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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 Upper Galveston Bay. This request resulted from the detection of mercury inwater samples taken as part of TNRCC's routine monitoring, placing this portion of the GalvestonBay estuary system onto the EPA's 303(d) list. Currently, the upper portion of Galveston Bay andthe Houston Ship Channel are under a fish consumption advisory issued in 1990 due tocontamination of catfish and crabs with dioxins. Seafood samples analyzed from the advisory areain 1994 and 1996 indicated that catfish and crabs from the advisory area were still contaminatedwith dioxins. Samples collected in 1999 for the present evaluation were collected within theadvisory area but were not analyzed for dioxins.

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. Annually, nearly 300,000 licensed recreational anglers spendsome two million hours sport fishing on the bay. More than three million people live in the fivecoastal counties bordering the Galveston Bay system; twenty percent of those people live within twomiles 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 area.

In February 1999, TDH collected and analyzed fish and crab samples from four sites in UpperGalveston Bay: ten each from Morgan's Point, the Houston Yacht Club, Sylvan Beach, and themouth of Little Cedar Bayou. These forty samples, consisting of seven black drum, three red drum,eight sheepshead, three southern flounder, eight spotted sea trout, one sand sea trout, two stripedbass, and eight composite blue crabs, were analyzed for metals, polychlorinated biphenyls (PCBs),pesticides, and semivolatile (SVOCs) and volatile organic compounds (VOCs). Funding for thisproject was provided through a grant from the TNRCC.

The organic compounds detected in fish and crab samples from Upper Galveston Bay aresummarized in Table 1. Semivolatile and volatile compounds, including pyridine, diethyl phthalate, bis(2-ethylhexyl)phthalate, benzene, toluene, and acetone were detected at very low levels and inonly a few samples. Pyridine was found only in crab samples. Low levels of the pesticideschlordane, heptachlor epoxide, DDD, DDE, dieldrin, hexaclorobenzene, lindane, and dacthal werefound in a few samples. Aroclor 1260 was detected in three samples. Metals detected in these samples include cadmium, copper, lead, mercury, selenium, and zinc (Table 2).


Deriving Health-based Assessment Comparison Values (HACs)

TDH screened the chemical contaminants found in the fish and crabs from Upper Galveston Bay forfurther consideration 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) personsexposed to the contaminants, and an exposure period of 30 years. TDH used standard assumptionsfor body weight (70 kilograms, 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. The Texas Department of Health recommends limiting consumptionof fish contaminated with carcinogenic chemicals to amounts that result in an estimated excesstheoretical lifetime cancer risk of less than 1 in 10,000 persons exposed to those contaminants inseafood.

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 susceptibility to some toxicsubstances. Children are smaller than adults, which results in higher doses of chemical exposure perunit of body weight. Their body systems are still developing, making them less able than adults tometabolize, detoxify or excrete some substances, and they may be more likely to absorb specifictoxicants. Children's developing body systems can sustain permanent damage if toxic exposuresoccur during critical growth stages. Children may be more prone to developing certain cancers as aresult of chemical exposures than adults. Consequently, children who consume seafoodcontaminated with toxic chemicals may be at greater risk for toxic effects than adults. Therefore, inaccordance with ATSDR's Child Health Initiative [2] and the EPA's National Agenda to ProtectChildren's Health from Environmental Threats [3], we evaluated the potential public healthhazards to children who eat fish from Upper Galveston Bay.

Characterizing Risk

Assessing Noncancer Health Effects

Individually, average concentrations of the contaminants in the fish and crabs from Upper GalvestonBay were found at levels below their respective noncancer HAC values (Tables 1 and 2). TDHinvestigated the origin of pyridine found in crab tissues from this water body 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. Eight of the chlorinated hydrocarbonpesticides (chlordane, dacthal, DDD, DDE, dieldrin, heptachlor epoxide, hexachlorobenzene, andlindane) detected in fish from Upper Galveston Bay are known to have adverse non-cancerouseffects on the livers of experimental animals [5]. The HI for the combinations of contaminantsobserved in samples from this water body was less than one (1.0).

Assessing Cancer Health Effects

The individual contaminants in fish and crabs from Upper Galveston Bay were found at averageconcentrations below their respective cancer HAC values (Table 1). Seven of the chemicals(chlordane, DDE, DDD, dieldrin, heptachlor expoxide, hexachlorobenzene, and bis(2-ethylhexyl)phthalate) found in fish from the bay are classified by the EPA as probable humancarcinogens (Group B2) based on an increase in the incidence of tumors in laboratory animals [5]. Benzene is classified by the EPA as a known human (Group A) carcinogen, based onepidemiological evidence [5]. People who eat fish from the bay may be exposed to several of thesecontaminants at the same time. Using EPA's chemical-specific cancer slope factors and the averageconcentration for each of the compounds, we calculated that eating one eight-ounce meal per weekof finfish other than catfish from the bay that contain average concentrations of all the observedcontaminants (an unlikely scenario) for 30 years could theoretically increase excess lifetime cancerrisk by approximately one excess cancer in 34,483 exposed persons. Qualitatively, we interpreted this as low increased risk of contracting cancer during a lifetime.


  1. Consuming finfish other than catfish from Upper Galveston Bay poses no apparent publichealth hazard. Long-term ingestion of more than one meal per week of finfish, excluding catfish, would be unlikely to have an adverse impact on human health.

  2. Catfish and blue crabs from Upper Galveston Bay are currently under a fish consumption advisory issued in 1990 due to contamination with dioxins. Based on the data available for this report, we were not able to re-evaluate the existing catfish and blue crab advisory.


The TDH Seafood Safety Division has established criteria for issuing fish consumption advisoriesbased on recommendations from the EPA [1]. If long-term consumption of one meal per week couldhave an adverse impact on human health, the Seafood Safety Division recommends that theCommissioner of Health issue a consumption advisory. Based on the above conclusions, werecommend:

  1. The existing advisory recommending that blue crabs and catfish from Upper Galveston Bay not be consumed should remain in effect.

  2. The public may consume finfish other than catfish from Upper Galveston Bay withoutrestriction.

  3. TDH should monitor finfish and blue crab data from Upper Galveston Bay as thisinformation becomes available. Analysis of dioxins should be included in any monitoringactivities.

Table 1.

Organic Contaminant Concentrations (mg/kg) in Fish and Crabs from Upper Galveston Bay
Chemical # Affected/
# Sampled
Average Concentration (Range) Comparison Value1 Basis for Comparison Value
Pesticides (mg/kg)
chlordane 20/40 0.37
1.2 EPA chronic oral RfD: 0.0005 mg/kg/day
1.4 ATSDR chronic oral MRL: 0.0006 mg/kg/day
1.6 EPA slope factor: 0.35 (mg/kg/day)-1
dacthal 1/40 0.0001
23 EPA chronic oral RfD: 0.01 mg/kg/day
DDD 5/40 0.0017
1.2 EPA chronic oral RfD for DDT: 0.0005 mg/kg/day
1.6 EPA slope factor : 0.24 (mg/kg/day)-1
DDE 15/40 0.0073
1.2 EPA chronic oral RfD for DDT: 0.0005 mg/kg/day
1.6 EPA chronic oral slope factor 0.34 (mg/kg/day)-1
dieldrin 3/40 0.0006
0.12 EPA/ATSDR chronic oral RfD/MRL 0.00005 mg/kg/day
0.03 EPA slope factor 16 (mg/kg/day)-1
heptachlor expoxide 10/40 0.0017
0.03 EPA chronic oral RfD 0.000013 mg/kg/day
0.06 EPA slope factor 9.1 (mg/kg/day)-1
hexachlorobenzene 5/40 0.0005
1.9 EPA chronic oral RfD 0.0008 mg/kg/day
0.047 ATSDR chronic oral MRL 0.00002 mg/kg/day
0.34 EPA slope factor 1.6 (mg/kg/day)-1
lindane 2/40 0.0001
0.7 EPA chronic oral RfD 0.0003 mg/kg/day
Semivolatile Organic Compounds (mg/kg)
1/40 0.05
46.7 EPA chronic oral RfD: 0.02 mg/kg/day
38.8 EPA slope factor: 0.014 (mg/kg/day)-1
diethyl phthalate 1/40 0.035
1,866 EPA chronic oral RfD: 0.8 mg/kg/day
pyridine 6/8 (crabs only) 0.33
2.3 EPA chronic oral RfD: 0.03 mg/kg/day
Volatile Organic Compounds (mg/kg)
acetone 7/40 0.048
233 EPA chronic oral RfD: 0.1 mg/kg/day
benzene 1/40 0.0003
9.9 EPA slope factor: 0.055 (mg/kg/day)-1
toluene 1/40 0.0003
466 EPA chronic oral RfD: 0.2 mg/kg/day
Polychlorinated biphenyls (mg/kg)
Aroclor 1260 3/40 0.006
0.047 EPA/ATSDR chronic oral RfD/MRL-Aroclor 1254: 0.00002 mg/kg/day
0.271 EPA slope factor 2 (mg/kg/day)-1
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

Table 2.

Inorganic Contaminant Concentrations (mg/kg) in Fish and Crabs From Upper Galveston Bay
Chemical # Affected/
# Sampled
Average Concentration (Range) Comparison Value1 Basis for Comparison Value
cadmium 11/40 0.016
0.47 ATSDR chronic oral MR:L 0.0002 mg/kg/day
copper 34/40 1.7
-------- none available
lead 2/40 0.0017
-------- IEUBK3
mercury 18/40 0.057
0.7 ATSDR chronic oral MRL: 0.0003 mg/kg/day
selenium 40/40 0.92
12 ATSDR/EPA chronic oral MRL/RfD: 0.005 mg/kg/day
zinc 40/40 10.2
700 ATSDR/EPA chronic oral MRL/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)
2 not detected at concentrations above laboratory reporting limit
3 Integrated Exposure Uptake Biokinetic Model, EPA


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

  2. Agency for Toxic Substances and Disease Registry. Child health initiative. Office ofChildren's Health. Washington: U S Department of Health and Human Services; 1995.

  3. U S Environmental Protection Agency. The Children's Environmental Health Yearbook.Washington: US Environmental Protection Agency; 1998.

  4. Fest G, Villanacci J, Ward J, Williams L et al. Assessment of the source of pyridine in crabs from water bodies in Texas. Austin: Texas Department of Health (in preparation).

  5. IRIS. Integrated Risk Information System. Environmental Protection Agency, Office ofResearch and Development, National Center for Environmental Assessment. September,2000. Available from: URL:


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

Susan Bush, B.S.
Natural Resource Specialist
Seafood Safety Division
Bureau of Food and Drug Safety

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

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

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


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 Upper 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

Table of Contents The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

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