Chemicals long term effects

Workers in the metals treatment industry are exposed to fumes, dusts, and mists containing metals and metal compounds, as well as to various chemicals from sources such as grinding wheels and lubricants. Exposure can be by inhalation, ingestion, or skin contact. Historically, metal toxicology was concerned with overt effects such as abdominal coHc from lead toxicity. Because of the occupational health and safety standards of the 1990s such effects are rare. Subtie, chronic, or long-term effects of metals treatment exposure are under study. An index to safety precautions for various metal treatment processes is available (6). As additional information is gained, standards are adjusted. 

CFCs represent only one class of chemicals being released to the atmosphere which have long-term effects. Replacement chemicals will be re-... 

After the use of a chemical becomes widespread, new deleterious effects on human health may be observed. In such situations, the occupational limit values will have to be modified. Usually the OELS tend to decrease when more information on the toxicity of a chemical is obtained. Knowledge of the specific features of various chemicals is thus extremely important for planning ventilation of industrial premises. It is important to be especially aware of those chemicals that may cause long-term effects without causing any acute effects. There are also compounds such as isocyanates that are extremely irritating at concentrations as low as 0.5 ppm. However, some workers may become sensitized to isothiocyanates at a concentration of 10 ppb, and therefore this has to be taken into consideration when planning the industrial ventilation. Thus, one has to plan against compounds that can cause serious health effects at concentrations at which their presence cannot be observed by the human senses, i.e., irritation or odor. 

Most of the materials used in the manufacture of chemicals are poisonous, to some extent. The potential hazard will depend on the inherent toxicity of the material and the frequency and duration of any exposure. It is usual to distinguish between the short-term effects (acute) and the long-term effects (chronic). A highly toxic material that causes immediate injury, such as phosgene or chlorine, would be classified as a safety hazard. Whereas a material whose effect was only apparent after long exposure at low concentrations, for instance, carcinogenic materials, such as vinyl chloride, would be classified as industrial... 

Lay, J.P., A. Muller, L. Peichl, W. Klein, and F. Korte. 1984. Long-term effects of the herbicides atrazine and dichlobenil upon the phytoplankton density and physico-chemical conditions in compartments of a freshwater pond. Chemosphere 13 821-832. 

Somewhat in contrast, there are considerable data concerning the relatively long-term effects of exposure to toxic materials, where there are irritation, tumorigenic, reproductive, or mutation consequences (National Institute for Occupational Safety and Health, Registry of Toxic Effects of Chemical Substances, 1983). In the... 

Relative insensitivity of epidemiologic studies in detecting long-term effects of low-level chemical exposures. 

Research interest in POPs appears to be a relatively recent phenomenon with a dramatic increase in the POPs related publications since 1993. Despite a significant number of research studies most of this is limited to studies of field exposure and analytical methods with few studies on risk assessment, alternatives to POPs or management and disposal techniques. Some participants pointed out that there have been few studies in China assessing the long-term effects of POPs on people or critical ecosystems, studies that would be particularly useful for decisionmakers and for increasing public awareness of the problems posed by such chemicals. 

Holcombe, G.W., Benoit, D.A., Hammermeister, D.E., Leonard, E.N., andjohnson, R.D. Acute and long-term effects of nine chemicals on the Japanese medaka Oryzlas latlped), Arch. Environ. Contam. Toxicol, 28(3) 287-297, 1995. 

EHC monographs examine the physical and chemical properties and analytical methods sources of environmental and industrial exposure and environmental transport kinetics and meta-bohsm including absorption, distribution, transformation, and elimination short- and long-term effects on animals, carcinogenicity, mutagenicity, and teratogenicity and finally, an evaluation of risks for human health and the effects on the environment. 

In some species, however, e.g. ash, Fraxinus excelsior, cells of the traumatic axial parenchyma of the compartmentalization wall 4 may show no evidence of cell wall alterations, yet appear to act normally as a functional barrier to decay (Pearce, R.B., unpublished data). It is to be presumed that the spread of decay fungi is arrested either by chemical defences or by environmental constraints (cf. 26-28) in such species. Clearly, a contribution may be made by these defences in suberizing species also phytoalexin-like antifungal compounds have been detected in association with a suberized wall 4 barrier in Acer saccharinum (42). More work will be required to elucidate the long-term effectiveness of the various mechanisms maintaining the function of these barrier walls. 

Both ayahuasca and ibogaine contain natural MAO inhibitors as a result, the mind-altering compounds are not inactivated so quickly. No one is sure why the plants create the psychoactive compounds. Perhaps the chemicals keep away insects or plant-eating animals. Perhaps they attract plant eaters who seek mind-alteration and thus eat the plant and spread the seeds in their feces. People who have just one strong dose of ibogaine can go for many weeks with very little sleep, and scientists wonder how a drug that exits the system rather quickly can exert such a long-term effect. 

In 1982, the Committee reported (Volume 1) on possible long-term effects of two pharmacologic classes of chemicals... 

Data on the Irritants are insufficient to evaluate their mutagenicity, carcinogenicity, or other long-term effects. Tests of all theses chemicals involved few exposures and low doses. 

Appendix B reviews some important animal studies of cholinesterase reactivator chemicals. The extensive literature reviewed offers little definitive information with which to project possible long-term effects or delayed sequelae in human subjects tested at Edgewood. These compounds have a short biologic half-life of 1 to 3 h. However, no chronic studies were found. Consequently, the carcinogenic potential of cholinesterase reactivators remains... 

Because information on possible long-term effects of the other irritant chemicals used in the Edgewood tests is sparse, this chapter focuses on the effects of mustard gas and two lacrimators, CS and CN. Information on the potential long-term adverse effects of these chemicals is derived from several sources first, observation of long-term disabilities in soldiers who were exposed to a single (in most cases) toxic concentration of irritant during World War I and in persons exposed in peacetime accidents or riot-control procedures second, studies of morbidity in workers chronically exposed to chemical irritants during their manufacture and third, studies in which experimental laboratory animals were exposed to selected chemicals by topical application, injection, or aerosol inhalation. 

Given the available Information on CHT and on the Edgewood subjects exposed to the chemical, long-term health effects of the exposure on the subjects are difficult to predict. 

In general, the Committee found insufficient evidence to evaluate these chemicals, except mustard gas. Mustard gas 1b an experimental mutagen and human carcinogen at high doses. Data on the other irritants are insufficient to evaluate their mutagenicity, carcinogenicity, or other long-term effects. Tests of all these chemicals involved few exposures and low doses. 

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