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The Texas Natural Resource Conservation Commission (TNRCC) requested that the TexasDepartment of Health (TDH) evaluate potential health risks associated with consumption of fish andcrabs taken from West Galveston Bay. This request resulted from the detection of mercury in watersamples taken as part of TNRCC's routine monitoring of water bodies near industrial areas (303(d)list).

Galveston Bay is Texas' largest and most important estuarine source of seafood, generating nearlyone billion dollars per year in commercial and recreational harvests. The bay accounts forapproximately one third of the state's commercial fishing income and over one-half of the state'sexpenditures for recreational fishing. Nearly 300,000 licensed recreational anglers spend some twomillion hours sport-fishing on the bay annually. More than three million people live in the fivecoastal counties bordering the Galveston Bay system with 20 percent of the population living withintwo miles of the Bay or its tidal tributaries. The Upper Galveston Bay system is home to one of thenation's largest petrochemical and industrial complexes. As a result, the Bay receives treatedwastewater from more than 1,400 industrial and municipal point source discharges that amount tomore than 60% of the wastewater (by volume) discharged in Texas. It also receives non-pointsource pollutants in storm water runoff generated by agricultural, urban, suburban and rural landusers within the Bay. The Brazoria National Wildlife Refuge is located along the mainland of WestGalveston Bay. Galveston Island, with a population of about 60,000 comprises the southernshoreline.

In response to TNRCC's request, TDH collected and analyzed fish and crab samples from four siteswithin West Galveston Bay in May 1999. The study area encompasses all of West Galveston Bayfrom the Galveston Causeway to San Luis Pass. Thirty-two fish samples, consisting of seven spottedtrout, seven southern flounder, six black drum, seven sheepshead, four Atlantic croaker, one reddrum, and eight blue crab composite samples were analyzed for metals, polychlorinated biphenyls(PCBs), pesticides, and semi-volatile and volatile organic compounds (VOCs).

The organic compounds detected in fish and crab samples from West Galveston Bay aresummarized in Table 1. Pyridine was found in all eight crab samples and at low levels in three fishsamples. Low levels of the pesticide chlordane were found in a few samples. Metals detected inthese samples included cadmium, copper, lead, mercury, selenium, and zinc.



Deriving Health-based Assessment Comparison Values (HACs)

TDH screened the chemical contaminants found in the fish and crabs from West Bay for furtherconsideration by comparing the average concentration of each contaminant to health-basedassessment comparison (HAC) values for non-cancer and cancer endpoints. We used the U.S.Environmental Protection Agency's (EPA's) reference doses (RfDs) or the Agency for ToxicSubstances and Disease Registry's (ATSDR) minimal risk levels (MRLs) to derive the noncancerHAC values. RfDs and MRLs are estimates of daily exposures to contaminants that are unlikely tocause adverse noncancer health effects even if exposure occurs for a lifetime. The cancer riskcomparison values that we used in this consultation are based on EPA's chemical-specific cancerslope factors, an estimated excess lifetime risk of one cancer in ten thousand (1 x 10-4) exposedpeople, and an exposure period of 30 years. TDH used standard assumptions for body weight (70kilograms, adult; 35 kilograms, child) and fish consumption (30 grams per day, adult; 15 grams per day, child) to calculate the HAC values [1].

Addressing the Potential for Cumulative Effects

When multiple chemicals affect the same target organ or when several chemicals present in seafoodtissues are carcinogens, we assume that adverse effects are additive. To evaluate the potential publichealth impact of additive noncancerous health effects, we calculate the number of meals per weekneeded to exceed a hazard index (HI) of one (1.0). The HI is the sum of the ratios of the estimatedexposure doses for each contaminant divided by its respective RfD (or MRL). A hazard index ofless than one suggests that exposure to the combined contaminants, at the specified exposure levels,is unlikely to cause adverse noncancer health effects, even if exposure continues for many years. While a hazard index that is greater than one does not necessarily mean that exposure to thecontaminants will result in adverse health effects, it does suggest that some public healthintervention should be considered. To estimate the potential excess lifetime cancer risk associatedwith multiple carcinogens, we calculate a cumulative risk by adding the estimated risk associatedwith each of the contaminants. For carcinogenic chemicals, the Texas Department of Healthrecommends that consumption of fish contaminated with carcinogenic chemicals be limited toamounts that result in an estimated excess theoretical lifetime cancer risk of less than 1 in 10,000 persons exposed to one or more contaminants in seafood.

Addressing the Unique Vulnerabilities of Children

TDH, EPA and ATSDR recognize that the unique vulnerabilities of infants and children demandspecial attention. For several reasons, children have a special vulnerability to some toxic substances. Children are smaller than adults, for instance, resulting in higher doses of chemical exposure per unitof body weight. Their body systems are still developing, making them less able than adults tometabolize, detoxify, and excrete some toxic substances. Children's developing body systems cansustain permanent damage if toxic exposures occur during critical growth stages. Consequently,children who consume seafood contaminated with toxic chemicals may be at greater risk for toxiceffects than adults. Therefore, in accordance with ATSDR's Child Health Initiative [2] and theEPA's National Agenda to Protect Children's Health from Environmental Threats [3], weevaluated the potential public health hazards to children who eat fish or crabs from West Galveston Bay.

Risk Characterization

Assessing noncancer health effects

With the exception of the pyridine found in crabs, all the contaminants were found at averageconcentrations below their respective noncancer HAC values (Table 1). The Texas Department ofHealth laboratory investigated the origin of pyridine found in crab tissues and concluded thatpyridine is a naturally-occurring component of crab tissue [4]. Pyridine in crabs does not appear tobe the result of, or related to, environmental contamination and does not constitute a hazard tohuman health. Based on the contaminants that were found in the fish and crab samples, there were no additive noncancer effects for us to evaluate.

Assessing cancer health effects

All the contaminants found in the fish and crabs were found at average concentrations below theirrespective cancer HAC values (Table 1). Chlordane is classified as a probable human carcinogen(Group B2) based on an increase in the incidence of tumors in laboratory animals [5]. Based onpreviously-stated assumptions, we estimated that people eating one meal per week of fish and crabsfrom West Galveston Bay for 30 years would increase their theoretical excess lifetime cancer risk byapproximately 3 in 10,000,000 persons exposed. Qualitatively, we interpret this to be aninsignificant increase in the lifetime risk for development of cancer.


The Texas Department of Health has established criteria for issuing fish consumption advisoriesthat are based on EPA guidelines [1]. If long-term consumption of one meal per week could havean adverse impact on human health, the Seafood Safety Division recommends that theCommissioner of Health issue an advisory. Based on the findings of this health consultation, we have determined that:

  1. The contaminants measured in samples of fish and crabs from West Galveston Bay pose no apparent public health hazard because regular consumption of this seafood would be unlikely to have an adverse impact on human health.

  2. Fish and crabs from West Galveston Bay may be consumed by the general public withoutrestriction.


TDH will review future fish and crab tissue data from West Galveston Bay as this information becomes available.

Table 1.

Contaminant Concentrations in Fish from West Galveston Bay (mg/kg)
Chemical Number Affected/Number Sampled Average Concentration
Comparison Value Basis for Comparison Value
Pesticides (mg/kg)
chlordane 9/40 0.0036
EPA chronic oral RfD: 0.0005 mg/kg/day
ATSDR chronic oral MRL: 0.0006 mg/kg/day
EPA slope factor: 0.35 (mg/kg/day)-1
Semi-volatile Organic Compounds (mg/kg)
pyridine-crabs 8/8 11.2
2.3 EPA chronic oral RfD: 0.001 mg/kg/ day
pyridine-finfish 3/32 0.138
pyridine-all samples 11/40 2.3
Metals (mg/kg)
cadmium 20/40 0.015
0.47 ATSDR chronic oral MRL: 0.0002 mg/kg/day
copper 17/40 1.53
-------- None Available
lead 17/40 0.0136
-------- IEUBK3
mercury 14/40 0.078
0.7 ATSDR chronic oral MRL: 0.0003 mg/kg/day
selenium 40/40 0.58
12 EPA chronic oral RfD/ATSDR chronic oral MRL: 0 .005 mg/kg/day
Zinc 40/40 10.7
700 EPA chronic oral RfD: 0.3 mg/kg/day
1 Assumes 70 kg adult ingesting 30 grams of fish and crabs per day (one eight-ounce meal per week) and, for carcinogenicity risk, an acceptable risk level of 1 x 10-4 for a lifetime of exposure
2 Not detected at concentrations above laboratory reporting limit
3 Integrated Exposure Uptake Biokinetic Model


  1. Environmental Protection Agency 1997. Guidance for assessing chemical contaminant datafor use in fish advisories. Volume II. Fish Sampling and Analysis, 2nd Edition. Office ofScience and Technology, Office of Water, U.S. Environmental Protection Agency,Washington, DC.

  2. Agency for Toxic Substances and Disease Registry (ATSDR), Office of Children's Health. 1995. Child Health Initiative.

  3. Environmental Protection Agency (EPA), 1998. The Children's Environmental HealthYearbook.

  4. Fest, G, Villanacci, J, Ward, J, Williams, L et al., 2000. Assessment of the toxicologicalsignificance of pyridine in crabs from water bodies in Texas. 2000. Texas Department ofHealth, unpublished communications.

  5. IRIS. Integrated Risk Information System, September 2000. Environmental ProtectionAgency, Office of Research and Development, National Center for EnvironmentalAssessment.


Jerry Ann Ward, Ph.D.
Seafood Safety Division
Bureau of Food and Drug Safety

Eric Fonken, D.V.M.
Environmental Resource Specialist
Seafood Safety Division
Bureau of Food and Drug Safety

Lisa Williams, M.S.
Environmental Epidemiology and Toxicology Division

John F. Villanacci, Ph.D.
Environmental Epidemiology and Toxicology Division


George Pettigrew, P.E.
Senior Regional Representative
ATSDR - Region 6


Alan W. Yarbrough
Environmental Health Scientist
Division of Health Assessment and Consultation
Superfund Site Assessment Branch
State Programs Section


This West Galveston Bay Health Consultation was prepared by the Texas Department of Healthunder a cooperative agreement with the Agency for Toxic Substances and Disease Registry(ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was initiated.

Alan W. Yarbrough
Technical Project Officer, SPS, SSAB, DHAC, ATSDR

The Division of Health Assessment and Consultation, ATSDR, has reviewed this health consultation and concurs with its findings.

Richard Gillig
Chief, State Programs Section, SSAB, DHAC, ATSDR

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