The U.S. Environmental Protection Agency (EPA) Region IV requested the Agency for Toxic Substances and Disease Registry (ATSDR), to review the analytical results of contaminated shellfish (i.e., clams, oysters, shrimp and crabs) samples obtained from Shipyard Creek, North Charleston, South Carolina, and to evaluate the health implications associated with human consumption of shellfish from the creek.

Shipyard Creek is a tributary of Cooper River in North Charleston, South Carolina. The Macalloy Corporation facility is situated on 125 acres at the headwaters of Shipyard Creek. Surface water runoff from the Macalloy facility enters Shipyard Creek. The facility has been operated continuously by various owners since 1941 as a ferro-chrome manufacturing facility. Macalloy Corporation has owned and operated it since 1979. The wastes generated from the facility during the ferro-chrome manufacturing process include the following: chromium; arsenic; lead; barium; manganese; mercury; and zinc.

An ecological study sponsored by the National Oceanic and Atmospheric Administration (NOAA) and EPA was conducted during the summer of 1997. Results revealed the presence of chromium contaminated shellfish and sediments in Shipyard Creek.

The study showed that fish tissue samples were contaminated, but at levels that did not pose a health threat if consumed by humans [1]. The analytical results showed chromium at concentrations that exceed the Food and Drug Administration's (FDA) action levels in edible tissues in 95% of the shrimp, 26% of the blue crabs, and 15% of the oysters tested. Data also showed that shrimp, oysters and crabs contained chromium at concentrations greater than shellfish control samples from other areas outside of Shipyard Creek. The chromium concentrations ranged from 2.7 parts per million (ppm) to 34.3 ppm, 0.14 ppm to 24.3 ppm, and 7.5 ppm to 77.8 ppm, respectively, for eastern oysters, blue crabs, and shrimp from Shipyard Creek (see Attachment 1). The data were analyzed and confirmed by two separate independent statistical tests. The study did not characterize the valence state of chromium in the shellfish. It is assumed, since chromium is normally present in biological systems entirely as chromium III, that the levels reported are for chromium III.

Because of these findings, on April 30, 1998, the South Carolina Department of Environmental and Health Control (SCDEHC)

issued an order pursuant to S.C. Code Annotated 44-1-140, that Shipyard Creek be closed to all harvesting or collecting of shrimp and crab from its mouth to its headwaters. That the existing closure for clams and oysters continue until the SCDEHC revokes the order [1]. The EPA and SCDEHC announced that a Superfund removal at the Macalloy Corporation facility would be performed.

A Superfund removal is a short term clean up action to stabilize or clean up a site that poses an imminent and substantial threat to human health and the environment. The removal will be implemented to mitigate the immediate threat to human health and the environment by preventing site-related releases of contaminated storm water run off from entering into Shipyard Creek and adjacent wetlands. The removal action will consist of building a system of berms and drainage controls designed to collect storm water and the installation of a water treatment system to remove contaminants before discharge [1].

DISCUSSION

At this site, the SCDEHC considered issuing a health advisory based on the amount of shellfish consumed per time period, but ultimately decided to issue a ban on shell fishing from portions of Shipyard Creek. This action was generated by the increased levels of chromium detected in shellfish samples from the 1997 study sponsored by NOAA and EPA. The FDA's levels of concern for chromium contaminated shellfish are: 12 ppm for blue crabs and shrimp, and 13 ppm for oysters. The analytical results of shellfish samples obtained from Shipyard Creek showed that 15% of the oysters, 26% of the crabs, and 95% of the shrimp contained chromium that exceeded FDA's levels of health concern. Furthermore, shellfish samples from Shipyard Creek contained chromium at concentrations greater than chromium levels detected in control shellfish samples from outside of Shipyard Creek. Because the average concentrations of chromium detected in oysters and crabs do not exceed FDA's levels of health concern for chromium, chronic consumption of oysters and crabs probably do not pose a health threat given that biological chromium III is relatively non-toxic. However, because the average concentration of chromium (27 ppm) detected in shrimp is two times the levels of FDA's level of health concern, chronic human consumption of shrimp from Shipyard Creek, may pose a health threat because people may consume chromium III at toxic levels.

The purpose of the Federal Food, Drug and Cosmetic Act (FD&C Act)is to ensure a safe and wholesome food supply. The FD&C and other related statutes, including the Public Health Service Act provide the regulatory framework under which the FDA assesses the effects of environmental contaminants on the safety of consumption of fish and shellfish. The FDA has set levels of concern for chromium contaminated fish and shellfish, and these values were used by SCDEHC to evaluate the health implications associated with exposure to shellfish from Shipyard Creek (see Attachment 1).

The data did not indicate what speciation of chromium was detected in shellfish at this site, however, it is assumed that chromium III was detected because chromium VI is reduced biologically to chromium III. Although in general, chromium III is known to be non-toxic, toxicity depends on the dose, and since shellfish in Shipyard Creek contain chromium at concentrations well above FDA's levels of health concern, there may exist a threat to humans who ingest the shellfish on a frequent basis.

Chromium is a naturally occurring element that is distributed in the air, water, soil, and the earth's crust. The trivalent form and its salts are usually the most stable form of chromium and the main form in plants and animals. At this site, the major route of exposure to chromium is ingestion of contaminated shellfish or gastrointestinal absorption. Chromium VI is more easily absorbed across the GI tract than chromium III, however, chromium VI is reduced biologically to chromium III. The toxicity associated with chromium results primarily from industrial inhalation exposure to chromium VI. Chromium VI compounds are classic skin irritants and sensitivities. Laboratory studies have shown that chromium VI may cause cancer development in mice, at the exposure site, however, these data need to be verified.

CONCLUSION

Chromium concentrations detected in shrimp, but not oysters and crabs, from Shipyard Creek, are a public health hazard; therefore, there may exist a potential health threat after human consumption of the contaminated shrimp on a frequent basis.

RECOMMENDATION

1. Prevent human consumption of shrimp from Shipyard Creek.

Robert L. Williams, Ph.D

Toxicologist

Concurrence: Lynn Wilder, CIH

Environmental Health Specialist

REFERENCE

1. Memorandum from U.S. Department of Commerce National Oceanic

and Atmospheric Administration, to Dr. Fred Holland, (Director) Marine Resources Research Institute,

Charleston, South Carolina, April 20, 1998.