Inorganic arsenic: a need and an opportunity to improve risk assessment.

This paper presents views on the current status of (inorganic) arsenic risk assessment in the United States and recommends research needed to set standards for drinking water. The opinions are those of the Arsenic Task Force of the Society for Environmental Geochemistry and Health, which has met periodically since 1991 to study issues related to arsenic risk assessment and has held workshops and international conferences on arsenic. The topic of this paper is made timely by current scientific interest in exposure to and adverse health effects of arsenic in the United States and passage of the Safe Drinking Water Act Amendment of 1996, which has provisions for a research program on arsenic and a schedule mandating the EPA to revise the maximum contaminant level of arsenic in drinking water by the year 2001. Our central premise and recommendations are straightforward: the risk of adverse health effects associated with arsenic in drinking water is unknown for low arsenic concentrations found in the United States, such as at the current interim maximum contaminant level of 50 microg/l and below. Arsenic-related research should be directed at answering that question. New epidemiological studies are needed to provide data for reliable dose-response assessments of arsenic and for skin cancer, bladder cancer, or other endpoints to be used by the EPA for regulation. Further toxicological research, along with the observational data from epidemiology, is needed to determine if the dose-response relationship at low levels is more consistent with the current assumption of low-dose linearity or the existence of a practical threshold. Other recommendations include adding foodborne arsenic to the calculation of total arsenic intake, calculation of total arsenic intake, and encouraging cooperative research within the United States and between the United States and affected countries.

Two-stage evaluation of exposure to mercury and biomarkers of neurotoxicity at a hazardous waste site.

Communities surrounding the Rocky Mountain Arsenal (RMA), a Superfund site in Colorado, were studied in order to determine whether exposures to mercury were greater among persons who resided there than among residents of a comparison area 12-15 miles distant. From a census-based stratified random sample, 469 persons were interviewed and urine samples were obtained for biomonitoring. Mercury was detected in urine from 32 (6.8%) of the 469 persons sample at a detection limit of 5 ppb. Trace levels of mercury (detectable, but nonquantifiable) were found in 80 (17.1%) of the persons sampled. Neither the frequency of detection, the arithmetic mean, nor the geometric mean value for urine mercury was found to be statistically different when persons living near the site were compared to persons from the more distant comparison area. The risk of mercury exposure associated with demographic variables, residence, occupation, hobbies, dietary habits, water supply, housing, and activity patterns was evaluated. In the second stage of the evaluation, the Neurobehavioral Core Test Battery (NCTB) is being used to assess individual functional deficits and nervous system disorders associated with exposure to mercury and other neurotoxic chemicals.

Risk factors for exposure to arsenic at a hazardous waste site.

Communities surrounding the Rocky Mountain Arsenal (RMA), a Superfund site in Colorado, were studied in order to determine whether exposures to arsenic were greater among persons who resided there than among residents of a comparison area. A census was conducted in areas adjacent to the RMA and in a comparison area 12-15 miles distant. From a stratified random sample, 469 persons were interviewed and urine samples obtained. Arsenic was detected in urine from 43 (9.2%) of the 469 persons sampled at a detection limit of 10 ppb. Trace levels of arsenic (detectable, but non-quantifiable) were found in 184 (39.2%) of those persons sampled. Neither the frequency of detection, the arithmetic mean nor the geometric mean values for urine arsenic was found to be statistically different when persons living near the site were compared to persons from the more distant comparison area. Therefore, the data were pooled across the study areas to evaluate risk factors for exposure to arsenic in this population-based sample. Multivariate logistic regression analyses were conducted to evaluate the risk of arsenic exposure associated with variables included in the interviews while controlling for confounding. Pathways for exposure to arsenic were evaluated through analysis of residence history, occupation, hobbies, dietary habits, water supply, housing and activity patterns. Children of Hispanic origin or non-white race, children who drank less than three glasses of water daily, and children who spent more time outdoors had an increased risk of having > or = 10 ppb of arsenic in their urine. Among adults, younger persons, especially those less than 40 years of age, persons of Hispanic origin or nonwhite race, and those employed in occupations where arsenic is likely to be found had an increased risk of having > or = 10 ppb of urine arsenic. Consumption of red wine or fish during the week prior to sampling was associated with trace levels of arsenic in urine.

Occupational reproductive hazards: necessary steps to prevention.

Although some attention has recently been given to the study of occupational reproductive hazards, little is known about measures being taken to prevent exposure to substances having the potential to cause such problems. In the past, OSHA has promulgated a standard to lower the permissible exposure level to a reproductive toxin as the major focus only after experimental evidence was confirmed in humans. The method of selection of appropriate substitutes is also cause for concern. A chemical known to cause testicular atrophy, cancer, and gene mutations in subhuman test systems and to cause sterility in male workers was replaced with a substance known from experimental studies to cause testicular toxicity, cancer of multiple sites, and gene mutations. Experimental test results need to be addressed from the standpoint of determining presumptive risk to humans. A scheme for setting priorities for reduction of exposure or for consideration of regulation of occupational reproductive hazards also needs to be developed. A policy addressing occupational reproductive hazards may serve as a stimulus for protecting workers from these hazards and for improving scientific research protocols.

Molybdenum in the diet: an estimate of average daily intake in the United States.

Previous studies have estimated the average intake of molybdenum (Mo) from the diet at approximately 300 to 400 micrograms/day. Foods collected in a grocery basket sampling program were analyzed for Mo content. The Mo concentration of these foods was combined with published United States Department of Agriculture estimates of food consumption to estimate the average daily dietary intake of Mo in the United States. This estimate is less than those previously reported and varies between 120 and 240 micrograms Mo/day, depending on age, sex, and income.

Cadmium exposure in a community near a smelter.

In June, 1976, the authors conducted a cross-sectional survey of a community near a cadmium smelter in Denver, Colorado, to evaluate human cadmium absorption and its possible health effects. In 1975 the mean annual airborne cadmium concentration in an area about 1 km from the smelter was 0.023 microgram/m3; the mean concentration in a comparison area 13 km distant was 0.003 microgram/m3. Whole blood and urine specimens were collected from 250 individuals residing within 2 km of the smelter and from a control population of 105 residents in the comparison area. There were no significant differences (p greater than .05) in whole blood or urine cadmium concentrations, as determined by flameless atomic absorption spectrophotometry, between persons in the two areas. The median blood and urine cadmium concentrations of residents within 1 km of the smelter were 0.05 and 0.09 microgram/100 ml, compared with 0.07 and 0.08 microgram/100 ml for control area residents. However, the difference between blood cadmium levels for smokers and nonsmokers was statistically significant (p less than .01). The median blood cadmium concentration for smokers was 0.21 microgram/100 ml compared with 0.04 microgram/100 ml for nonsmokers. Other laboratory determinations of blood and urine showed no evidence of a cadmium effect on hematopoietic or renal function.