Documents toxicology 183 results

"Objectives The purpose of this study was to evaluate empirically the relevance of animal-bioassay-based models for predicting human risks from exposure to 1,3-butadiene (BD) using epidemiologic data.Methods Relative-risk results obtained with a regression model in a recent epidemiologic study were used to estimate leukemia risk for occupational and environmental exposures to BD and to compare these estimates with those previously derived from an analysis of animal bioassay data.Results The estimates of risk were found to be highly dependent on the model used when low levels of exposure were evaluated that are of environmental concern, but not at the levels of occupational concern. For example, at the level (1 part per million) of the recently revised standard of the Occupational Safety and Health Administration in the United States the estimates of lifetime excess risk ranged from 1 to 8 per 1000 workers. The range of the risk estimates derived from the epidemiologic models was remarkably similar to the range of risk estimates for occupational exposures (1 to 9 per thousand) previously developed by Dankovic et al in 1993 from an analysis of a mouse bioassay study for lymphocytic lymphoma.Conclusions Results for BD seem to provide another example of a high degree of concordance between the risk predictions from models of toxicologic and epidemiologic data, particularly at occupational levels of exposure."

Beryllium is a steel-grey, brittle metal, existing naturally only as the 9Be isotope. Its compounds are divalent. Beryllium has several unique properties. It is the lightest of all solid and chemically-stable substances, with an unusually high melting point, specific heat, heat of fusion, and strength-to-weight ratio. It has excellent electrical and thermal conductivities. Because of its low atomic number, beryllium is very permeable to X-rays. Its nuclear properties include the breaking, scattering, and reflecting of neutrons, as well as the emission of neutrons on alpha-bombardment.

"This report provides a review of the cadmium exposure situation in Sweden and updates the information on health risk assessment according to recent studies on the health effects of cadmium. The report focuses on the health effects of low cadmium doses and the identification of high-risk groups.
The diet is the main source of cadmium exposure in the Swedish nonsmoking general population. The average daily dietary intake is about 15 µg /day, but there are great individual variations due to differences in energy intake and dietary habits. It has been shown that a high fiber diet and a diet rich in shellfish increase the dietary cadmium intake substantially. Cadmium concentrations in agricultural soil and wheat have increased continuously during the last century. At present, soil cadmium concentrations increase by about 0.2% per year. Cadmium accumulates in the kidneys. Human kidney concentrations of cadmium have increased several fold during the last century. Cadmium in pig kidney has been shown to have increased by about 2% per year from 1984–1992. There is no tendency towards decreasing cadmium exposure among the general nonsmoking population.
The absorption of cadmium in the lungs is 10–50%, while the absorption in the gastrointestinal tract is only a few percent. Smokers have about 4–5 times higher blood cadmium concentrations (about 1.5 µg/l), and twice as high kidney cortex cadmium concentrations (about 20–30 µg/g wet weight) as nonsmokers. Similarly, the blood cadmium concentrations are substantially elevated in persons with low body iron stores, indicating increased gastrointestinal absorption. About 10–40% of Swedish women of child-bearing age are reported to have empty iron stores (S-ferritin"

"Evaluates the risks to human health and the environment posed by 1,3-dichloropropene, 1,2-dichloropropane and mixtures of these chemicals. Since the two compounds and mixtures have been widely used in agriculture as pre-plant fumigants applied by soil injection, the report gives particular attention to studies investigating behaviour in soil, risks of leaching and groundwater contamination, uptake by food crops, residues detected in drinking-water and food, and risks to agricultural workers and the general population. Over 300 studies, including proprietary toxicological data from the manufacturers, were critically assessed.
The report concludes that, when used at the recommended rate, 1,3-dichloropropene is unlikely to attain levels of environmental significance. Risks to the general population were judged negligible. Concerning occupational hazards, the report cites evidence, largely from case reports of poisoning, underscoring the need to follow appropriate safety precautions.
The report concludes that 1,2-dichloropropane poses a negligible risk to the general population. When used at the recommended rate, the compound is unlikely to attain levels of environmental significance. For workers, the compound is judged unlikely to pose a hazard, provided good work practices, hygienic measures, and safety precautions are followed.
Data on mixtures of dichloropropenes and dichloropropane are evaluated in the final monograph. This technical mixture previously enjoyed wide use as a soil nematocide before planting. Citing evidence of a significant potential for 1,2-dichloropropane derived from this mixture to leach from soil and contaminate well water and groundwater, the report recommends that mixtures of dichloropropenes and dichloropropane should not be used as a soil fumigant. "

"Evaluates the risks to human health and the environment posed by benomyl, a fungicide registered for use in 50 countries on over 70 crops, including cereals, cotton, soybeans, tobacco, mushrooms, grapes, bananas and other fruits. One of the most widely used members of the benzimidazole family of fungicides, benomyl is effective, at low usage rates, against more than 190 different fungal diseases. Because benomyl is rapidly converted to carbendazim in the environment and is extensively metabolized to carbendazim by experimental animals, data from studies of carbendazim, which is a fungicide in its own right, are also considered when evaluating the hazards of benomyl.
Concerning hazards to environmental organisms, the report cites data from laboratory and field studies indicating that benomyl, applied at recommended rates, has little effect on soil microbial activity, but some adverse effects on groups of fungi. Benomyl is toxic to earthworms in laboratory experiments at realistic exposure concentrations and as a result of recommended usage in the field; earthworm populations may take more than two years to recover. Although high toxicity to aquatic organisms has been demonstrated in laboratory tests, the report concludes that this effect is unlikely to be seen in the field, due to the low bioavailability of sediment-bound residues.
For the general population, the main source of potential exposure is noted to be through the ingestion of food crops containing residues of benomyl and carbendazim. Though benomyl has been shown to cause contact dermatitis and dermal sensitization in some farm workers, the report found no evidence that either of these compounds can cause systemic toxic effects in occupationally exposed subjects or the general population. The report cites findings from animal studies suggesting that both compounds pose a very low risk for acute poisoning in humans."

Evaluates the risks to human health and the environment posed by methyl parathion, a highly toxic organophosphorus ester insecticide. Close to 600 studies were critically assessed. Introduced as a commercial chemical in 1949, methyl parathion is used as a contact insecticide and acaricide for the protection of cotton, soybeans, cereals, tobacco, peanuts, vegetables, citrus fruits, and other crops. The compound is applied as a foliar spray by aircraft or ground equipment.

Because methyl parathion is a non-selective pesticide that kills beneficial species as well as pests, a section devoted to effects on environmental organisms concentrates on several studies documenting high toxicity for honey bees. These studies also show that incidents of bee kills were more severe with this insecticide than with others, underscoring the need to time spraying operations with extreme care. The report concludes that methyl parathion should never be sprayed under windy conditions, and that overspraying of water bodies must be avoided.

The most extensive section evaluates studies of toxic effects observed in experimental animals and in vitro test systems. The report found no evidence of carcinogenicity associated with long-term exposure, and no evidence that this insecticide acts as a primary eye or skin irritant. The final section evaluates effects on humans, drawing on a number of case reports of accidental and sometimes fatal poisoning. The report concludes that the only confirmed effects on humans are the signs and symptoms characteristic of systemic poisoning by cholinesterase-inhibiting organophosphorus compounds. No cases of organophosphorus-induced, delayed peripheral neuropathy have been reported. Concerning risks to workers, the report concludes that, with good work practices, hygienic measures, and safety precautions, methyl parathion is unlikely to present a hazard for occupationally exposed workers.