Human health hazards associated with chemical contamination of aquatic environment.

Given the finite supply of water available for human use, continued chemical contamination of the aquatic environment may pose a significant human health hazard. Consequently, an effort must be made to develop ambient water quality criteria to protect human health and preserve the integrity of the aquatic environment. In developing water quality criteria based on human health effects, information on sources of exposure, pharmacokinetics, and adverse effects must be carefully evaluated. Information on sources of exposure is needed to determine the contribution of exposure from water relative to all other sources. Pharmacokinetic data are used in inter- and intraspecies extrapolation and in characterizing the mode of toxic action. Information on toxic effects includes data on acute, subchronic, and chronic toxicity, mutagenicity, teratogenicity, and carcinogenicity. In analyzing such information, a distinction is made between threshold and nonthreshold effects. Currently, carcinogenicity and mutagenicity are considered to be nonthreshold effects. For carcinogens and mutagens, criteria are calculated by postulating an "acceptable" increased level of risk and using extrapolation models to estimate the dose which would result in this increased level of risk. For other chemicals, thresholds are assumed and criteria are calculated by deriving "acceptable daily intakes" for man which would presumably result in no observable adverse effects. Neither process is exact, and attempts must be made to improve and verify risk assessment methodologies.

The toxicologic effects of the carbamate insecticide aldicarb in mammals: a review.

Aldicarb, 2-methyl-2-(methylthio)propionaldehyde-O-methylcarbamoyloxime, is an oxime carbamate insecticide manufactured by the Union Carbide Corporation and sold under the trade name Temik. It is a soil-applied systemic pesticide used against certain insects, mites, and nematodes, and is applied below the soil surface for absorption by plant roots. It is generally applied to the soil in the form of 5, 10, or 15% granules, and soil moisture is essential for the release of the toxicant. Uptake by plants is rapid. Aldicarb is currently registered for use on cotton, sugar beets, sugar cane (Louisiana only), potatoes, sweet potatoes, peanuts, oranges, pecans (Southeast only), dry beans, soybeans, and ornamental plants. Home and garden use is not permitted. Discovery of aldicarb and its oxidative sulfoxide and sulfone metabolites in well or ground water in Florida, Wisconsin, and New York, and accidental poisonings from ingesting contaminated watermelons and cucumbers in the South and West have spurred interest and concern about this pesticide. The primary mechanism of toxic action of aldicarb is cholinesterase inhibition. However, unlike the relatively irreversible anticholinesterase activity of the organophosphate pesticides, the carbamylation process which produces the anti-AChE action is quickly reversible. Aldicarb is readily absorbed through both the gut and the skin, but is rapidly metabolized and excreted in the urine almost completely within 24 hr. Although it is acutely toxic to humans and laboratory animals, aldicarb is not known to be carcinogenic, teratogenic, conclusively mutagenic, or to produce other long-term adverse health effects. In cases of accidental poisoning, the cholinergic symptoms have generally subsided within 6 hr, with no side effects or complications.

The current use of studies on promoters and cocarcinogens in quantitative risk assessment.

Several of the priority pollutants discussed in EPA's Ambient Water Quality Criteria documents have been reported to have promotion or cocarcinogenic activity. For example, phenol appears to have tumor-promoting activity in mice when repeatedly applied after initiation with either 7,12-dimethyl-1,2-benzanthracene (DMBA) or benzo(a)pyrene (BaP). Similarly, it has been reported that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent promoter of liver tumors as well as a cocarcinogen. However, in developing guidelines to derive ambient water quality criteria, it became apparent that satisfactory approaches had not been developed for using promotion/cocarcinogen data in human health risk estimation, nor were available promotion and/or cocarcinogen data on individual chemicals strong enough to permit a defensible quantitative risk estimation, if such approaches had existed. For this reason, the criteria derived for pollutants with reported promotion/cocarcinogenic activities were based on approaches for carcinogenic (e.g., TCDD), toxic (e.g., fluoranthene) or organoleptic effects (e.g., 2,4-dichlorophenol). Nonetheless, with advances in studies on both the biological mechanisms and dose/response patterns of promoters and cocarcinogens, it may be possible to develop a scientifically valid quantitative approach to use this type of data for derivation of ambient water quality criteria or other risk assessments. Some progress toward this goal and the problems associated with this effort are discussed.

Inhalation toxicology of automotive emissions as affected by an oxidation exhaust catalyst.

Preliminary data are given on the acute inhalation toxicology of automotive emissions as affected by an oxidation exhaust catalyst. The catalyst effectively reduced CO and HC in the exhause which apparently had an effect (at least in a closed exposure system) on oxidant and NO2 levels by altering the HC/NOx ratio. There was a resultant reduction in biological effects due to the exposure. The catalyst altered the type of particulate to one which probably contained sulfuric acid as a major component. No evidence was present in these acute exposures to suggest a toxic response due to the higher sulfate emissions or possible catalyst attrition products. The effects of long-term exposure have not yet been investigated.

Whole body retention in rats of different 191Pt compounds following inhalation exposure.

The whole body retention, excretion, lung clearance, distribution, and concentration of 191Pt in other tissues was determined in rats following a single inhalation exposure to different chemical forms of 191Pt. The chemical forms of 191Pt used in study were 191PtCl4, 191Pt(SO4)2, 191PtO, and 191Pt metal. Immediately after exposure most of the 191Pt was found in the gastrointestinal and respiratory tract. Movement of the 191Pt through the gastrointestinal tract was rapid, most of the 191Pt being eliminated within 24 hr after exposure. Lung clearance was much slower, with a clearance half-time of about 8 days. In addition to the lungs, kidney and bone contained the highest concentrations of 191Pt.

The environmental dynamics of the carbamate insecticide aldicarb in soil and water.

Aldicarb is a soil-applied systemic pesticide the USEPA is now considering banning in the USA. Aldicarb is fairly rapidly oxidized to the sulfoxide, with a half-life of approximately 7 days in some soils, and much more slowly to the sulfone (pH-dependent with half-lives varying from a few minutes at a pH of > 12 to approximately 560 days at a pH of 6.0). Persistence, carry-over and translocation vary with soil and environmental conditions. Drainage aquifers and drinking water wells are known to be susceptible to contamination, levels of approximately 550 ppb have been recorded. Foods are also known to take up the pesticide; levels of 600 ppb have been found in potatoes.

Chronic and reproduction studies in rats exposed to gasifier ash leachates.

Ash from the coal gasification process contains a broad spectrum of elements which through leaching (gasifier ash leachates) may enter into the environment. The health effect of such leachates i.e. complex mixtures of inorganic elements is insufficiently known. We investigated the effect of gasifier ash leachates in a chronic-(9-month) and in a three-generation reproduction study. The leachates were prepared weekly by water extraction of ash from a Lurgi coal gasification plant in Yugoslavia, and given to experimental animals instead of drinking water. In the chronic experiment exposed animals showed no changes in mortality rate, haematological findings, concentration of Fe, Zn, Mn in kidneys, liver, testicles and femur, as well as in femur composition and morphometry, gross pathology and organ histology. In the reproduction study the number of pregnancies, weight and number of newborns, and concentration of Fe, Zn, Mn in carcasses of sucklings were the same in control and experimental animals.

Dermal irritancy of metal compounds. Studies with palladium, platinum, lead, and manganese compounds.

Dermal irritancy of 14 materials, including several compounds of palladium, platinum and lead, and methylcyclopentadienyl manganese tricarbonyl, plus deionized water (negative control) and glacial acetic acid (positive control), was tested on male albino rabbits weighing 2 to 3 kg. Procedures and evaluation criteria were adopted from those in use by the National Institute for Occupational Safety and Health. Five materials were evaluated as unsafe for intact or abraded skin contact as judged by severity of responses: glacial acetic acid (C3H5PDCl)2, (NH4)2PdCl4, (NH4)2PdCl6, and PtCl4; one as safe for intact, but not for abraded, skin: K2PdCl6; and two as safe for intact skin but not for abraded skin unless protected: K2PdCl4 and PdCl2. The remainder were evaluated as safe for intact or abraded skin contact (irritancy grade less than 1 on a scale of 4): H2O, Pd(NH3)2Cl2, PdO, PtO2, PtCl2, PbCl2, PbO, MMT.

First generation of a new science: risk assessment in transition.

The greatest challenge facing human populations today is that of extraordinary rapid change. Such a change in the society is illustrated by the increasing public awareness of environmental issues, accompanied by continuously expanding scientific investigations of chemical pollution. Our industrial civilization has developed and introduced into the various environmental media many compounds affecting human health individually and as a society. The science of toxicology is the evaluation of the effects of chemical and physical agents in various biological systems. Most chemical compounds cannot be tested in man due to their possible carcinogenic, mutagenic, teratogenic, or other long-term toxic potential. Therefore, carefully designed toxicologic studies in other species, especially mammalian, are conducted to provide biological dose-response data, which can be used to predict human response. Toxicologists have the responsibility of providing accurate scientific dose-response data based on experiments employing, among others, "practical" concentrations of pollutants or toxicants. When the toxic effects are considered, the action of these agents in the atmosphere, water, and other environmental vehicles should be considered. There are always interacting events that co-exist in the environment. Multiple causality as a factor of a disease is well established but frequently overlooked. The various issues in environmental health need to be tied together in order to be understood by scientists who are not intimately familiar with risk assessment procedures as they relate to the implementation of environmental laws. Much effort is needed both in the area of improved risk assessment methodology as well as in the area of toxicologic testing and validation of the theoretical approaches.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulatory history and experimental support of uncertainty (safety) factors.

A synthesis of available literature on uncertainty (safety) factors which are used to estimate acceptable daily intakes (ADIs) for toxicants is presented. This synthesis reveals reasonable qualitative biological premises, as well as specific biological data that support both the use and choice of these factors. A suggestion is made in order to derive a range of ADI. Research needs in various areas of uncertainty are also identified.

Health and environmental effects profile for pentachloronitrobenzene.

Pure pentachloronitrobenzene (PCNB) is a colorless crystalline solid (Worthing, 1983). The commercial product may have a light-yellow to cream color with a musty odor (Hartley and Kidd, 1983). It is practically insoluble in a number of organic solvents. The compound is reasonably stable but may undergo hydrolysis in a strong alkaline medium (Hartley and Kidd, 1983). In 1983, Olin Corp., Leland, MS, was the only manufacturer of PCNB in the United States (SRI, 1984; Hartley and Kidd, 1983). No data for U.S. production volume for this chemical are available, but recent production source data (USITC, 1985; SRI, 1985) suggest that this chemical is no longer commercially produced in the United States. The primary usage of PCNB is as a soil fungicide for a wide variety of crops and in seed treatment (Worthing, 1983; Hartley and Kidd, 1983). The fate of PCNB in water has not been comprehensively studied. Only qualitative data regarding fate and transport in water are available. The half-life of PCNB in the water phase was estimated to be 1.8 days. The two processes reported to be most responsible for the rapid decrease in PCNB concentration in water were volatilization and sorption to seston and biota, followed by sedimentation as detritus (Schauerte et al., 1982). Neither biodegradation nor photolysis appears to be a significant process for the loss of PCNB from water (Crosby and Hamadmad, 1971; Schauerte et al., 1982). The BCFs for PCNB in the golden orfe, Leucisens idus melanotus, and in rainbow trout, Salmo gairdneri, were reported to be 950-1130 and 260-590, respectively (Korte et al., 1978; Oliver and Niimi, 1985). It therefore appears that PCNB will moderately bioaccumulate in aquatic organisms. Pertinent data regarding the fate and transport of PCNB in air could not be located in the available literature as cited in the Appendix. Based on its physical properties and its behavior in other media, it would appear that PCNB will persist in the atmosphere because no known chemical/photochemical processes significantly degrade this chemical. Precipitation of particulate PCNB, especially of larger particle size and higher particle density, may remove some PCNB from the atmosphere. PCNB is persistent in soils. The two processes that are important in the loss of PCNB from soils are volatilization and biodegradation; biodegradation is more rapid in soils under anaerobic conditions than under aerobic conditions (Ko and Farley, 1969; Casley, 1968; Gile and Gillett, 1979; Cole and Metcalf, 1977).(ABSTRACT TRUNCATED AT 400 WORDS)