V. Evaluation of Fish and Shellfish From Vieques

A. Introduction

What is meant by exposure?

ATSDR's PHAs are driven by exposure or contact. Chemicals released into the environment have the potential to cause harmful health effects. Nevertheless, a release does not always result in exposure. People can only be exposed to a chemical if they come in contact with that chemical. If no one comes into contact with a chemical, then no exposure occurs, thus no health effects could occur. Often the general public does not have access to the area where the environmental release occurs; however, it is important to determine whether the chemicals are moving through the environment to locations where people could come into contact with them.

The means in which a chemical moves through the environment, and how people contact the chemical, defines an exposure pathway. ATSDR identifies and evaluates exposure pathways by considering how people might come into contact with a chemical. In this public health assessment, ATSDR is evaluating exposures from eating potentially contaminated fish and shellfish from the coastal waters and near shore land on Vieques.

If someone is exposed, will they get sick?

Exposure does not always result in harmful health effects. The type and severity of health effects that occur in an individual as the result of contact with a chemical depend on the exposure concentration (how much), the frequency and duration of exposure (how long), and the multiplicity of exposure (combination of chemicals). Once exposure occurs, characteristics such as age, sex, nutritional status, genetics, lifestyle, and health status of the exposed individual influence how that individual absorbs, distributes, metabolizes, and excretes the chemical. Taken together, these factors and characteristics determine the health effects that can occur as a result of exposure to a chemical in the environment.

Considerable uncertainty exists regarding the true level of exposure to environmental contamination. To account for that uncertainty and to protect public health, ATSDR scientists typically use high-end, worst-case exposure level estimates to determine whether harmful health effects are possible. ATSDR used the following conservative approaches throughout this public health evaluation:

• ATSDR evaluated human exposure from consuming fish and shellfish from Vieques on a daily basis (i.e., 365 days per year) although an earlier survey by Universidad Metropolitana showed that only 16% of residents of Vieques eat fish five or more times a week (Caro et al. 2000).
  
• ATSDR calculated averages using detected concentrations only and did not take into account nondetected values. This tends to overestimate the true average values.
  
• In estimating the amount of inorganic arsenic, the most harmful form, from total arsenic in fish and shellfish, ATSDR assumed that 20% of the total arsenic detected was the inorganic form, even though FDA recommends that 10% of total arsenic be considered inorganic and as little at 1% may be inorganic (ATSDR 2000a; Francesconi and Edmonds 1997; NAS 2001b; FDA 1993).
  

Therefore, the estimated exposure levels are much higher than the levels to which people are really exposed. If the exposure levels indicate harmful health effects are possible, a more detailed review of exposure, combined with scientific information from the toxicologic and epidemiologic literature about the health effects from exposure to hazardous substances, is performed.

What exposure situations were evaluated in this PHA?

ATSDR focused this health evaluation on the edible samples that ATSDR worked with EPA/ERT to collect in July 2001 from six locations on and around Vieques, including five families of commonly caught and consumed fish and three species of shellfish (see Table 7). Fiddler crabs were not included in the health evaluation because it is ATSDR's understanding that fiddler crabs are not a species that people eat. Each of the other species was considered to equally represent fish or shellfish that are directly consumed by the residents of Vieques.

ATSDR evaluated several different consumption scenarios depending on a person's fish and shellfish intake. According to the survey conducted by Universidad Metropolitana, almost half the residents of Vieques eat fish one or two times a week. However, about 16% responded that they eat fish five or more times a week (Caro et al. 2000). Therefore, to account for the variability in dietary habits, ATSDR estimated exposure from eating fish or shellfish 7 days a week, 5 days a week, 4 days a week, 2 days a week, and 1 day a week. The scenario of eating fish or shellfish 7 days a week was evaluated first. If this intake level revealed a potential health hazard, ATSDR determined what a safe consumption level would be.

Individual metals in individual species varied from location to location (ATSDR 2002). Thus, it is possible that if someone were to regularly eat fish or shellfish caught from a single location rather than from a variety of locations, his/her metal intake level could be different than the average (either higher or lower than the average). Therefore, in addition to determining an overall exposure for people who eat fish and shellfish from a variety of locations surrounding Vieques, ATSDR also examined whether eating fish or shellfish from any specific location would cause people to experience adverse health effects.

Universidad Metropolitana questioned the residents of Vieques about the types of fish they eat and reported that yellowtail snapper was the most commonly consumed species of fish (Caro et al. 2000). Through talking with several Vieques fishermen and residents, including the petitioner, ATSDR confirmed that snapper were most commonly sought after, caught, and consumed than any other species of fish. Therefore, ATSDR also considered a specific situation where people ate snapper on a daily basis.

For reference, Appendix A is a glossary of environmental and health terms and Appendix D describes in greater detail the methods and assumptions ATSDR used to estimate human exposure doses and determine health effects.

B. Public Health Evaluation

Is it safe to eat fish and shellfish from Vieques?

Yes, the fish and shellfish from Vieques are safe to eat. Even though several metals were detected in some of the fish and shellfish, the concentrations that were present were too low to be of health concern in virtually all exposure situations evaluated. Appendix D describes in greater detail how ATSDR reached this conclusion.

Is it safe to eat fish and shellfish every day?

Yes, it is safe to eat a variety of fish and shellfish from Vieques on a daily basis. ATSDR evaluated this specific scenario in detail in Appendix D and determined that eating a variety of fish and shellfish would not result in adverse health effects or an increase in the risk of developing cancer.

Arsenic levels in lobsters

ATSDR evaluated arsenic concentrations in lobsters in detail in Appendix D because of their tendency to store arsenic that is naturally present in the environment (research has shown that marine organisms tend to accumulate arsenic naturally present in seawater and food, rather than only accumulating arsenic due to local pollution; Eisler 1994 as cited in ATSDR 2000a). The lobsters from Vieques did not contain higher levels of arsenic than FDA's level of concern for average consumption (76 ppm; FDA 1993). However, based upon a hypothetical exposure situation (eating lobsters from Vieques every day), using highly conservative assumptions (ATSDR assumed that 20% of the total arsenic is in the inorganic form), ATSDR found that eating more than two meals of lobster each week for 70 years could theoretically lead to harmful health effects. However, this finding is debatable because (1) there is much uncertainty surrounding the level at which health effects are seen and (2) according to the scientific research, the amount of arsenic present in lobsters from Vieques is low enough to be controlled by normal metabolic processes in the body (ATSDR 2000a). Please see the arsenic discussion in Appendix D for more details.

ATSDR concludes that lobsters from Vieques are safe to eat and only under highly unlikely, hypothetical scenarios with several levels of conservatism built into the evaluation might the arsenic levels in lobsters be a problem for people eating more than two meals of lobster a week for a lifetime.

Is it safe to eat fish and shellfish from any location?

Yes, it is safe to eat fish and shellfish from all of the areas that ATSDR sampled. Despite the fact that some metals were detected in higher concentrations at different locations, none were so much higher that ATSDR would expect to see adverse health effects in people who may solely eat fish or shellfish from a single location (e.g., only from the fish market or only from areas around the LIA). In other words, even though there are differences in fish and shellfish body burdens between locations, these differences are too small to have an impact on public health.

Is it safe to eat the most commonly caught and consumed fish every day?

ATSDR determined that it is safe to eat snapper, reportedly the most desirable and most commonly consumed species, on a daily basis. In Appendix D, under the section titled Special Case: Snapper, ATSDR describes in greater detail how this conclusion was reached.