## Public Health Assessments & Health Consultations

Page last reviewed: October 16, 2009 Page last updated: October 16, 2009 Content source: Agency for Toxic Substances and Disease Registry

Agency for Toxic Substances and Dise ase Registry, 4770 Buford Hwy NE, Atlanta, GA 30341 Contact CDC: 800-232-46 36 / TTY: 888-232-6348 HEALTH CONSULTATION

WELSH RESERVOIR MOUNT PLEASANT, TITUS COUNTY, TEXAS

Se ptember 30, 1998

Pre p ared b y

: Texas Department of Health Under Cooperative Agreement with the Ag enc y

for Toxic Substances and Disease Re g

istr y

TABLE OF CONTENTS

BACKGROUND AND STATEMENT OF ISSUES

DISCUSSION

A

TSDR's CHILD HEALTH INITIATIVE

CONCLUSIONS

RECOMMENDATIONS

REFERENCES

PREPARERS OF REPORT

CERTIFICATION

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## Public Health Assessments & Health Consultations

HEALTH CONSULTATION

WELSH RESERVOIR MOUNT PLEASANT, TITUS COUNTY, TEXAS

BACKGROUND AND STATEMENT OF ISSUES
The Texas Department of Health Seafood Safety Division (SSD) reques ted that the Health Risk Assessment and Toxicology Program re evaluate the current advisory limiting consumption of fish taken from Welsh Reservoir, a 1,365 acre cooling reserv oir for Welsh Power Plant and operated by Southwestern Electric Power Comp any (SWEPCO). Welsh Reservoir is located 11 miles so utheast of Mount Pleasant in Ti tus County, Texas. During the late 1970's, several power plant cooling reservoi rs in Texas received discharges from ash ponds containing elevated seleni um levels, resulting in increa sed selenium concentrations in fish. An investigation of a series of fish kills in waterbodies near power plants in the early 1980's implicated elevated levels of selenium in fish tissue and wate r. The Texas Parks and Wildlife Department (TPWD) reported levels of selenium in Welsh Reservoir fish ranging from 2.28 to 4.41 ppm from 1986-1989.

Since the fish kills, the Te xas Department of Health (T DH), TPWD, and SWEPCO have worked cooperatively to monitor selenium levels in fish ti ssue. In 1992, TDH issued a fish consumption advisory for the rese rvoir after it was dete rmined that the levels of selenium in fish could pose a potential he alth risk. The advisory recomm ended that adults consume no more than one eight-ounce meal each week and children seven ye ars of age and older consume no more than one four -ounce meal each week. Childr en six and under, pregnant women, or women who may soon become pregna nt were advised not to consume the fish. Additionally, persons consumin g fish from the re servoir were advised not to consume mineral dietary supplements with selenium exceedin g 50 micrograms per day.

In 1998, TDH collected 20 fish (12 largemouth bass, 6 channe l catfish, 1 flathead catfish, and 1 common carp) for a re-evaluation of the present fish consumption advisory. The concentration of selenium in the fish ranged from 1.2 to 4.5 ppm with an overall average concentration of 2.7 ppm (Table 1). Selenium le vels in fish from Wels h Reservoir continue to be above reported national averages (0.1 to 1.5 ppm [1]). The average concentration of selenium in fish from Welsh Reservoir ranged between 2.2 and 4.4 ppm from 1986 to 1989 (Figure 1). There is no clear in dication of an overall change in selenium con centrations in fish tissue over the 12 years of investigation; however, ther e is a 9 year peri od (1989-1998) in which there are no data to represent an overall increase or decrease in average concentrations. The maximum average concentrati on of 4.4 ppm seleni um in fish tissue occurred in 1987.

Table 1. Selenium in Welsh Reservoir Fish
November 1996 Pa g e 1 of 7 ATSD R -PHA-HC-Welsh Reservoi r -p1

10/7/2010 htt p ://www.atsdr.cdc. g ov/hac/ p ha/ p ha.as p ?docid=145& pg =1Species # collected Size Selenium Range (ppm) Selenium Average (ppm) February 1998 Largemouth Bass 12 18 - 20" 1.87 - 3.88 2.97

Channel Catfish 6 18 - 23.5" 1.2 - 2.44 1.78

Flathead Catfish 1 28" 2.78 2.78 Common Carp 1 24" 4.5 4.5
All Fish 2.7

DISCUSSION

Selenium
Selenium is a naturally occurring substance that is widely, but unevenly distributed in rocks and soils of the earth's crust. It is rarely found in pure form in the environment. When rocks decompose into soils, selenium often combines with sodium and oxygen to form sodium selenate, or with water to form sodium selenite, both of which are water soluble. Plants easily take up inorganic selenium compounds from water and change them to organic selenium compounds such as selenometh ionine. The major man-made source of selenium in the environment is coal burning, es pecially the fly ash that resu lts from burning coal. Persons living near industrial sites may be exposed thro ugh ingesting the soil or water, breathing the dust, eating plants that may ha ve taken up selenium from soil , or ingesting fish that may have taken up selenium fr om high concentrations in water [2]. The estimated bioaccumulation factor for selenium in fish ranges from 485 to 1,746, depending on the species [3]. In general the more soluble and mobile forms of se lenium (selenit e and selenate) dominate under aerobic (high oxygen concentrati ons) and alkaline (hig h pH) conditions [2].
Humans and animals are both capable of absorb ing and utilizing both organic or inorganic forms of selenium from food or water sources. Most of the selenium that ente rs the body is excreted in the urine within 24 hours. Selenium can build up in the body if exposure is high and occurs over a long period of time. Body burdens of selenium primarily occur in the liver, kidneys, hair, and nails. Sele nium is an essential dietar y element for both human and animals in either the inorganic or organic form . Selenium has antioxid ant effects which help Pa g e 2 of 7 ATSD R -PHA-HC-Welsh Reservoi r -p1

10/7/2010 htt p ://www.atsdr.cdc. g ov/hac/ p ha/ p ha.as p ?docid=145& pg =1prevent damage to tissue s caused by oxygen. A selenium deficient diet can result in Keshan disease, the signs and sympto ms of which may include mu scle pain, cardiomyopathy, enlargement of the heart, increased red blood cell fragility, and pancreatic degeneration.

The human recommended daily allowance (RDA) of seleni um for maintenance of good health is 55 micrograms per day (ug/day) fo r women and 70 micrograms per day for men. Estimates of the average intake of selenium from food for the U.S. population range from 71 to 152 micrograms of selenium per person per day [2]. Welsh et al. reported that about three percent of Maryland residents consumed diets which contained over 200 Âμg of selenium per day [4]. The Food and Nutr ition Board of the National Re search Council has estimated the safe and adequate daily diet ary intake of selenium in adul ts to be 50 to 200 Âμg [5]. However, when eaten in amounts that are not mu ch higher than required for good nutrition, selenium becomes harmful to humans and animals [2] (Figur e 2). Signs and symptoms of sub-acute and chronic toxicity in humans include brittleness and loss of hair and nails; blisters, eruptions and skin mottling; pitting and excessive decay of the te eth; a garlic or sour -milk breath odor; periodic episodes of na usea and vomiting; and increasing fatigue.
No human populations in the U. S. have been reported to ha ve chronic sele nium toxicity, including populations in the we stern part of the country with naturally high levels of selenium in the soil and water. In a study of 142 subjects livi ng in a seleniferous area of South Dakota and Wyoming, ther e was no evidence of toxicity from selenium in subjects whose intake was as high as 724 ug per day [6 ]. There have been a limited number of case reports of individuals who deve loped minimal signs of selenium toxicity following chronic dietary intakes of 850-900 ug per day. In area s of China with selenium intakes of 3,200 to 6,690 ug per day, clinically apparent selenium toxicity wa s observed, while persons with daily intakes in the range of 42 -750 ug per day did no t produce any signs of toxicity or other adverse health effects [7].
The Agency for Toxic Substances and Disease Registry (ATSDR) recent ly has established a chronic oral Minimum Risk Level (MRL) for selenium of 5 Âμg/kg /day [1]. For a 70 kg adult this is equivalent to an intake of 350 Âμg/day. The MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without apprecia ble risk of noncancer health effects over a specifie d duration of exposure. The MRL was derived from a study involving a Chinese population with high se lenium intake. Blood se lenium concentrations and degree of selenosis were de termined for 349 adults. The en dpoint used to derive the MRL was nail disease, specifically brittlen ess of nails. By regression analysis the corresponding selenium dietary intakes were determined. A "no observ able adverse effects level" (NOAEL) of 15 ug/kg/da y, was determined. The NOAEL is the highest dose at which no statistically or biologically significant adverse effects were ob served. For a 70 kg adult this dose is equivalent to a selenium intake of 1,050 Âμg/day. To establish the MRL, ATSDR divided the NOAEL by a factor of three to account for human vari ability. It is important to note that the MRL based on the Chinese study may be conse rvative because only dietary exposure was considered and it has been sugges ted that inhalation exposure to selenium in smoke was significant. The population studie d cooked their meals on open fires of coal containing high concentrations of selenium.
Carcinogenicity
The EPA and the National Toxicology Program have determined that selenium is not classifiable as a carcinogen and it is rated as a Group D chemical. In fact, studies of cancer in humans suggest that lower than normal selenium levels in the diet may increase the risk of Pa g e 3 of 7 ATSD R -PHA-HC-Welsh Reservoi r -p1

10/7/2010 htt p ://www.atsdr.cdc. g ov/hac/ p ha/ p ha.as p ?docid=145& pg =1cancer. This may be due to the fa ct that selenium is used in the body in enzymes that protect against oxidative damage to tissues which may be respon sible for cancer promotion. One specific form of selenium, call ed selenium sulfide, is a prob able human carcinogen. Selenium sulfide is not found in foods, and is a very di fferent chemical from th e organic and inorganic selenium commonly found in the environment. Be cause it is not absorbed through the skin, its primary use in the anti -dandruff shampoo Selsun Blue, is considered safe [2].

Toxicological Evaluation In 1992, when TDH estimated th e risks associated with eating selenium contaminated fish, an MRL for this contaminant wa s not available. Using availabl e information, TDH estimated 400 Âμg/day (5.71 Âμg/kg/day assu ming a 70 kg adult) to be a safe and acceptable dietary selenium intake. This estimate d safe daily intake is remark ably similar to the MRL (5 Âμg/kg/day) established by ATSDR and provided approximately a 2.6-fold safety factor below the current NOAEL of 1,050 ug/day, or the lowest level reasonably expected to result in signs or symptoms of toxicity. In perfor ming the risk assessme nt, TDH determined the acceptable daily intake of sele nium from fish by subtractin g an assumed daily intake of selenium from other sources (2 00 Âμg/day [2.86 Âμg/kg/day assu ming a 70 kg adult]) from the estimated safe and acceptable daily intake. Thus, for a 70 kg adult, TDH estimated that 200 Âμg (2.86 Âμg/kg/day) was an acceptable daily intake of se lenium from fish.

To evaluate the current risks associated with ea ting fish from Welsh Re servoir, we used the same paradigm used in the previous risk assessment except th at we used the MRL established by ATSDR. Assuming a background daily intake of seleni um from other sources of 200 Âμg we estimate that approximately 15 0 Âμg/day (2.14 Âμg/kg/d ay assuming a 70 kg adult) is an acceptable daily intake of selenium from fish. Pa g e 4 of 7 ATSD R -PHA-HC-Welsh Reservoi r -p1

10/7/2010 htt p ://www.atsdr.cdc. g ov/hac/ p ha/ p ha.as p ?docid=145& pg =1To determine the actual number of meals that could be consumed without exceeding the MRL, we used two values fo r the concentration term; the arithmetic average and the 95 th percent upper confidence interval (95% UCL) of the arithmet ic average. The 95% UCL is defined as a value that when calculated repe atedly for randomly drawn subsets of site specific data, equals or exce eds the true average 95 percen t of the time. The arithmetic average should be most representative of th e concentration that would be contacted over time; however, the 95% UCL of the average provides a cons ervative estimate of the average concentration and is useful to account for sampling variations and suspected seasonal variations in fish tissue concentrations.
We estimated the 95% UCL by defi ning the distribution of seleni um in fish tissue from Welsh Reservoir using the 1996-97 data and then randomly drawing 1, 000 samples of 20 fish from that distribution. Averages were obtained for each of the 1,0 00 samples and the 950 th

rank ordered average was defined as the 95 th

percentile. Figure 3 provides a graphical representation of the re lationship between the sample dist ribution, the arithmetic average, and the 95% UCL of th e arithmetic average.
Using these assumptions we esti mate that adults (70 kg) co uld eat approximately one and one-half to two (eight ounce) meals per week and children (body weight 10-30 kg) could consume approximately one-half to one and one- half (four ounce) meals per week of Welsh Reservoir fish before exceed ing the MRL (Table 2). Indivi duals would have to consume approximately three times these amounts befo re exceeding the lowest level reasonably expected to result in sign s or symptoms of toxicity.

Table 2. Recommended Limi tations on Long-Term Fish Consumption by body weight

Body Weight Estimates Based on Average and Up per 95% UCL Selenium Levels for the 20 fish samples collected

(kg) (lb) (a) Baseline
exposure (b) Minimum Risk Level Acceptable Daily Intake Quantity of fish that can be consumed without exceeding MRL Pa g e 5 of 7 ATSD R -PHA-HC-Welsh Reservoi r -p1

10/7/2010 htt p ://www.atsdr.cdc. g ov/hac/ p ha/ p ha.as p ?docid=145& pg =1(Âμg/day)

(BW x 2.86 ug/kg/day) (Âμg/day)

(BW x 5 ug/kg/day) of Selenium From Fish (ug/day)
((b) - (a)) Meals per week
Average (2.7 ppm) 95% UCL (3.05 ppm)
Assumes a child body weight and an average meal size of 4 ounces each
10 22 29 50 21 0.5 0.5
20 44 57 100 43 1 0.9
30 66 86 150 64 1.6 1.4 Assumes an adult body weight and an average meal size of 8 ounces each
40 88 114 200 86 1 0.9
50 110 143 250 107 1.3 1.2
60 132 172 300 128 1.6 1.4
70 154 200 350 150 1.9 1.6
80 176 229 400 171 2.1 1.9
90 198 257 450 193 2.4 2.1
100 22 286 500 214 2.6 2.3

ATSDR's CHILD HEALTH INITIATIVE
The TDH has prepared this co nsult under a Cooperative Agre ement with the Agency for Toxic Substances and Disease Registry (A TSDR). TDH has included the following information in accordance with ATSDR's Child Health Initiative.

ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communiti es faced with contamina tion of their water, soil, air, or food. Children are at greater risk than adults from certain kinds of exposures to hazardous substances emitted from waste sites and emergency events. They are more likely to be exposed because they play outdoors and th ey often bring food into contaminated areas. They are shorter than adults, wh ich means they breathe dust, so il, and heavy vapors close to the ground. Children are also smaller, resultin g in higher doses of chemical exposure per body weight. The developing body systems of ch ildren can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identificati on and management decisions, ho using decisions, and access to medical care.
Special consideration was given to children's he alth in this consultation. Children consuming one -half to one and one-half (four ounce) meal s of Welsh Reservoir fi sh per week would not exceed minimal risk levels for adverse health effect s from selenium in fish.

Next Section Table of Contents Pa g e 6 of 7 ATSD R -PHA-HC-Welsh Reservoi r -p1

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Agency for Toxic Substances and Dise ase Registry, 4770 Buford Hwy NE, Atlanta, GA 30341 Contact CDC: 800-232-46 36 / TTY: 888-232-6348 Pa g e 7 of 7 ATSD R -PHA-HC-Welsh Reservoi r -p1

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## Public Health Assessments & Health Consultations

HEALTH CONSULTATION

WELSH RESERVOIR MOUNT PLEASANT, TITUS COUNTY, TEXAS

CONCLUSIONS

There is no clear indication of an overall change in sele nium concentrations in fish tissue over the 12 years of investigation. The maximum average concentration of 4.4 ppm selenium occurred in 1987. The averag e concentration of selenium in Welsh Reservoir fish in 1998 is 2.7 ppm. 1.

Depending on body weight (1 0-30 kg), children could con sume approximately one-half to one and one-half (four ounce) meals of Welsh Reservoir fish per week before exceeding the MRL. Adults (7 0 kg) consuming approximately one and one-half to two (eight ounce) meals of Welsh Reservoir fish per week would not be expected to exceed the MRL. Approximately three times these amounts would be required to exceed the lowest levels reasonably expected to result in signs and symptoms of toxicity, therefore, ingestion of fish at these amounts po se no apparent public health hazard. 2.

RECOMMENDATIONS
The fish consumption advisory issued for Welsh Reservoi r in 1992 should be reevaluated based on the cu rrent recommended limitati ons on long-term fish consumption. 1.

REFERENCES
IRIS, 1998. Integrated Risk Information System. U.S. Environmental Protection Agency, Office of Health an d Environmental Assessment, Environmental Criteria and Assessment Office. Cincinnati, Ohio. 1.

ATSDR, 1996. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Selenium. Atlanta: ATSDR, Aug. 1996. 2.

Lemly, 1985. Toxicology of se lenium in a freshwater re servoir: Implications for environmental hazard evaluati on and safety. Ecotoxicol. En viron. Safety 10:314-338. 3.

Welsh, et al., 1981. Selenium in self-selecte d diets of Maryland re sidents. J. Am. Diet Assoc. 79-277-85. 4.

FNB, NRC, 1980. Food an d Nutrition Board, Nation al Research Council: Recommended dietary allowances, 9th ed. Washington, D.C: National Academy of Sciences. 5. Pa g e 1 of 3 ATSD R -PHA-HC-Welsh Reservoi r -p2

10/7/2010 htt p ://www.atsdr.cdc. g ov/hac/ p ha/ p ha.as p ?docid=145& pg =2Page last reviewed: October 16, 2009 Longnecker, et.al., 1991. Selenium in diet, blood, and toenails in relation to human health in a seleniferous area. Am. J. Clin. Nutr. 53:1288-94. 6.

Yang, et.al., 1983. Endemic se lenium intoxication of humans in China. Am. J. Clin. Nutr. 37:872-81. 7.

PREPARERS OF THE REPORT

Lisa R. Williams, M.S. Toxicologist Health Risk Assessment and Toxicology Program

John F. Villanacci, Ph.D. Director Health Risk Assessment and Toxicology Program

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

ATSDR TECHNICAL PROJECT OFFICER

William Greim Environmental He alth Scientist Division of Health Asse ssment and Co nsultation Superfund Site Assessment Branch

CERTIFICATION

The Welsh Reservoir Health Cons ultation was prepared by the Texas Department of Health under a cooperative agreement wi th the Agency for Toxic Subs tances and Disease Registry (ATSDR). It is in accordance wi th approved methodology and proc edures existing at the time the Health Consulta tion was initiated.

William Greim Technical Project Officer, SPS, SSAB, DHAC

The Division of Health Assessment and Cons ultation, ATSDR, has reviewed this Health Consultation and concurs with its findings.
Richard Gillig Chief, SPS, SSAB, DHAC, ATSDR

Table of Contents Pa g e 2 of 3 ATSD R -PHA-HC-Welsh Reservoi r -p2

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Agency for Toxic Substances and Dise ase Registry, 4770 Buford Hwy NE, Atlanta, GA 30341 Contact CDC: 800-232-46 36 / TTY: 888-232-6348 Pa g e 3 of 3 ATSD R -PHA-HC-Welsh Reservoi r -p2

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