Michael Gochfeld

Cases of mercury exposure, bioavailability, and absorption

Mercury is a unique element that, unlike many metals, has no essential biological function. It is liquid at room temperature and is 13.6 times heavier than water. Its unique physical properties have been exploited for a variety of uses such as in mercury switches, thermostats, thermometers, and other instruments. Its ability to amalgamate with gold and silver are used in mining these precious metals and as a dental restorative. Its toxic properties have been exploited for medications, preservatives, antiseptics, and pesticides. For these reasons there have been many industrial uses of mercury, and occupational exposures of workers and industrial emissions and effluents contaminating air, water, soil, and ultimately food chains have long been a matter of great public health concern. This paper examines briefly six cases representing various forms of exposure to different species of mercury, and indicates the methodological issues in estimating exposure, bioavailability and absorption; these cases include Minamata disease in Japan, organic mercury poisoning in Iraq, methylmercury (MeHg) exposure in the Amazon, dimethylmercury (PMM) in the laboratory, an elemental mercury spill in Cajamarca, Peru, and a mercury-contaminated building in Hoboken, NJ, USA. Other scenarios that are not described include occupational exposure to mercury salts, mercurial preservatives in vaccines, cultural and ritualistic uses of mercury, and mercury in dental amalgams.

Estimating Annual Survival and Movement Rates of Adults within a Metapopulation of Roseate Terns

Several multistratum capture-recapture models were used to test various hypotheses about possible geographic and temporal variation in survival, movement, and recapture/resighting probabilities of 2399 adult Roseate Terns (Sterna dougallii) color-banded from 1988 to 1992 at the sites of the four largest breeding colonies of this species in the northeastern USA. Linear-logistic ultrastructural models also were developed to investigate possible correlates of geographic variation in movement probabilities. Based on goodness-of-fit tests and comparisons of Akaikes Information Criterion (AIC) values, the fully parameterized model (Model A) with time- and location-specific survival, movement, and capture probabilities, was selected as the most appropriate model for this metapopulation structure. With almost all movement accounted for, on average >90% of the surviving adults from each colony site returned to the same site the following year. Variations in movement probabilities were more closely associated with the identity of the destination colony site than with either the identity of the colony site of origin or the distance between colony sites. The average annual survival estimates (0.74-0.84) of terns from all four sites indicate a high rate of annual mortality relative to that of other species of marine birds.

Lessons from case studies of metals: investigating exposure, bioavailability, and risk

Since metals are widely distributed in environmental matrices, humans are exposed to them by either anthropogenic activities or inadvertently by necessity. Selected metals: arsenic, mercury, iron, tin, lead and chromium were chosen on the basis of their economic and public health importance to illustrate the diversity of exposure pathways and differences in factors governing bioavailability. Bioavailability is central to the toxicity of metals and this is discussed from the health risk paradigm standpoint of risk assessment and risk management and the impacts of including or excluding bioavailability in such assessment. The lessons from the case studies of arsenic, mercury, tin and chromium provide a unified concept of methods that can be used in investigating and controlling outbreaks due to metal poisoning in other similar situations.

Metal levels in feathers of 12 species of seabirds from Midway Atoll in the northern Pacific Ocean

Seabirds are excellent subjects for examination of heavy metals because they are long-lived, feed at different distances from land, and exhibit different trophic levels. In this paper we compare the levels of lead, cadmium, mercury arsenic, chromium, manganese, selenium, and tin in the feathers of birds nesting on Midway Atoll in the northern Pacific Ocean. We test the null hypothesis that there are no interspecific differences in the levels of metals in the feathers of the adult black-footed albatross (Diomedea nigripes), Laysan albatross (Diomedea immutabilis), red-footed booby (Sula sula), great frigatebird (Fregata minor), Bonin petrel (Pterodroma hypoleuca), Christmas shearwater (Puffinus nativitatis), red-tailed tropicbird (Phaethon rubricauda), wedge-tailed shearwater (Puffinus pacificus), brown noddy (Anous stolidus), sooty tern (Stema fuscata), grey-backed tern (Stema lunata), and white tern (Gygis alba), and young of some of these species. There were interspecific differences in the levels of all metals for adults. Christmas shearwater had the highest levels of lead, cadmium, selenium and manganese, but the second lowest levels of mercury. In general, metal levels were the lowest in the smallest species (white tern), but were not the highest in the largest species (black-footed albatross), except for manganese, arsenic and mercury. There was a high variance in metal levels among adults for some species, but not for others. White tern adults were variable for lead, while Christmas shearwaters were variable for lead and cadmium. Compared to the means for metals in other birds generally (after Burger, 1993), Christmas shearwaters had higher levels of lead, white terns, brown noddy, Christmas shearwater, frigatebirds and Laysan albatrosses had higher levels of cadmium, and bonin petrel, wedge-tailed shearwater, tropicbirds, frigatebirds, red-footed boobies, and both albatrosses had higher levels of mercury. Whereas the means for lead and cadmium were below the known effects levels, some individuals had levels high enough to cause adverse effects in the birds. The mean values for mercury in Bonin petrel, red-tailed tropicbird, and black-footed albatross were higher than the levels known to cause adverse reproductive and behavioral effects.

EFFECTS OF LEAD ON BIRDS (LARIDAE): A REVIEW OF LABORATORY AND FIELD STUDIES

Lead is one of the most common metals in contaminated ecosystems. Although lead poisoning and mortality have long been known, little is known of the behavioral effects produced by low levels of lead in wild animals. Herein a 15-yr research program on the behavioral effects of lead using herring gulls (Larus argentatus) and common terns (Sterna hirundo), referred to as larids, as models is reviewed. The doses used in laboratory studies were sufficient to produce lead concentrations in feathers that were equivalent to those found in some birds living in the wild. The exposure consisted of a single or multiple intraperitoneal (ip) injection of lead acetate. Both dose and day of exposure influenced behavioral development in young larids, with most effects increasing with dose, and decreasing with age. Low-level lead affected growth, locomotion, balance, food begging, feeding, thermoregulation, depth perception, and individual recognition in laboratory and in wild birds. The accuracy of individual recognition was most affected by lead exposure from 2 to 6 d of age; exposure at 12 d did not affect accuracy, but it delayed response time significantly. Behavioral deficits observed in lead-injected young in the wild were similar to those observed in the laboratory, except that recovery was more complete by fledging than it was in laboratory-raised chicks. Further, parents in the wild were able to provision lead-exposed chicks sufficiently so that they fledged at similar weights as control chicks, a feat that is difficult to achieve in the laboratory. The lead-induced behavioral deficits observed in the laboratory and in the wild are sufficient to affect growth and survival in wild herring gulls. Lead treatment altered the expression of cell adhesion molecules (CAMs), which play a crucial role in the formation and deployment of neurons in the developing brain. The timing and sequencing of CAM expression is critical to normal development, and the different consequences of lead exposure at different ages may be related to interference at different points in the sequence.

Mercury in Commercial Fish: Optimizing Individual Choices to Reduce Risk

Most attention to the risks from fish consumption has focused on recreational anglers and on fish caught by individuals, but the majority of fish that people eat are purchased from commercial sources. We examined mercury levels in three types of fish (tuna, flounder, bluefish) commonly available in New Jersey stores, sampling different regions of the state, in communities with high and low per capita incomes, and in both supermarkets and specialty fish markets. We were interested in species-specific levels of mercury in New Jersey fish and whether these levels were similar to data generated nationally by the Food and Drug Administration (FDA; mainly from 1990 to 1992) on the same types of fish. Such information is critical for providing public health advice. We were also interested in whether mercury levels in three common species of fish differed by region of the state, economic neighborhood, or type of store. We found significant species differences, with tuna having the highest levels and flounder the lowest levels. There were no significant differences in mercury levels as a function of type of store or economic neighborhood. There was only one regional difference: flounder from fish markets along the Jersey shore had higher mercury levels than flounder bought in other markets. We also examined mercury levels in six other commonly available fish and two shellfish from central New Jersey markets. There were significant differences in availability and in mercury levels among fish and shellfish. Both shrimp and scallops had total mercury levels < 0.02 ppm (wet weight). Large shrimp had significantly lower levels of mercury than small shrimp. For tuna, sea bass, croaker, whiting, scallops, and shrimp, the levels of mercury were higher in New Jersey samples than those reported by the FDA. Consumers selecting fish for ease of availability (present in > 50% of markets) would select flounder, snapper, bluefish, and tuna (tuna had the highest mercury value), and those selecting only for price would select whiting, porgy, croaker, and bluefish (all with average mercury levels < 0.3 ppm wet weight). Flounder was the fish with the best relationship among availability, cost, and low mercury levels. We suggest that state agencies responsible for protecting the health of their citizens should obtain information on fish availability in markets and fish preferences of diverse groups of citizens and use this information to select fish for analysis of contaminant levels, providing data on the most commonly eaten fish that will help people make informed decisions about risks from fish consumption.

Human Activity Influence and Diurnal and Nocturnal Foraging of Sanderlings (Calidris alba)

We studied the foraging behavior of Sanderlings (Calidris alba) in the winter of 1986, 1988 and 1990 in Florida to determine whether the presence of people influenced foraging behavior, and whether foraging behavior varied as a function of time of day. We used a focal animal sampling approach. For all three years, the models explaining the greatest variation in seconds per minute devoted to feeding included the number of people within 100 m of foraging Sanderlings. Although the number of people within 10 m of foraging Sanderlings during the day did not increase from 1986 to 1990, the number of people within 100 m rose dramatically, and foraging time per minute decreased. Sanderlings continued to feed through dusk into night and the time devoted to foraging and to aggression was greater at night, while the time devoted to avoiding people was less at night than during daylight or dusk.

Mercury and selenium levels in 19 species of saltwater fish from New Jersey as a function of species, size, and season

There are few data on risks to biota and humans from mercury levels in saltwater fish. This paper examines mercury and selenium levels in muscle of 19 species of fish caught by recreational fisherfolk off the New Jersey shore, as a function of species of fish, size, and season, and risk of mercury to consumers. Average mercury levels ranged from 0.01 ppm (wet weight) (Menhaden Brevoortia tyrannus) to 1.83 ppm (Mako Shark Isurus oxyrinchus). There were four categories of mercury levels: very high (only Mako), high (averaging 0.3-0.5 ppm, 3 species), medium (0.14-0.20 ppm, 10 species), and low (below 0.13 ppm, 5 species). Average selenium levels for the fish species ranged from 0.18 ppm to 0.58 ppm, and had lower variability than mercury (coefficient of variation=38.3 vs 69.1%), consistent with homeostatic regulation of this essential element. The correlation between mercury and selenium was significantly positive for five and negative for two species. Mercury levels showed significant positive correlations with fish size for ten species. Size was the best predictor of mercury levels. Selenium showed no consistent relationship to fish length. Over half of the fish species had some individual fish with mercury levels over 0.3 ppm, and a third had fish with levels over 0.5 ppm, levels that pose a human health risk for high end consumers. Conversely several fish species had no individuals above 0.5 ppm, and few above 0.3 ppm, suggesting that people who eat fish frequently, can reduce their risk from mercury by selecting which species (and which size) to consume. Overall, with the exception of shark, Bluefin Tuna (Thunnus thynnus), Bluefish (Pomatomus saltatrix) and Striped Bass (Morone saxatilis), the species sampled are generally medium to low in mercury concentration. Selenium:mercury molar ratios were generally above 1:1, except for the Mako shark.

Ethnic differences in risk from mercury among Savannah River fishermen.

Fishing plays an important role in peoples lives and contaminant levels in fish are a public health concern. Many states have issued consumption advisories; South Carolina and Georgia have issued them for the Savannah River based on mercury and radionuclide levels. This study examined ethnic differences in risk from mercury exposure among people consuming fish from the Savannah River, based on site-specific consumption patterns and analysis of mercury in fish. Among fish, there were significant interspecies differences in mercury levels, and there were ethnic differences in consumption patterns. Two methods of examining risk are presented: (1) Hazard Index (HI), and (2) estimates of how much and how often people of different body mass can consume different species of fish. Blacks consumed more fish and had higher HIs than Whites. Even at the median consumption, the HI for Blacks exceeded 1.0 for bass and bowfin, and, at the 75th percentile of consumption, the HI exceeded 1.0 for almost all species. At the White male median consumption, noHI exceeded 1, but for the 95th percentile consumer, the HI exceeded 1.0 almost regardless of which species were eaten. Although females consumed about two thirds the quantity of males, HIs exceeded 1 for most Black females and for White females at or above the 75th percentile of consumption. Thus, close to half of the Black fishermen were eating enough Savannah River fish to exceed HI = 1. Caution must be used in evaluating an HI because the RfDs were developed to protect the most vulnerable individuals. The percentage of each fish species tested that exceeded the maximum permitted limits of mercury in fish was also examined. Over 80% of bowfin, 38% of bass, and 21% of pickerel sampled exceeded 0.5 ppm. The risk methodology is applicable anywhere that comparable data can be obtained. The risk estimates are representative for fishermen along the Savannah River, and are not necessarily for the general populations.

Factors in Exposure Assessment: Ethnic and Socioeconomic Differences in Fishing and Consumption of Fish Caught along the Savannah River

South Carolina has issued fish consumption advisories for the Savannah River based on mercury and radionuclide levels. We examine differences in fishing rates and fish consumption of 258 people interviewed while fishing along the Savannah River, as a function of age, education, ethnicity, employment history, and income, and test the assumption that the average consumption of fish is less than the recreational value of 19 kg/year assumed by risk assessors. Ethnicity and education contributed significantly to explaining variations in number of fish meals per month, serving size, and total quantity of fish consumed per year. Blacks fished more often, ate more fish meals of slightly larger serving sizes, and consumed more fish per year than did Whites. Although education and income were correlated, education contributed most significantly to behavior; people who did not graduate from high school ate fish more often, ate more fish per year, and ate more whole fish than people who graduated from high school. Computing consumption of fish for each person individually indicates that (1) people who eat fish more often also eat larger portions, (2) a substantial number of people consume more than the amount of fish used to compute risk to recreational fishermen, (3) some people consume more than the subsistence level default assumption (50 kg/year) and (4) Blacks consume more fish per year than Whites, putting them at greater risk from contaminants in fish. Overall, ethnicity, age, and education contributed to variations in fishing behavior and consumption.