Health Advisories for Consumers of Great Lakes Sport Fish: Is the Message

Being Received?

John Tilden,1 Lawrence P. Hanrahan,2 Henry Anderson,2 Charles Palit,3 Joseph Olson,2 William Mac Kenzie,1 and

the Great Lakes Sport Fish Consortium

1Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta GA 30333 USA; 2Bureau of Public Health, Wisconsin

Division of Health, Madison, WI 53703 USA; 3Wisconsin Survey Research Laboratory, University of Wisconsin, Madison, WI 53703 USA

Nationwide, 45 states issue health advisories for sport fish consumers. Ch cal coninnts in

some Great Iakes (GL) sport fish include compounds suspeted of causing advese reproductve

and developmental effects. Although advisories to reduce consumption of contaminated fish,

espeially by women, have been issued by GL states (.e., Illinois, Indiana, Mich n, Minnesota,

New York, Ohio, Penyani, and Wison) ce the mid-1970., l i about adsory awarness and GL sport fish cons pionin the general population. To estimate the prevalence of GL sport fish ptio an health advisory awarenes, we otd a pulationbased teephone survey of 8,306 adult residents of the eight GL ste We information

concerning respondents' d a fish consumption during the pgreeding

year, and sport fish coadvisory aw nss. The se was 69%. GL

sport fish were eaten during the p iyear by 8A4% [95%c i id 9.2]

of adults in the GL sates, tely 4.7 million persons. Wo n a 439% (CI,

39.4-48.4) of consumers. Alhouh 49.9% of GL sport fish cse of a health

advisory, awareness varied significanty by se 58.2% (CI, 51.7-64.7) of males and 39.1% (CI,

32.645.6) of females were aware. Using logistic regrsion, we found awaree associated with

male sex [odds ratio (OR) =2.3; CI, 1.5-3.5), white race (OR - 4.2; CI, 1.9-9.1), college degree

(OR = 3.1; CI, 1.3-7.6), and couns i 224 GL sport fish meals/year (OR - 2.4; CI, 1.4-4.3).

Only half of GL sport fish coum reported aness of a health advisry ning tg

GL sport fish. Awarns was ep l low ng women, s the need ofae risk

communication prga f f le . I work e G health

adsories, Illinois, Indi , Mihi i New r Oo ion-based

random-Jigit-dial svy s t fish i

Environ Healh Perpn10 3 (199T hap/.Iehks ihsi.ge:

Great Lakes (GL) sport fish consumption

advisories were first issued in the 1970s after

extensive testing detected chemical contaminants in fish tissue. Of particular concern

were environmentally persistent lipophilic

pollutants such as polychlorinated biphenyls

(PCBs) and DDT. These compounds are

often found in the highest concentrations in

the older and larger predatory fish, which are

sought and preferred by many sport anglers.

In 1991, an estimated 2.55 million

licensed anglers fished on one or more of the

Great Lakes (1). Thus, the popularity of this

sport presents a significant potential for

human exposure to chemical residues in fish

tissue. Although two decades of environmental regulation have substantially reduced

chemical residues (2-3), some sport fish still

contain levels thought to be potentially

harmful to human health (Anderson et al.,

unpublished data).

Studies of long-term consumption of GL

sport fish confirmed an association between

contaminated fish consumption and increased

PCB or DDT\DDE body burdens (47).

The potential adverse health effects of these

contaminants have been studied extensively

(8-10). The EPA has classified PCBs and

DDT\DDE as probable human carcinogens.

Consistent with low exposure effects

observed in nonhuman primates, some

human epidemiologic studies have found

associations between maternal/fetal PCB

levels, Lake Michigan sport fish consumption, and adverse reproductive and developmental effects (11-13). These studies are

not conclusive, however, and scientists disagree regarding interpretation of their findings (14-17). This level of uncertainty

complicates the process of communicating

risk information to sport fish consumers.

Current GL sport fish consumption

advisories seek to 1) inform the public

about the chemical contaminants contained

in some sport fish, 2) educate consumers as

to how they can minimize their exposure to

contaminants, 3) remind consumers of the

health benefits of fish consumption (18,19),

and 4) present advisory information in a

manner conducive to maximal voluntary

compliance (Anderson et al., unpublished

data). Because of potential adverse reproductive and developmental effects, all current advisories make specific consumption

frequency recommendations for women of

childbearing age. GL advisories seek to help

individual consumers make informed decisions regarding sport fish consumption.

In the GL states, the level of advisory

awareness among licensed anglers has been

used to assess the adequacy of advisory communication programs (20). Licensed anglers

are a relatively easy-to-identify group of GL

sport fish consumers who can be surveyed by

mail (5,21-22). One drawback of this

approach is that the results of surveys conducted solely on anglers with fishing licenses

might not be generalizable to all persons who

eat GL sport fish. To overcome this limitation, we conducted a random-digit-dial telephone survey of the general population. We

surveyed adult residents of the eight GL

states to characterize the types of fish eaten

by the general population, the demographic

characteristics of persons who ate GL sport

fish, and the level of advisory.awareness

among these GL sport fish consumers.

Materials and Methods

Survey design. From April 1993 through

February 1994, trained interviewers from

the University of Wisconsin Survey Research

Laboratory conducted a population-based

random-digit-dialed telephone survey

(23-25) of adults (i.e., persons >18 years of

age) residing in Indiana, Illinois, Michigan,

Minnesota, New York, Ohio, Pennsylvania,

and Wisconsin). One randomly selected

adult from each participating household was

interviewed. Interview dates were scheduled

so that approximately equal numbers of

interviews were completed during each of

the four seasons. Informed consent was

obtained before the start of the interview,

and the data acquisition procedures maintained complete respondent anonymity.

Interviewers used a standard questionnaire to collect information regarding demographic characteristics, the types of fish eaten

Address correspondence to L.P. Hanrahan, Bureau

of Public Health, Wisconsin Division of Health,

Room 138, 1414 E. Washington Avenue, Madison,

WI 53703 USA.

The Great Lakes Sport Fish Consortium includes

James Boddy, Marvin Budd, Mandy Burkett, Claire

Falk, Beth Fiore, Grace Lee, Bob Johnson, Marty

Kanarek, Susan Monaghan, Dan Reed, Tracy Shelley,

William Sonzogni, Greg Steele, and Dollis Wright.

This work is a result of research sponsored by the

U.S. Public Health Service, Agency for Toxic

Substances and Disease Registry under grant

75/ATH598322-03.

Received 11 February 1997, accepted 2 September

1997.

1360 Volume 105, Number 12, December 1997 * Environmental Health Perspectives
Articles * Awareness of sport fish health advisories

during the preceding 12 months, and an

estimate of the average number of fish meals

eaten during a time interval selected by

respondents (e.g., during a week, month, or

year). Respondents were characterized as

persons who either 1) ate no fish, 2) ate

only commercially purchased fish, 3) ate

sport fish not caught in a Great Lake, or 4)

ate some GL sport fish. Respondents who

reported eating GL sport fish provided additional information, including estimates of

the number of GL sport fish meals they

consumed during the preceding 12 months,

whether they had heard of their state's

health advisory for sport fish consumers,

and if they had followed specific advisory

recommendations (e.g., cleaning and cooking practices). They provided consumption

estimates for six GL sport fish groups: lake

trout, carp/catfish, brown trout, rainbow

trout/chinook salmon/coho salmon,

perch/smelt/walleye, and all other GL sport

fish. These fish species were grouped

according to the level of chemical contaminants reported by federal and state monitoring programs. These groups are listed in

approximate rank-order, from highest to

lowest, by level of chemical contaminants

detected. We defined advisory awareness as

a self-report of having heard of the health

advisory. Compliance was defined as a selfreport of always or usually following an

advisory recommendation. None of the selfreported information was independently

verified.

Analytic methods. We calculated overall

and state-specific response rates using standard procedures (26) (see Appendix 1). To

obtain population-based estimates, we

weighted each respondent's information

(27,28). Appendix 2 describes the case

weighting methodology.

The low number of respondents with less

than a high school degree was insufficient to

weight separately; thus, only two categories of

educational attainment were used to calculate

weights. These categories were persons with a

high school degree or less and persons with at

least some post-high school education. In all

analyses, respondent age was coded as a threelevel categorical variable (i.e., 18-34 years,

35-44 years, and 45 or more years of age)

based on the likelihood of childbearing. We

initially explored the data through univariate

and stratified analysis. Using SUDAAN statistical software (Research Triangle Institute,

Research Triangle Park, NC) (29), we calculated overall prevalence estimates for four different fish consumption patterns, advisory

awareness among GL sport fish consumers,

and self-reported compliance among GL

sport fish consumers who reported advisory

awareness. We conducted a stratified analysis

to determine how advisory awareness varied

by sociodemographic group and we conducted a multivariable logistic regression analysis

(30). Possible interactive effects between sex

and other variables were assessed. Models of

significant variables were derived by a backward model-selection method (31) and by

comparison of hierarchical models using likelihood ratio chi-square statistics. Age group

and state of residence variables were kept in

all models. To adjust for the study's sampling

design, the final logistic regression analysis

used SUDAAN software.

Results

A total of 8,306 persons were interviewed,

including over 1,000 adult residents per state.

The overall survey response rate was 69% (see

Appendix 1). State-specific response rates

ranged from 57% in New York to 78% in

Wisconsin. Persons who had less than a high

school degree were underrepresented, comprising 14% of our weighted sample compared with the 23% indicated by the 1990

census for these states (28).

Fish consumption. The estimated percentages of persons in the eight GL states

who ate fish obtained from different sources

are shown in Table 1. The median number

of total fish meals eaten (from all sources)

was not significantly different between

groups. An estimated 8.4% [95% confidence interval (CI), 7.6-9.2] of adult residents in the GL states had eaten GL sport

fish during the preceding year (approximately 4.7 million persons). Ninety-two

percent of GL sport fish consumers in this

survey were white, the median age was 39

years, 44% were women, and 52% lived in

either Michigan or Ohio. Results of the

1990 census indicates that, among adult residents of the GL states, 84% were white,

53% were women, and 26% lived in either

Michigan or Ohio.

The estimated distribution of GL sport

fish consumers by fish consumption level

and sex is shown in Figure 1. A median of

6.5 fish meals were eaten per year (range,

1-292 fish meals per year). We estimated

that 830,000 persons in the eight GL states

had eaten .24 GL sport fish meals per year.

Men reported having eaten GL sport fish

more frequently than did women. The

median consumption levels for men and

women were 8.2 (CI, 6.7-9.6)] and 5.8 (CI,

5.0-7.6) meals, respectively.

The median number of GL sport fish

meals reportedly consumed by whites and

nonwhites were 6.4 (CI, 5.8-7.2) and 9.8

(CI, 6.1-18.8), respectively. This difference

was not statistically significant because of

Table 1. Estimated prevalence and frequency of consumption by adult residents of Great Lakes states", by

type of fish consumed during the preceding year (1993-1994)

Percent Median

Sample estimated fish mealsb

Type of fish consumed size prevalence eaten/year Cl

Ate commercial fish only 4,825 61.3 33.6 32.4-36.0

Ate non-GLsportfish 1702 18.3 34.8 31.2-37.2

Did not eatfish 872 12.0 -

Ate GLsportfish 679 8.4 34.8 31.2-38.4

Total 8,078c 100.0 28.8 27.6-30.0

Abbreviations: GL, Great Lakes; Cl, 95% confidence interval.

alllinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin.

bFish of all types.

clnformation missing for 228 of 8,306 survey respondents.

12

10

0~

a

8

6

4

<5.0 5-11 >35

Figure 1. Number of Great Lakes sport fish consumers by consumption level and sex in eight Great Lakes

states (Indiana, Illinois, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin) from April

1993 to February 1994).

aSport fish caught in the Great Lakes.

Environmental Health Perspectives * Volume 105, Number 1Z December 1997

12-23

Sport fish meals8 per year

1361
Articles * Tilden et al.

the small number (n = 50) of nonwhite GL

sport-caught fish eaters in our unweighted

sample.

The GL sport fish group eaten by the

greatest number of respondents was

perch/smelt/walleye (n = 500) followed by

rainbow trout/chinook salmon/coho salmon

(n = 316), lake trout (n = 254), other GL

sport fish (n = 162), brown trout (n = 73),

and carp/catfish (n = 64).

Sport fish consumption advisory

awareness. The prevalence of advisory

awareness among adult GL sport fish consumers by various sociodemographic characteristics is shown in Table 2. Approximately

half of all GL sport fish eaters reported that

they had heard of their state's health advisory. Advisory awareness varied significantly by

race, sex, educational attainment, GL sportcaught fish consumption level, and state of

residence. Advisory awareness was not significandy different by age category. Our sample

contained small numbers of GL sport fish

eaters from some states. This resulted in

unstable state-specific estimates of advisory

awareness as indicated by wide 95% confidence intervals. In Minnesota and New York,

the level of awareness indicated by the

weighted sample was approximately 10% less

than that indicated by the unweighted data.

In these states, persons with relatively high

weighting (e.g., males 18-34 years of age

who did not have a high school degree) tended to report that they had not heard of the

advisory.

The final logistic regression model for

variables associated with advisory awareness

among GL sport fish eaters is shown in

Table 3. The risk estimates displayed in

Table 3 are odds ratios (OR). In the analysis, Wisconsin was used as the referent

group in the logistic regression model

because the level of GL sport fish consumption and advisory awareness among

Wisconsin anglers had been documented

previously. Statistical significance (p<0.05)

was assessed by 95% confidence intervals.

Parameters with confidence intervals that

Table 2. Prevalence of advisory awarenessa among adults who had eaten sport fish caught from the

Great Lakes by sociodemographic characteristicsb April 1993-February 1994

Percent

prevalence

Sample advisory

Characteristic size awareness Cl

Total 671 49.9 45.2-54.6

Age (years)

18-34 215 46.9 38.7-55.1

35-44 188 56.1 47.9-64.3

>45 268 49.2 41.8-56.6

Racec

White 618 52.1 47.2-57.0

Other 50 22.1 9.4-34.8

Sex

Male 347 58.2 51.7-64.7

Female 324 39.1 32.6-45.6

Educational attainment

<High school degree 49 33.7 17.6-49.8

High school graduate 272 47.9 40.5-55.3

Some college 189 49.9 41.1-58.7

College graduate 161 61.7 52.9-70.5

GLSCF consumption leveld

<6 fish meals/year 291 44.7 37.5-52.0

6-23.9 fish meals/year 256 50.4 42.8-58.0

>24 fish meals/year 122 62.4 52.4-72.4

State of residence

Michigan 184 60.3 52.7-67.9

Ohio 135 37.9 28.9-46.9

Wisconsin 92 65.3 53.7-76.9

Minnesota 67 37.5e 24.4-50.6

Illinois 57 51.3 36.8-65.8

Indiana 50 42.0 26.7-57.3

Pennsylvania 44 47.8 31.3-64.3

New York 42 50.2e 32.2-68.2

Abbreviations: Cl, 95% confidence interval; GLSCF, Great Lakes sport-caught fish.

aAwareness defined as having heard of the sport fish advisory; 8 of 679 consumers had missing information on advisory awareness.

bPrevalence estimates based on analysis of weighted data using SUDAAN software (Research Triangle

Institute, Research Triangle Park, NC).

cThree individuals missing race information.

dTwo individuals were missing GLSCF consumption level information.

eThis weighted estimate is unstable, being 10% less than the estimate derived from unweighted data.

did not include an OR of 1.0 were therefore

the ones that were significant. After adjusting for other variables in the model, advisory awareness was significantly associated

with male sex, white race, having a college

degree, and eating .24 GL sport fish meals

per year. GL sport fish consumers in Ohio

were significantly less likely than GL sport

fish eaters in Wisconsin (the referent state)

to be aware of an advisory. None of the

interaction terms investigated were statistically significant.

Of those GL sport fish consumers who

were aware of an advisory, compliance with

advisory recommendations differed significantly between men and women (Table 4).

Use of recommended cleaning and cooking

methods was the most frequently reported

risk reduction practice, reported by 69% of

men and 55% of women. Compliance was

significantly lower for advisory recommendations that required changes in fishing

Table 3. Multivariable logistic regression modela

for advisory awarenessb among adult Great Lakes

states residents who had eaten sport fish caught

in the Great Lakes during the preceding 12 months

(telephone survey dates: April 1993-February

1994)

Characteristic Odds Ratio Cl

Age (years)

18-34 Reference

35-44 1.6 0.9-2.6

.45 1.3 0.8-2.1

Race

Other Reference

White 4.2 1.9-9.1

Sex

Female Reference

Male 2.3 1.5-3.5

Education

<High School Reference

High school graduate 1.7 0.7-4.0

Some college 1.8 0.8-4.3

College graduate 3.1 1.3-7.6

GL sport fish

consumption level

<6 fish meals/year Reference

6-23.9 fish meals/year 1.3 0.8-2.1

>24 fish meals/year 2.4 1.4-4.3

State of residence

Wisconsin Reference

Illinois 0.5 0.2-1.2

Indiana 0.5 0.2-1.1

Michigan 0.9 0.5-1.6

Minnesota 0.5 0.2-1.0

New York 0.7 0.3-1.7

Ohio 0.4 0.2-0.7

Pennsylvania 0.7 0.3-1.7

Abbreviations: Cl, 95% confidence interval; GL,

Great Lakes.

aModel includes 666 out of the 671 total persons

for whom complete data was known for all variables in the model; three persons had missing

race information and two persons had missing

GLSCF consumption level information (see also

Table 2 for category frequencies).

bAwareness is defined as having heard of the

sport fish advisory.

1 362 Volume 105, Number 12, December 1997 * Environmental Health Perspectives
Articles - Awareness of sport fish health advisories

behavior (e.g., changing fishing locations to

catch fish with lower levels of chemical contamination).

Discussion

The popularity of sport fishing on the Great

Lakes is indicated by our estimate that

approximately 4.7 million persons had eaten

GL sport fish during the year preceding the

survey. Our results indicate that the majority

of these persons infrequently ate GL sport fish

and that they tended to eat fish species that

contain relatively low contaminant levels (i.e.,

perch/smelt/walleye). The GL sport fish consumption levels reported by most respondents

were highly unlikely to result in body burden

levels previously associated with adverse

human health effects. However, the frequency

of GL sport fish consumption varied widely,

suggesting substantially different potentials

for chemical contaminant exposure among

individual consumers. Because environmentally persistent chemical contaminants are

present in some GL sport fish, consumers will

probably continue to seek information

regarding the risks and benefits of eating GL

sport fish.

In the United States, state governments

are primarily responsible for managing

potential risks associated with contaminants

in locally caught sport fish (32). As of

September 1993, 45 of the 50 states had

issued one or more fish or shellfish consumption advisories or bans (33). Each of the eight

GL states has issued sport fish consumption

advisories since the mid-1970s. The overall

effectiveness of sport fish advisory programs

depends on the effectiveness of both the recommendations made and communication

methods used (21,34,35). Unfortunately,

inconsistency between state-issued advisories

has been recognized as a nationwide problem

(32). Inconsistencies in GL sport fish advisories have at times confused consumers and

limited the effectiveness of advisories in the

region. Representatives of the eight GL states

have drafted a uniform advisory for the

Great Lakes (Anderson et al., unpublished

data), but it has not yet been adopted. In

this survey, although ability to make interstate comparisons was limited, state of residence predicted the level of advisory awareness, suggesting that significant differences in

advisory programs continue to exist.

In general, GL sport fish advisories

encourage sport fish consumers to eat fewer of

the fish species and sizes known to contain elevated levels of chemical contaminants and recommend the use of cleaning and cooking

methods that can substantially reduce the levels of PCBs and other fat-soluble contaminants contained in a fish meal [Anderson et

al., unpublished data; (36-38)]. Since GL

advisories were first issued, several studies have

documented a decline in GL sport fish consumption (22,39,40). In our survey, the most

widely accepted advisory recommendation was

deaning and cooking methods. The results of

a survey of New York anglers indicated that

the use of these cleaning and cooking methods

was significantly higher among persons who

were aware of that state's health advisory (21).

These findings support the belief that sport

fish consumption advisories can decrease

chemical contaminant exposures among sport

fish consumers if effective communication

programs are used.

Communication programs in the GL

states have traditionally targeted licensed

anglers, who are predominantly white men.

Written advisory information (e.g., fishing

regulation booklets and advisory brochures)

has usually been distributed through the

recreational fishing industry and governmental offices. GL sport fish consumers who do

not purchase licenses might not have access

to information distributed in this way.

Because we did not ask respondents if they

had purchased fishing licenses, we could not

directly assess advisory awareness among

licensed anglers and nonlicensed GL sport

fish consumers. However, our estimated

number of GL sport fish consumers was

roughly twice that of the most recent estimate of licensed GL anglers, suggesting that

a substantial proportion of GL sport fish

consumers were not licensed anglers. Only

half of the adults in our population-based

Table 4. Self-reported compliance with health advisory recommendations by sex of consumers of Great

Lakes sport fisha who had heard of the advisory

Percentage following recommendations

Men Women

Area of recommendation Percent Cl Percent Cl

Cleaning and cooking methods 68.8 61.5-76.5 54.6 44.6-64.6

Consumption frequency 50.1 41.9-58.3 42.8 33.0-52.6

Fish species and size 50.3 42.1-58.5 29.4 20.4-38.4

Fishing locations 43.6 35.6-51.6 28.2 19.1-37.2

Cl, 95% confidence interval.

aAdult residents of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin

who reported eating Great Lakes sport fish during the year preceding their interview (survey dates were

April 1993-February 1994).

survey who had eaten GL sport fish had

heard of their state's health advisory. When

contrasted with the overall high levels of

advisory awareness found by previous mail

surveys of licensed GL anglers (7,21,22), it

appears that substantial numbers of nonanglers are not receiving advisory messages.

Our survey results indicate that existing

advisory communication programs are less

effectively reaching women, nonwhites, and

persons with lower levels of educational

attainment. The results of previous surveys

of licensed GL anglers also support this conclusion (21,225. Well-accepted principles of

risk communication indicate that messages

designed for specific audiences are often

needed to reach diverse subgroups within a

population (41,42). The weight of evidence

from the risk communication literature, surveys of licensed GL anglers, and this population-based survey of GL sport fish consumers suggests that expanded use of targeted advisory communication methods are

needed.

To accomplish this, the EPA has developed a detailed and comprehensive guidance document (42) to assist health professionals with the task of fish consumption

advisory risk communication. The manual

provides specific advice to health professionals on all aspects of health advisory risk

communication, including risk communication as a process of sharing information,

problem analysis and program objectives,

audience identification and needs assessment, communication strategy design and

implementation, program evaluation, and

methods of responding to public inquiries.

By following the principles outlined in the

EPA guidance, state jurisdictions can develop successful risk communication programs

for those who have not been receiving this

very important message.

In an era of shrinking governmental

budgets, individual state agencies must balance the costs of managing potential health

risks against the magnitude of the potential

health risk. It is unlikely that sport fish advisory programs will have sufficient resources

to mount extensive communication campaigns. However, targeted communication

programs designed to reach specific groups

are possible. Our results suggest that additional communication efforts are particularly needed to reach persons most sensitive to

the effects of the chemical contaminants

(i.e., women of childbearing age). Greater

collaboration between government agencies

and risk communication specialists would

probably reduce the costs of developing and

evaluating new communication programs,

and this collaboration would reap the additional benefit of increased consistency

among state-issued advisories.

Environmental Health Perspectives * Volume 105, Number 12, December 1997 1 363
Articles * Tilden et al.

Appendix 1'

........... ......;i;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.. ... .. ... RnaI sempi. ...coe .. .......

e., Kriwm fowm1I ...: .

hj tWt oreke ds. tic p r. tedy .rt_i .......... ....... nu.be

g, Known eligible nonresponse all!

h. Complete inteviwte.el

The.CASRO response ratef.oa ..

.h

(g.+.h. h + b...+.e gI)' `d+f)

State April iPa uly t ..................1. u.a,y O erl

il.i.nois 6;...... 4% 66 69% 67 7

Michigan 65% 66% 73% 76% . 70%. Minnesota 73% 7% 7% 83 7%

NewYork 51% .53%.. 61% 6 57%

Ohio 66% 68% 76% ~74% 71

Pennsylvania 60% 56% 74% 74% c7%

Weconsin 79%. --.?79% .%.

Tota ..61% 61%. 6I9 70% 69%

.Appendix 2

To obtain population-basedestimates gwe w.eigted..ach by he. i.v .r.. the probabily of h s thesate response ktatee

the number adults residing i andthe quantiy sof tele-

,~~~~~~~~~~~ : W . .~~~~~~~~~. 1199. eamS."..... A.M.1.0

wereusedtoweight each stasdo the population ag.e,.

sex. en duca.tional a.ttainmet ......... distibutio (72.... .

T:hus standard tlephone w metos were used in the

sdyl(22i. Th'e comput onot finl weiht for each observation is

described in the following eqiations.

F_W= DWx PSWx 0.25,

.where FW= final weight, DW= desgn weight and PSW= poststratifica-

*tio weight

..~~~~~~ ~ ~ ~~~~~~~ ISE-c. DWSS..R.R x lISP x NRP)/10. x...... NAN), .. .:. !k . ..:.

W.hr S.8 =satepecificeop rate ;ercent:,, HP.IS,P husehold unit

selctonpobbil ityNR.P= ubroeieta phones in the house.holdd

unit, and NAH= number ofadultsinth hu hold unit..

~~~.0 u

where CPC= state-specific census population in the statification cell and

-DW= sum of the design weights. for te completed sample cases in the

...stratification cell.

.The final weight is a product oft deign w.eig9ht and ithe poststratification

weight, and the constant.25. The :const-anintcluded so that all four

p.li waves could be ud estima annual prevalence>.Thedesign!wei.ghtis constructed front thesotat specific responsp:..

rate, the hou.shold unit..selectio.npr obiliy,eInumber of resiea

p.hones inthe household u eheume of ts residing in the

Polteiiain& atI.v c hFu r constr tJreclco mbinatio

of. eighsats three age ou i, w sexi rdtwoeducaion groups.

Deinwegt were su nndwrtehbsnainitth statificatio

*... cetas1* serve the tenor in stern. The lSSc ur..i population estimate was

obtaRined for each ataifie io tLThsl_cistatiiato th. weight was

the ratio of the census populatin eimtes to the sum of the desin

weights in each statification cell.

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National Security Education Program

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Environmental Health Perspectives * Volume 105, Number 12, December 1997 1365