⁄2-fold increase in 

agricultural output worldwide, with the OECD 

share falling from about two-thirds to just over 

one-half. Data from similar scenarios in the 

SRES database (CIESIN, 2001) suggest that this 

growth in output will occur with only minimal 

growth in land area allocated to agricultural production, implying a significant increase in intensity of production and a corresponding increase 

in agricultural chemical use. 

Figure 8-5. Projected growth in worldwide electricity 

consumption. , rest of world; EEFSU, Eastern 

Europe Former Soviet Union; OECD, Organization for 

Economic Cooperation and Development. 

ROW

8-3

Contemplating POPs and the Future


Energy Consumption 

Total energy consumption and associated gaseous and particulate emissions serve as an additional proxy for economic development. Total 

electricity consumption is predicted to grow by 

more than a factor of six, rising from 35 Ej 

(exa-, 1018 joules) in 1990 to 233 Ej in 2050 

(Figure 8-5). The proportion of electricity consumed outside OECD countries also rises rapidly, 

from 38% in 1990 to 79% in 2050. Although 

the fraction of electricity generated by fossil fuel 

inputs declines slightly during the 1990-2050 

period (60% to 52%), the strong growth in elecFigure 8-6. Projected worldwide emissions of carbon 

dioxide from the energy sector. , rest of world; 

EEFSU, Eastern Europe Former Soviet Union; OECD, 

Organization for Economic Cooperation and 

Development. 

Figure 8-7. Projected worldwide declines in sulfur 

emissions as a result of improved technologies. , 

rest of world; EEFSU, Eastern Europe Former Soviet 

Union; OECD, Organization for Economic Cooperation 

and Development. 

ROW

ROW

tricity demand is predicted to increase global 

CO2 emissions from 5.6 billion tonnes to 12.1 

billion tonnes (Figure 8-6), with the developingcountry proportion rising from 59% to 77%. 

Sulfur emissions provide an important 

counterexample to the general upward trend in 

emissions and economic activity. Despite the 

rapid growth in electricity use and coal-fired 

plants, sulfur emissions are expected to decline 

sharply over the next half-century (Figure 8-7). 

This decline results from the development and 

application of control technologies, a situation 

somewhat analogous to the potential for POPs 

byproduct controls under the Stockholm 

Convention. 

Sector-Specific Growth Projections 

The preceding demographic and economic factors 

act as general—but nonspecific—drivers of pollution and POPs levels. In some instances, specific 

sector models are available that more closely link 

economic activity with one or more POPs. Two 

such examples are summarized below: housing 

starts and termiticide use; and municipal waste 

generation and selected industrial production categories and potential byproduct emissions. Although the links between these sectoral projections 

and potential POPs releases are indicated, no 

attempt is made to perform further modeling beyond the existing projections. 

Housing Starts and Termite Control 

Of the POPs pesticides, chlordane (along with 

heptachlor and mirex) continues to be used for 

household termite control in both wood and brick 

construction in a number of developing countries. 

Chlordane is relatively cheap and provides longlasting termite control in the soil beneath and 

around houses, but ultimately may be released 

into the environment and transported far from its 

site of application. Alternative non-POPs pesticides, physical barriers, and construction techniques are available for termite control, but the 

sheer persistence and toxicity of chlordane is still 

considered by some to be a substantial asset in 

the struggle against termites, especially in the 

8-4

Contemplating POPs and the Future 

tropics. With cessation of production in the 

United States, China commenced chlordane 

manufacture and has requested an exemption for 

production and use as a termiticide in buildings 

and dams. Several other countries have requested use exemptions for chlordane as a 

termiticide (UNEP, 2001). 

Sector-specific projections indicate that growth in 

households worldwide will be substantial, because 

of the overall growth in population and as that 

population ages and becomes more urban. The 

estimates provided here reflect only the aging and 

population growth components, but not the impacts of urbanization. They are based on agespecific head of household rates from MacKellar 

et al. (1995) (Figure 8-8). Total annual new 

household formation is projected to reach nearly 

35 million by 2015 and then slowly decline to 

below 25 million annually by 2050. Almost all of 

this new household formation and related construction will occur in the developing world. 

Municipal Waste Generation 

and POPs Byproducts 

Polychlorinated dioxins and furans are principally 

formed and released from the poor or uncontrolled combustion of municipal and hospital 

wastes, particularly open burning, resulting from 

a combination of poor burn parameters, organic 

matter, chlorine, and metal catalysts. Although 

data quality issues exist for projections of solid 

waste generation, enough is known to indicate 

that the solid waste stream will grow rapidly over 

the next half-century. A recent World Bank 

report suggests two drivers for this growth: an 

increase in urban populations and an increase in 

Figure 8-8. Projected worldwide new household 

formation. , rest of world; EEFSU, Eastern Europe 

Former Soviet Union; OECD, Organization for Economic 

Cooperation and Development. 

ROW

the income of urban dwellers. Urban dwellers 

generate several times more waste than do 

rural dwellers (World Bank, 1999) (Table 8-1). 

Wealthy urban dwellers generate about 2.5 times 

more waste per capita than do poor urban dwellers. Over just 25 years, Asia is predicted to 

move from about 30% to more than 50% urban 

dwellers. Forecasts suggest that the rest of the 

developing world will follow a similar pattern. 

The World Bank study estimates an overall 

growth in municipal solid waste of 2.4-fold by 

2025, to a total of two-thirds of a billion tons 

annually in Asia alone. The waste stream is 

forecast to become more combustible and organic in composition, making incineration an 

increasingly attractive option, while landfills become more scarce. 

Table 8-1. 

1990 2025 

GNP/ MSW/ GNP/ MSW/ 

Region Capita % Urban Capita Capita % Urban Capita 

Low-income Asia 490 27.8 0.64 kg 1,050 48.8 0.77 kg 

Middle-income Asia 1,410 37.6 0.73 kg 3,390 61.1 1.17 kg 

High-income Asia 30,990 79.5 1.64 kg 41,140 88.2 2.17 kg 

Recent and projected municipal solid waste (MSW) generation per capita in Asia 

8-5

Contemplating POPs and the Future


Industrial Processes and POPs Byproducts 

Other sources of polychlorinated dioxin and furan 

byproducts listed in the Stockholm Convention 

include elemental chlorine bleaching of pulp and 

paper, iron ore sintering, and secondary metals 

production, such as poorly performed recycling 

through incineration of copper and other metalcontaining items. Projected production increases 

under these sectors are shown for a subsection of 

regions where data are available. The extent to 

which production increases translate to POPs 

emission increases is highly dependent on the 

development and use of pollution prevention and 

control practices. 

The model results for wood production, relevant 

to the extent they can be considered a proxy for 

pulp and paper manufacture, demonstrate an 

approximate fourfold increase over 50 years, 

reasonably uniform across all regions (Figure 8-9). 

Total steel production, a proxy for iron ore sintering, is projected to increase threefold by 2050 in 

the same five regions (Figure 8-10). China is 

projected to be the largest steel producer by the 

end of this period, with Japan and the United 

States remaining significant producers. Nonferrous metals are a much smaller part of production, and model results are available for only four 

regions. Absent data for China, the production 

picture for the four other regions remains dominated by the United States and Japan, with 

somewhat slower growth than for steel (graph not 

shown). 

Figure 8-9. Projected wood products production from 

selected countries. 

Figure 8-10. Projected iron and steel production from 

selected countries. 

It bears noting that other POPs also have continuing connections to demographic and economic drivers in the absence of additional controls. DDT use continues for malaria vector 

control in the tropics, where projected increases 

in human populations are accompanied by a 

possible expansion of the range of the vector. 

Country-specific exemptions exist under the 

Stockholm Convention for limited continued use 

of the pesticides mirex, heptachlor, aldrin, and 

dieldrin, principally for termite, ant, and locust 

control. Hexachlorobenzene production continues as an industrial intermediate and byproduct 

of chemical manufacture and incineration, and 

PCBs remain worldwide awaiting equipment 

retirement and destruction or environmentally 

sound disposal. Agricultural use of a number of 

POPs also continues in some countries contrary 

to national laws, and the potential exists for 

future POPs development for agricultural or industrial purposes in the absence of an implemented Stockholm Convention. 

Summary 

There will be large increases in the scale of worldwide economic activity over the next half-century, 

with overall economic activity predicted to increase 

about fourfold. Individual economic and end-use 

activities that either use or emit POPs can increase 

by more or less than this overall growth rate, depending on the specifics of the activity and its 

8-6

Contemplating POPs and the Future 

growth. Except for activities directly linked to 

population increases, such as new households or 

populations in mosquito-prone areas, none of the 

sectors is expected to grow by less than a factor 

of two, some growing by as much as sixfold. 

The Special Report on Emission Scenarios 

(IPCC, 2000) considers many scenarios other 

than those presented here, some with much 

higher levels of per capita incomes and lower 

populations, others with lower levels of economic 

well-being and higher populations. Yet all of 

these projections share a future of much higher 

total economic activity, and hence of potential 

uses and emissions of POPs in the absence of 

active control policies. 

References 

Center for International Earth Science Information Network (CIESIN). 2001. http://sres.ciesin.org/. 

Edmonds J, Pitcher HM, Barns D, Baron R, Wise MA. 

1995. Modeling future greenhouse gas emissions: the 

second generation model description. In: Modelling 

Global Change. Tokyo: United Nations University Press, 

October 1995. 

Edmonds J, Reilly J. 1985. Global Energy: Assessing 

the Future. New York: Oxford University Press, p. 317. 

Edmonds J, Wise M. 1996. Stabilizing atmospheric 

CO2

: rethinking the emissions problem. In: An Economic Perspective on Global Climate Change. Washington, DC: American Council for Capital Formation. 

Intergovernmental Panel on Climate Change. 2000. 

Special Report on Emissions Scenarios. Cambridge 

University Press. 

MacKellar FL, Lutz W, Prinz C, Goujon A. 1995. Popu21(4):849-865. 

lation, households, and CO2 emissions. Pop Dev Rev 

U.S. Department of Energy (U.S. DOE). 2000. Annual 

Energy Outlook 2001. DOE/EIA-0383(2001), December 2000. http://www.eia.doe.gov/oiaf/aeo/index.html. 

United Nations. 2000. Population Division, Department 

of Economic and Social Affairs. World Population Prospects, The 2000 Revision, Highlights. February 2000. 

http://www.un.org/esa/population/wpp2000h.pdf. 

United Nations Environment Programme. 2001. Revised list of requests for specific exemptions in Annex A 

and Annex B and acceptable purposes in Annex B 

received by the secretariat prior to commencement of 

the Conference of Plenipotentiaries on 22 May 2001. 

UNEP/POPs/CONF/INF/1/Rev 3. 14 June 2001. 

World Bank. 1999. What A Waste: Solid Waste Management in Asia. http://www.worldbank.org/html/fpd/ 

urban/publicat/waste.pdf. 

8-7


Reflecting the dynamic societal, scientific, and 

industrial time in which we live, the Stockholm 

Convention anticipates change through the ability 

to list additional persistent organic pollutants 

(POPs) as new science becomes available. The 

United Nations Environment Programme (UNEP) 

mandate for the POPs negotiation had limited 

initial consideration to the twelve substances or 

substance groups. By doing so, negotiators were 

able to focus on developing generic procedures for 

addressing POPs, based on the “dirty dozen,” 

rather than digressing into potentially controversial 

discussions over additional chemicals that might be 

added. The mandate emphasized, however, “the 

need to develop science-based criteria and a procedure for identifying additional persistent organic 

pollutants as candidates for future international 

action.” This task was undertaken by technical 

experts at criteria expert group (CEG) meetings in 

Bangkok (1998) and Vienna (1999), and during 

subsequent negotiations. The resulting process and 

criteria for the addition of chemicals are codified in 

Article 8 and Annexes D, E, and F of the 

Stockholm Convention, respectively 

(www.unep.ch). This chapter summarizes the 

technical foundation and science-policy basis considered in developing these criteria and procedures, 

accompanied by contemporary advances in science 

from the published literature. 

Noteworthy in technical discussions on the addition 

of chemicals was the speed with which consensus 

was reached among scientists at the CEG meetings. Numerous factors contributed to this consensus, among them: criteria precedents, e.g., 

UNECE-LRTAP; the “scientific method” based on 

the provision of data to support opinions; and 

external academic, industry, and nongovernmental 

organization (NGO) involvement. Of paramount 

importance, though, was the inexorable weight of 

evidence gathered and widespread action already 

The Addition of Chemicals— 

A Living Agreement Chapter 9 

taken against POPs. 

industry and pesticide manufacturers seek to 

commercialize a substance with POPs characteristics, particularly if there is the possibility of a 

dispersive use. 

PBT (persistent, bioaccumulative, toxic) chemicals predates the domestic PBT guidelines and 

actions, and can be seen as responsive to technical, economic, and environmental concerns about 

the impacts of POPs. 

Over the decades, the academic community has 

also provided scientific input from research on 

the ecological and human health problems stemming from POPs. 

to deliberations in the United States and Canada 

on the UNEP POPs negotiation was consolidated 

through the 1998 SETAC Pellston Workshop on 

the “Evaluation of Persistence and Long-Range 

Transport of Organic Chemicals in the Environment.” 

al., 2000) provides an excellent technical summary on persistence and long-range transport. 

The weight of evidence against POPs is also supported by the number of previous domestic, bilateral, and international technical reviews and policy 

interventions to identify and address this group of 

chemicals. 

the domestic actions and international POPs/ 

PBT agreements are listed in Table 9-1. The 

differences in screening criteria values should be 

interpreted in light of the geopolitical scope of 

each initiative. 

range, the higher the screening criteria values 

because the more problematic a substance must 

be to cause transboundary effects at this distance. 

POPs screening values is the recognition that 

they complement domestic initiatives. 

POPs contamination occurs close to the site of 

Only rarely now do U.S. 

This reticence to develop POP/ 

Input from research scientists 

The report of this workshop (Klecka et 

The screening criteria used in many of 

The broader the geographic 

Integral to interpreting the international 

Most 

9-1

Addition of Chemicals


Table 9-1. National and international screening criteria for POPs 

a The “&” terminology should be applied before the “or” term, such that a chemical must have an air half-life greater than 2 days plus the vapor pressure requirement, or this combination could be 

substituted by remote measurements. 

b The Stockholm Convention and UNECE-LRTAP POPs Protocol state that alternative criteria may be considered if there is evidence that the substance is otherwise sufficiently persistent or 

bioaccumulative to make it of concern within the scope of the Convention. 

c The air half-life is sufficient for meeting the persistence requirement. Vapor pressure maxima were incorporated to exclude highly volatile substances. 

release. But because of the propensity of these 

chemicals to persist, bioaccumulate, and be 

transported long distances, POPs contamination 

is dispersed widely and cannot be mitigated 

solely through domestic activity. Exacerbating 

the transboundary nature of POPs contamination 

are ecosystem peculiarities, particularly in the 

polar regions where cold temperatures and the 

high lipid content of animals make these areas 

especially vulnerable to adverse effects. 

The Addition Process 

All the POPs agreements in Table 9-1 anticipate 

the addition of substances through a process of 

screening followed by a more detailed technical 

assessment. Under the Stockholm Convention, 

the scientific and technical work necessitated by 

these activities will be performed by a Persistent 

Organic Pollutants Review Committee (POPRC). 

The following general procedures will be 

followed: 

1.	 Screening (process Articles 8-1 to 8-5; 

criteria Annex D): Screening acts as a 

mechanism to exclude chemical proposals 

that have insufficient data or do not fulfill the 

screening criteria, thereby facilitating 

efficient use of technical experts. 

2.	 Risk profile (process Article 8-6; Annex E): A 

detailed technical report is prepared expanding on the screening criteria data and additional information requirements and assessing 

if: “the chemical is likely as a result of its 

long-range environmental transport to lead to 

significant adverse human health or ecological 

effects such that global action is warranted.” 

9-2

Addition of Chemicals 

3.	 Risk management/socioeconomic 

considerations (process Article 8-7; Annex 

F): Subsequent to an affirmative finding from 

the risk profile, management options are 

evaluated for the proposed substance, taking 

into consideration technical and socioeconomic considerations. 

4.	 Recommendation to, and decision by, the 

Conference of the Parties (COP; process 

Article 8-9): Based on the risk profile and 

management options, a technical 

recommendation is made to the COP whether 

a chemical should be considered for listing in 

Annexes A, B, and/or C and what control 

measures should be invoked. Ultimate 

decisionmaking rests with the COP. Set-aside 

and review procedures are detailed in Articles 

8-5 and 8-8. 

5.	 Ratification of amendments (Article 22-4): 

Each Party to the Stockholm Convention may 

opt to review its concurrence with the 

addition of each new chemical to the 

Annexes. For the United States, entry into 

force for additional chemicals is likely to 

require an affirmative statement agreeing to 

be bound by this addition, although domestic 

implementation details have not been 

finalized. 

Scientific Foundation for 

Adding Chemicals 

The basic process for adding POPs chemicals is 

consistent across a range of international agreements (UNECE-LRTAP, 1998; NAAEC, 1998) and 

with the conclusions of scientific bodies charged 

with developing such procedures (CEG, 1998; 

Klecka et al., 2000). The process and criteria 

recognize the complexity of real world environments, and the necessary balance between codifying indicative guidance criteria versus flexibility 

and the need for expert judgment. Earth’s environments vary from steamy, microbe-rich jungles 

to frozen waters and anerobic sediments, all of 

which may play a part in the environmental fate 

of a POP. Reversing this scenario, the many and 

varied physico-chemical properties of the individual POPs influence how they pass through, 

accumulate, and sequester in and over the Earth. 

This section summarizes the technical considerations in evaluating a substance for inclusion as a 

POP. Additional details on screening criteria 

development can be obtained from Rodan et al. 

(1999); on persistence, transport, and modeling 

from Klecka et al. (2000); and on bioaccumulation from the Great Lakes Water Quality 

Criteria support documents (U.S. EPA, 1995). 

Screening Criteria 

Annex D of the Stockholm Convention provides 

a hierarchical structure for the initial screening of 

POPs candidates. This screening requires satisfying 

all four criteria categories of (1) persistence, (2) 

bioaccumulation, (3) long-range environmental 

transport, and (4) adverse effects (toxicity). Flexibility and expert judgment are stipulated, however, 

wherein a low value for one criterion should be 

weighed against values for other criteria and environmental fate and monitoring considerations. 

Persistence 

Persistence is the ability of a substance to remain 

in the environment. It is measured as either a 

half-life (time for half the amount of substance to 

degrade) or a residence time (average time for a 

molecule to remain in that environment = halflife  0.693). These measurement units assume first-order decay kinetics, which is considered a reasonable assumption at the 

screening stage (Klecka et al., 2000). As detailed in Table 9-1, persistence screening values for the Stockholm Convention and UNECE-LRTAP POPs Protocol are set at a 

half-life of 2 months in water or 6 months in 

soil or sediment, or evidence that the chemical 

is otherwise sufficiently persistent to justify its 

consideration. The numerical values are tacitly 

based on temperate climates, where much of 

the research has taken place. Persistence 

times can increase dramatically in dark (buried), cold (polar), sterile, or dry (desert) environments. It is recognized that such data 

should not be misused to inappropriately 

torque a chemical into meeting the screening 

guidance values. Application of the screening 

9-3

Addition of Chemicals


criteria also anticipates consideration of the 

environmental medium into which the POP is 

released, preferentially distributed (air, water, 

soil, and/or sediment), and passes through in 

its transboundary movement (i.e., before it can 

reach cold environments such as the Arctic; 

Klecka et al., 2000). 

Persistence in water, soil, or sediment is necessary for the chemical to be available for uptake 

by organisms, as a means of physical accumulation, and as a reservoir for, or receptor of, longrange environmental transport. The mechanism 

by which persistence leads to the buildup of 

chemicals in the environment is demonstrated in 

Figure 9-1. For this theoretical scenario, Figure 

9-1a plots the accumulation over time of two 

hypothetical chemicals with half-lives of 1 and 12 

months, in either soil, water or sediment. Two 

modes of release to the environment are shown 

for each chemical. The first models a single 

release of one hypothetical unit of chemical at 

the start of each year, and the second assumes a 

continuous release totaling one unit per year. 

The release of chemicals at the start of each 

year, such as would occur with once-annual pesticide application, leads to an immediate increase 

of 1 unit, followed by decline over the remainder 

of the year. Annual repetition leads to the sawtooth appearance. Continuous release over the 

entire year, such as from an ongoing byproduct 

emission, results in a roughly linear increase in 

the environmental concentration until steady 

state is reached. At steady state for both release 

scenarios (after ~5+ half-lives), the amount emitted to the environment equals the amount degraded, the latter being a function of the total 

accumulation in the environment. 

Taken a step further, Figure 9-1b graphs the relationship between chemical half-life and the concentration at steady state. In other words, based on 

steady state having been reached for all chemicals, the graph displays the resulting steady-state 

level for each and every chemical half-life. This 

figure demonstrates that there is no theoretical 

cut-off value for persistence that separates a 

problematic chemical from a nonproblematic 

one. Indeed, the accumulated concentration (C) 

in the environment at steady state is linearly 

proportional to the half-life (T1/2), following the 

equation C = RT1/2 / ln 2, where R is the application rate (Rodan et al., 1999). The 

longer the half-life, the greater the amount of 

physical accumulation that occurs. As can be 

demonstrated by extending Figure 9-1b, a 

chemical with a half-life of 10 years will build up 

Figure 9-1a. Accumulation curves. Upper graph half-life 

12 months, lower graph half-life 1 month. 

annual application of one unit leads to the saw-tooth 

appearance. 

year leads to the smooth curve. 

Source: Rodan et al., 1999. 

Figure 9-1b. Accumulation curves. Central line represents 

continuous release totaling one unit per year. Upper and 

lower lines bound the oscillation from a single release of 

one unit repeated annually. 

Source: Rodan et al., 1999. 

Repeated 

Continuous application of one unit over the 

9-4

Addition of Chemicals 

in the environment over a half century of use to 

a concentration 14 times the concentration that 

would have resulted from a single, annual application. This represents physical accumulation in 

the environment and is distinct from bioaccumulation (to be discussed shortly). Any physical 

accumulation in the environment increases the 

potential for exposure to, and bioaccumulation 

in, living creatures. 

Another approach to setting screening criteria for 

POPs is to examine measured laboratory and 

field data for substances already widely acknowledged to be of concern, e.g., the “dirty dozen,” 

compared with data on other substances that are 

not considered POPs (Figure 9-2). These data 

can then be compared with proposed criteria 

guidance values, marked here in gray at a persistence of 6 months and a bioaccumulation factor 

of 5,000. All 12 priority POPs (marked in red) 

or their POPs transformation products (aldrin 

converts to dieldrin, heptachlor to heptachlor 

epoxide) exceed degradation and 

bioaccumulation screening criteria adopted under 

the Stockholm Convention, usually by large margins. The extent to which these POPs exceed 

the screening criteria is obscured by the truncation of soil half-lives (necessary for ease of presentation) and the logarithmic scaling of the 

bioaccumulation axis. Similar findings are evident from graphs of overall environmental persistence generated by multimedia fate models 

(Rodan et al., 1999). 

Bioaccumulation 

Bioaccumulation is the buildup of a chemical in 

organisms compared with their surrounding 

physical environment. For POPs, bioaccumuFigure 9-2. Bioaccumulation v. half-life in soil. Gray shaded bars represent POPs screening criteria. The 

bioaccumulation factor is normalized to 5% lipid; the persistence times are truncated at three years. 

UNEP POPs are listed in red; additional LRTAP POPs in blue. 

Source: Rodan et al., 1999. 

9-5

Addition of Chemicals


lation generally relates to water insolubility and 

the propensity of these substances to accumulate 

in lipid media—animal fat. An indirect measure 

of this propensity to accumulate is the octanolwater partition coefficient (Kow), which measures the ratio of the equilibrium concentration in 

an organic medium (n-octanol) compared with an 

adjoining water medium. The Stockholm Convention screening criterion for bioaccumulation is 

centered on a bioaccumulation/bioconcentration 

value of greater than 5,000 in fish (Table 9-1), 

supplemented by additional evidence of 

bioaccumulation potential sufficient to justify its 

consideration. 

Figure 9-3 graphs the logarithm (base 10) of the 

bioaccumulation values in fish for a number of 

organic chemicals (the 12 POPs in red) compared with their corresponding log10 

octanol-water partition coefficients (log Kow; 

data reported in Rodan et al., 1999). A log 

scale is necessary for this graph because of the 

extreme Kow and bioaccumulation values for the 

POPs. A base 10 logarithm value of 5 equals 

105, or 100,000; 106 = 1,000,000; and 103.7 = 

5,000 (which is the BAF/BCF screening value in 

the Stockholm Convention). If Figure 9-3 had 

been graphed on a linear scale with the BCF value of 1 set at 1 millimeter height, then the page 

Figure 9-3. 10 octanol-water partition coefficient (Kow). Bioaccumulation 

factor is normalized to 5% lipid. ed (square marker), additional LRTAP 

POPs in blue (circle marker). 

Source: Rodan et al., 1999. 

Bioaccumulation in fish v. log

UNEP POPs are graphed in r

9-6

Addition of Chemicals 

would need to be more than 3 kilometers (2 

miles) long to fit the PCB bioaccumulation value 

of >3,000,000. 

In addition to confirming the extreme BAF/BCF 

values for the POPs, Figure 9-3 also demonstrates a number of technical issues pertinent to 

bioaccumulation and which factor into the appraisal of screening values: 

❊ There is an approximately linear relationship between the octanol-water partition 

coefficient and bioaccumulation for the 

majority of the organic chemicals (see Isnard 

and Lambert, 1988), albeit not for the 

organometals. This relationship provides a 

mathematical link between the screening 

values of logKow >5 and BCF/BAF >5,000. 

❊ The slope of this graph increases after 

logKow values of ~5, demonstrating 

biomagnification in the food chain. 

❊ The metabolism of some organic chemicals 

in more phylogenetically developed species 

can limit bioaccumulation, in this case demonstrated by differences in benzo[a]pyrene 

bioaccumulation between snails and fish. 

❊ The majority of organic chemicals (bottom left 

of graph) do not possess the extremes of 

bioaccumulation exhibited by POPs. 

Recall that the combination of data on two of the 

four POPs screening values in Figure 9-2 

(bioaccumulation and soil persistence) commences 

a process of separating chemicals that may pose 

transboundary or global problems from the majority of organic chemicals. The inclusion of data on 

the remaining two screening factors of toxicity and 

long-range environmental transport further informs 

this separation. 

Long-Range Environmental Transport 

Fundamental to the need for a global POPs convention is the transboundary nature of the problem, on a scale greater than can be resolved 

through bilateral or even regional agreements. 

With this understanding, the long-range environmental transport criterion can be informed by 

either (1) measured or monitored levels distant 

from sources of release to the environment or (2) 

modeling of a substance’s environmental fate 

properties, compared with known POPs substances. 

Measured levels of potential concern in remote 

locations distant from sources of release can 

unambiguously satisfy the long-range transport 

criterion. Indeed, the long-range transport properties of many of the “dirty dozen” were originally highlighted by their being found at significant levels in remote locations, such as the Arctic 

and mid-Pacific. It would be inappropriate, 

however, to await elevated levels in remote locations before anticipatory action is taken: thus, 

the additional criterion options of monitoring 

levels in transport media and modeling based on 

chemical properties. 

For transport monitoring and modeling, it has 

been demonstrated that the substance’s persistence in the transport medium (air or water) 

strongly governs the distance traveled (Rodan et 

al., 1999; Klecka et al., 2000). This analysis of 

persistence in a transport medium differs from 

the theoretical soil persistence analysis presented 

above, because it incorporates a finite time 

limitation, namely the time necessary for a substance to move from source to site of deposition. 

The key question is how long a substance needs 

to remain airborne or waterborne to constitute a 

problem warranting international action. This 

time period is directly related to the geographic 

scale of interest. For a global negotiation, that 

scale can be considered the transoceanic or 

transcontinental distance. Assuming a scale of 

ca. 4,000 kilometers (2,500 miles), it can be 

shown that approximately 7 to 10 days would be 

required for atmospheric transport from source 

to site of deposition. This assumption is based 

on average air movement rates across the 

United States of 7 m/sec (Draxler et al., 1991) 

and computer modeling of air movement on a 

global scale (Mason and Bohlin, 1995). As demonstrated in Figure 9-4, for a chemical with a 2-

day degradation half-life in air, the amount remaining after this approximate 8-day period is 

9-7

9-8

Addition of Chemicals

1/16 (2-4) of the original release. 

spheric half-lives lead to considerably smaller

residual amounts after 8 days, due to the shape

of the mathematical relationship between the

proportion of chemical remaining at time t

(mt

/m0) and the half-life (τ1/2) [mt/m0 =

exp(–ln(2)t/τ1/2)]. 

of a 2-day half-life screening guidance for degradation in air.

A similar analysis can be performed for water

transport, although it will be more complex because water movement rates are considerably

slower and much more variable. 

vides oceanic surface current estimates in the Pacific and Atlantic Oceans based on drifter analysis

(www.aoml.noaa.gov/phod/dac/dacdata.html).

The scale for the arrows of 25 cm/sec is equivalent

to 0.9 km/hr or 0.56 mph. 

ter 7, rapid oceanic currents are evident for the

Gulf Stream (U.S. East Coast) and Kuroshio current

(east Asia). 

are estimated at around 10 cm/sec (0.36 km/hr)

(Klecka et al., 2000). 

rapidly move large masses of water long distances.

For instance, the Gulf Stream off the U.S. East

Coast has a speed of around 1 knot (1.7 km/hr)

off Cape Hatteras, up to 6 knots (10 km/hr) maximum, and transports as much as 100 million cubic

meters of water. 

1–3 km/hr in nonflood situations.

To account for this variability in oceanic current

speeds, Figure 9-6 presents a modified version

of the theoretical analysis presented for air in

Figure 9-4. 

transport distance at 4,000 kilometers (2,500

miles), but this time plots oceanic current speed

on the x-axis versus the percentage remaining at

4,000 kilometers on the y-axis. 

lives in water are represented by the different

lines (color-coded) on the graph. 

representative oceanic current speeds are

marked on the table (from Klecka et al., 2000;

Leonard et al., 1997; Brown, 1991; Ross, 1978,

1982). 

use Figure 9-6, representing a substance with a

0 2 5 7 8 9 10 11 12

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Days Since Release

Proportion Remaining

Half-life - days

5

4

3

2

1

Figure 9-4. Proportion of a POPs release remaining for

various atmospheric half-lives.

Figure 9-5. Oceanic surface current speeds (NOAA).

Lower atmoThis is consistent with the use

Figure 9-5 proAs discussed in ChapAverage oceanic surface water speeds

Certain oceanic currents can

Rivers generally move at

Figure 9-6 again sets the necessary

Different halfExamples of

Point X provides an example of how to

1 3 4 6
Addition of Chemicals 

Figure 9-6. Water transport model. 

half-life in water of 2 months, caught in the Gulf 

Stream. After 2,500 miles transport at ~1 knot, 

30% of the original release would remain. Further informing the evaluation of a pertinent halflife criterion in water is the approximate 1/40 

ratio for wind speed to oceanic surface current 

(UK Ministry of Defense, 1973). These analyses 

are consistent with the Stockholm Convention 

half-life criterion in water of 2 months (under 

Annex D, 1(a)), but are clearly highly dependent 

on which waterbody and current are under consideration. 

Beyond these first-order transport comparisons, a 

number of multimedia environmental fate and 

transport models have undergone recent development (Klecka et al., 2000). It is anticipated that 

these or similar models may be used to satisfy 

the Stockholm Convention long-range environmental transport modeling requirements. Multimedia models are necessary because POPs distribute to, and move between, air, soil, water, 

and sediment media. To adequately understand 

the fate and transport of POPs in the environment, it is necessary to know how they will disperse among these media, all of which exhibit 

different degradation rates and abilities to act as 

storage reservoirs or transport media. 

An example of such a multimedia model related 

to the 12 priority POPs is provided by Scheringer 

et al. (2000), and replicated here in Figure 9-7. 

In this graph, the x-axis represents total persistence in the environment; the y-axis shows spatial range normalized to the Earth’s circumference. Total persistence is the weighted average 

of residence times in all the media, a method of 

merging persistence values in different media 

into a single figure. The spatial range is the 

distance a chemical could theoretically travel in 

the model before reaching a predetermined cutoff level. From this graph, it is evident that 

distance traveled is not linearly related to total 

environmental persistence. This lack of linearity 

is due to differences in the strengths of binding 

to immobile particles in soil or sediment. This is 

combined with the fundamental link between 

transport distance and the half-life in the transport medium, which sets a maximum possible 

distance function irrespective of degradation 

rates in soil or sediment. A similar modeling 

analysis by Rodan et al. (1999) confirmed the 

potential for the 12 priority POPs to travel long 

distances. It is important to note that these 

models only compare the relative distance traveled by chemicals. This is because the termination decision used for model concentration and 

9-9

Addition of Chemicals


Figure 9-7. Spatial range R (normalized to the earth’s 

circumference) and persistence τ of various chemicals 

based on results of the global model proposed by 

Scheringer (1996). 1: hexachlorobenzene, 

2: hexachlorobiphenyl, 3: mirex, 4: endrin, 5: DDT, 

6: toxaphene, 7: chlordane, 8: dieldrin, 9: TCDD, 

10: aldrin, 11: heptachlor, 12: lindane. See Scheringer et 

al. (2000) for a more detailed interpretation of this plot. 

Source: With permission, Wiley-VCH, ACS. 

distance is arbitrary yet consistent; i.e., when is 

the environmental concentration low enough to 

conclude that the chemical is gone and the distance calculation should cease? 

Adverse Effects/Toxicity 

Toxicity is perhaps the most difficult criterion to 

quantify in the screening process because it 

inherently encompasses considerations of dose, 

the complexity of which is best dealt with at the 

risk profile stage. Merely finding a chemical at 

extremely small levels with modern laboratory 

equipment cannot be considered a prima facie 

case for toxic risks. This caution must be balanced against the technical limitations of toxicology and ecotoxicology to detect and quantitate 

subtle adverse effects and the need to not await 

the demonstration of overt toxicity in remote 

locations before action is taken—a precautionary 

approach. Guidance on how to resolve this dilemma, and achieve a balance between providing information at the screening stage versus the 

more detailed risk profile, is best found by analyzing the text of the Stockholm Convention 

(Annex D.1.(e) & D.2): 

D. 1. ... (e) Adverse effects: 

(i) Evidence of adverse effects to human health 

or to the environment that justifies 

consideration of the chemical within the scope 

of this Convention; or 

(ii) Toxicity or ecotoxicity data that indicate 

the potential for damage to human health or 

to the environment. 

2. The proposing Party shall provide a 

statement of the reasons for concern including, 

where possible, a comparison of toxicity or 

ecotoxicity data with detected or predicted 

levels of a chemical resulting or anticipated 

from its long-range environmental transport.... 

Here, negotiators anticipated a hierarchy of 

toxicity evidence, with priority to be given at the 

screening stage to actual “evidence of adverse 

effects,” justifying consideration in this global 

Convention. The adverse effects screening criterion can also be fulfilled with “data that indicate 

the potential for damage,” again emphasizing 

the need for data—not speculation—but not at 

the expense of awaiting irreversible harm. The 

criterion category is then followed by a statement 

of concern (Annex D.2) at the screening stage, in 

which the proponent Party is to include, where 

possible, a comparison of data with detected or 

predicted levels. These efforts to provide quantitative information on adverse effects—measured 

or predicted—are to be further elaborated upon 

and evaluated by the POPRC in the risk profile 

stage (below). 

A wide variety of human health and ecotoxicity 

data are anticipated under this criterion. For 

human health, numerous national and international expert scientific bodies assess data to 

determine if a hazard exists to humans. Many of 

these bodies develop standards considered protective of health. The EPA reference dose, for 

example, is an estimate of a daily exposure to 

9-10

Addition of Chemicals 

the human population (including sensitive subgroups) that is likely to be without an appreciable 

risk of deleterious effects during a lifetime 

(www.epa.gov/iris). The U.S. Agency for Toxic 

Substances and Disease Registry (ATSDR) develops Minimal Risk Levels (MRLs) for many environmental contaminants (www.atsdr.cdc.gov). 

Internationally, the WHO and International 

Agency for Research on Cancer (IARC) are central to developing health standards. Reliance on 

all of these standards should, however, be tempered by an understanding of how they are derived, the use of uncertainty factors and public 

health protective assumptions that reduce numerical values below the actual research data 

findings, and details and differences in the specific wording of the standards (e.g., tolerable 

versus minimal risk versus safe). Ultimately, an 

expert appraisal, including analysis of the primary published literature, should be undertaken 

to fully inform deliberations. 

For ecotoxicity, a similar process of problem formulation is undertaken to identify stressors and the 

animals and plants at risk. Quantitative data for 

chemical stressors can come in the form of dose 

estimates related to toxic endpoints or as tissue 

levels associated with adverse effects. Ideally, 

laboratory studies of toxic doses will include the 

tissue levels associated with these effects, but this is 

not always the case. The complexity of ecotoxicity 

data is accentuated by species differences, interaction with the species’ ambient environment, multiple simultaneous stressors, and difficulties in determining low levels of toxicity, especially in field 

situations (Beyer et al., 1996). Expert judgment 

is again essential in exercising appropriate caution in determining the potential for adverse 

effects. 

The Risk Profile 

The risk profile is central to the ultimate determination of whether a substance is a POP warranting action under the Stockholm Convention. 

The emphasis on a detailed scientific review and 

expert judgment is paramount in recommendations by scientific bodies (Klecka et al., 2000; 

CEG, 1998). The complexity of the detailed risk 

profile can appear, however, somewhat contrary 

to a more straightforward application of numerical screening criteria, with its expeditious, yet 

possibly inaccurate, clarity. With this in mind, it 

merits emphasis that passing the screening 

phase of the addition of chemicals process does 

not necessarily imply that a chemical will be 

listed as a POP. This determination can only be 

made after a critical review and analysis of all 

the pertinent data. As stated in Annex E of the 

Stockholm Convention: 

The purpose of the review is to evaluate 

whether the chemical is likely, as a result of its 

long-range environmental transport, to lead to 

significant adverse human health and/or 

environmental effects, such that global action 

is warranted. 

The information requirements for the risk profile 

include elaboration and review of the Annex D 

(screening criteria) information, supplemented by 

Annex E information on sources, hazards, environmental fate and models, measured levels, and national and international assessments and status. 

The profile will be prepared by the POPRC, with 

data input from Parties and observers (e.g., industry, nongovernmental, and intergovernmental 

organizations). It is recognized that more detailed 

initial submission packages by proponent Parties 

covering these points will expedite the process. 

Risk Management Options 

After a determination is made by the POPRC that 

a substance is likely to be a chemical warranting 

global action, information is then obtained on 

Annex F management options and socioeconomic considerations. A clear separation is 

considered important between the risk profile 

and management stages so that potential implementation considerations do not affect the scientific evaluation of whether a substance warrants 

consideration under the Stockholm Convention. 

After such a determination is made, however, 

Annex F explicitly requires consideration of technical and socioeconomic factors in determining 

the best course(s) of action in dealing with a 

chemical. To facilitate such decisions by the 

9-11

Addition of Chemicals


COP, the report on management options by the 

POPRC will review the efficacy and efficiency of 

possible control measures, alternative products 

and processes, impacts on society of implementing possible control measures, waste and disposal 

implications, and additional factors influencing 

the ability of Parties to implement obligations. 

The Decision 

The ultimate decision to list a chemical in the 

annexes and on appropriate control strategies 

rests with the Conference of the Parties. This 

decision must give due consideration to, but is 

not bound by, the recommendations of the 

POPRC in the risk profile and management 

report. In doing so, the Stockholm Covention 

seeks to maximize the input of scientific information from multiple sources (intergovernmental, 

government, industry, nongovernment organizations) into a transparent decision making process. Consistent with standards maintained 

during the negotiation of the Stockholm Convention, decisions by the COP are to be reached by 

consensus. Absent such consensus, a 3/4 majority vote is necessary to add a chemical. Changes 

to the information requirements and criteria in 

Annexes D (screening), E (risk profile), and F 

(risk management/socioeconomics) can be made 

only by consensus, to maintain a consistent standard for evaluating proposals to add chemicals. 

The Future 

During the May 2001 signing ceremony for the 

POPs Convention in Stockholm, Sweden, agreement was reached to commence work on defining the structure and process for the POPRC. 

Proposal dossiers for the addition of chemicals 

may be pursued on a national basis in anticipation of entry into force of the Convention and 

commencement of POPRC review functions, but 

chemicals cannot be added in the interim. The 

particular approach used by the POPRC and 

COP to review and consider the first chemicals 

for addition following entry into force will yield 

valuable information on how the process will be 

implemented in the future. 

References 

Beyer WN, Heinz GH, Redmon-Norwood AW, eds. 

1996. Environmental contaminants in wildlife: Interpreting tissue concentrations. SETAC Special Publications 

Series. Boca Raton, FL: CRC Press, Lewis Publishers. 

Brown J. 1991. The final voyage of Rapaiti: A measure 

of sea-surface drift velocity in relation to the surface 

wind. Marine Pollut Bull 22(1):37-40. 

CEG. 1998. Report of the first session of the Criteria 

Expert Group for Persistent Organic Pollutants. 

Bangkok, Thailand, 30 October 1998. UNEP/POPS/ 

INC/CEG/1/3. http://irptc.unep.ch/pops/CEG-1/ 

CEG1-3.htm. 

Chemical Manufacturers Association (CMA). 1996. PTB 

[persistent, toxic, bioaccumulative] Policy Implementation 

Guidance. Product Risk Management Guidance for 

PTBs. Arlington, VA: CMA. February 1996. 

Draxler RR, Dietz R, Lagomarsino RK, Start G. 1991. 

Atmos Environ 25A(12):2815–2836. 

Canada TSMP. 1995. Toxic Substances Management 

Policy. Persistence and Bioaccumulation Criteria. Government of Canada, Environment Canada. No. En 40-

499/2-1995E. June 1995. 

Klecka G, Boethling B, Franklin J, Grady L, Graham D, 

Howard PH, Kannan K, Larson RJ, Mackay D, Muir D, 

van de Meent D, eds. 2000. Evaluation of Persistence 

and Long-Range Transport of Organic Chemicals in the 

Environment. Pensacola, FL: SETAC Press. 

International Joint Commission (IJC). 1993. A Strategy 

for the Virtual Elimination of Persistent Toxic Substances. 

Vol. 1. Report of the Virtual Elimination Task Force to 

the International Joint Commission. Windsor, Ontario, 

Canada. 

Isnard P, Lambert S. 1988. Estimating bioconcentration 

factors from octanol-water partition coefficient and 

aqueous solubility. Chemosphere 17(1):21–34. 

Leonard KS, McCubbin D, Brown J, Bonfield R, Brooks 

T. 1997. Distribution of Technetium-99 in UK coastal 

waters. Marine Pollut Bull 34(8):628–636. 

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Mason LR, Bohlin JB. 1995. Optimization of an atmospheric radionuclide monitoring network for verification 

of the Comprehensive Test Ban Treaty: U.S. Advanced 

Research Projects Agency/Pacific-Sierra Research Corporation Arlington, VA: PSR Report 2585. 

NAAEC. 1998. Process for Identifying Candidate Substances for Regional Action under the Sound Management of Chemicals Initiative: Report to the North American Working Group on the Sound Management of 

Chemicals by the Task Force on Criteria. Montreal, 

Canada: Commission for Environmental Cooperation 

under the North American Agreement on Environmental 

Cooperation. 

Rodan BD, Pennington DW, Eckley N, Boethling RS. 

1999. Screening for persistent organic pollutants: 

techniques to provide a scientific basis for POPs criteria 

in international negotiations. Environ Sci Technol 

33:3482–3488. 

Ross DA. 1978. Opportunities and Uses of the Ocean. 

New York: Springer-Verlag. 

Ross DA. 1982. Introduction to Oceanography. 

Prentice-Hall, Inc. 

Scheringer M. 1996. Persistence and spatial range 

endpoints of an exposure-based assessment of organic 

chemicals. Environ Sci Technol 30:1652-1659. 

Scheringer M, Bennett DH, McKone TE, Hungerbuhler 

K. 2000. Relationship between persistence and spatial 

range of environmental chemicals. In: Lipnick RL, 

Mackay D, Jansson B, Petreas M, eds. Persistent 

Bioaccumulative Toxic Chemicals: Fate and Exposure. 

Washington, DC: American Chemical Society. 

UK Ministry of Defense. 1973. Hydrographic Department. Series NP 136. Ocean Passages for the World, 

3rd Ed., Suppl. No. 1. Taunton, UK. 

UNECE-LRTAP. 1998. United Nations Economic 

Commission for Europe. Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution on 

Persistent Organic Pollutants. 24 June, 1998; Aarhus, 

Denmark. http://www.unece.org/env/lrtap/. 

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

1995. Great Lakes Water Quality Initiative Technical 

Support Document for the Procedure to Determine 

Bioaccumulation Factors. Office of Water. EPA-820-B95-005. 

U.S. EPA. 1998. Proposed category for persistent, 

bioaccumulative, and toxic chemicals. 

FR63(192):53417–53423. October 5, 1998. 

9-13

Appendix A Transport Pathways 

Figures showing transport pathways traversed by 

air masses en route to 11 sites within the United 

States are provided in this Appendix. The figures 

and the calculations on which these figures are 

based were produced by the Center for Air Pollution Impact and Trends Analysis (CAPITA) at Washington University in St. Louis, MO, and can be 

found at http://capita.wustl.edu. 

The figures are based on the calculation of several 

thousand trajectories calculated backwards for 10 

days at 2-hour intervals from each of the receptor 

sites for the year 1999. The different color shading in the figures refers to the probability that 

trajectories passed over a given area before arriving 

at the receptor site. The boundaries of each 

shaded region represent lines of constant probability. The areas shaded in red have the highest 

probability of being traversed by trajectories, 

whereas those shaded in light blue have lower 

probability. To obtain a truly representative 

picture of the average transport pathways, in the 

same way that climatological statistics are obtained, these calculations would need to be repeated for several years. Further details regarding the calculations can be found in Husar and 

Schichtel (2001). 

A-1

Appendix


1. Aleutian Islands, AK 

July 

April 

October 

January 

1. Aleutian Islands, AK 

July 

April 

October 

January 

A-2

Appendix 

2. Point Barrow, AK 

July 

April 

October 

January 

2. Point Barrow, AK 

July 

April 

October 

January 

A-3

Appendix


5. Seattle, WA 

July 

April 

October 

January 

6. San Francisco, CA 

July 

April 

October 

January 

A-4

Appendix 

9. San Diego, CA 

July 

April 

October 

January 

10. Big Bend, TX 

July 

April 

October 

January 

A-5

Appendix


11. N. Minnesota, MN 

July 

April 

October 

January 

12. St. Louis, MO 

July 

April 

October 

January 

A-6

Appendix 

13. Everglades, FL 

July 

April 

October 

January 

14. Rochester, NY 

July 

April 

October 

January 

A-7

Appendix


15. Burlington, VT 

July 

April 

October 

January 

Reference Final report of Cooperative research agreement 

Husar RBH, Schichtel B. 2001. Ozone and PM air CX825834. Accessible through http:// 

quality analyses in support of public needs: Visualization capita.wustl.edu/capita/capitareports/POPs/ 

of transboundary air pollutant transport to the US. TransportclimatologyJP.ppt. 

A-8