Solvents chronic

Repeated or prolonged inhalation may cause mucous irritation. Repeated or prolonged contact may cause defatting and drying of the skin. MIK is known to enhance the neurotoxicity of linear six-carbon solvents. Chronic exposure may cause axonal neuropathy, paresthesia, muscle weakness, and kidney damage. 

A number of antioxidants have been accepted by the FDA as indirect additives for polymers used in food appHcations. Acceptance is deterrnined by subchronic or chronic toxicity in more than one animal species and by the concentration expected in the diet, based on the amount of the additive extracted from the polymer by typical foods or solvents that simulate food in their extractive effects. Only materials of insignificant risk to the consumer are regulated by the FDA for use in plastics contacted by food stuffs. 

Dichloroethane is one of the more toxic chlorinated solvents by inhalation (49). The highest nontoxic vapor concentrations in chronic exposure studies with various animals range from 100 to 200 ppm (50,51). 1,2-Dichloroethane exhibits a low single-dose oral toxicity in rats LD q is 680 mg/kg (49). Repeated skin contact should be avoided since the solvent can cause defatting of the skin, severe irritation, and moderate edema. Eye contact may have slight to severe effects. 

Dichloroethylene is toxic by inhalation and ingestion and can be absorbed by the skin. It has a TLV of 200 ppm (10). The odor does not provide adequate warning of dangerously high vapor concentrations. Thorough ventilation is essential whenever the solvent is used for both worker exposure and flammabihty concerns. Symptoms of exposure include narcosis, dizziness, and drowsiness. Currently no data are available on the chronic effects of exposure to low vapor concentrations over extended periods of time. 

In a cross-sectional study, exposure and effect are studied simultaneously. This approach contains an inherent problem because exposure must precede the effect. However, it can he used to investigate acute effects and also mild chronic effects (which do not force people to leave their jobs) if exposure has remained rather stable for a long time. When the prevalence of the effects studied are compared with the prevalence in other worker groups (controls or references) which correspond otherwise with the study group but are not exposed to the agent investigated, indicative evidence of possible causality may be obtained. For example, cross-sectional studies have been applied successfully to reveal the associations between mild neurotoxic effects and exposure to organic solvents. ... 

At one time, benzene was widely used as a solvent, both commercially and in research and teaching laboratories. Its use for that purpose has largely been abandoned because of its toxicity. Chronic exposure to benzene vapor leads to various blood disorders and, in extreme cases,... 

Tolerance is characterized by reduced responsiveness to the initial effects of a drug after repeated exposure or reduced responsiveness to a related compound (i.e., cross-tolerance). Animal studies have not provided conclusive evidence of tolerance to the effects of the centrally active compounds in toluene or trichloroethane (Moser and Balster 1981 Moser et al. 1985). Observations in humans, on the other hand, have documented pronounced tolerance among subjects who chronically inhale substances with high concentrations of toluene (Glaser and Massengale 1962 Press and Done 1967) and butane (Evans and Raistrick 1987). Kono et al. (2001) showed that tolerance to the reinforcing effects of solvents is comparable to that conditioned by nicotine but less intense than that reported with alcohol or methamphetamine use. 

Himnan DJ Tolerance and reverse tolerance to toluene inhalation effects on open-field behavior. Pharmacol Biochem Behav 21 625-631, 1984 Hinman DJ Biphasic dose-response relationship for effects of toluene inhalation on locomotor activity. Pharmacol Biochem Behav 26 65-69, 1987 Hormes JT, Filley CM, Rosenberg NL Neurologic sequelae of chronic solvent vapor abuse. Neurology 36 698—702, 1986... 

Respiratory Effects. One study suggested increased respiratory disorders (asthma, bronchitis, pneumonia) in children with chronic exposure to a solvent-contaminated water supply (Byers et al. 1988). Two municipal wells in eastern Woburn, Massachusetts, were found to contain several solvents including trichloroethylene (267 ppb) and tetrachloroethylene (21 ppb). The increased susceptibility to infection may be secondary to effects on the immune system. Accurate chemical-specific exposure levels for individuals could not be determined because the water distribution system was designed to use water from different wells at different rates and times. Other limitations of this study are described in Section 2.2.2.8. 

Rapid dermal absorption of trichloroethylene is evident from a study in which peak blood and exhaled air concentrations occurred within 5 minutes after a human subject immersed one hand in a solution of unspecified trichloroethylene concentration for 30 minutes (Sato and Nakajima 1978). Studies on dermal absorption of trichloroethylene in humans, as well as animals, are complicated by the fact that exposure in these studies is usually by direct contact of the skin with the undiluted chemical. Trichloroethylene is a lipophilic solvent that defats the skin and disrupts the stratum comeum, thereby enhancing its own absorption. Thus, the rate of absorption probably increases in a nonlinear fashion with greater epidermal disruption. Although the extent of absorption through the skin may be relatively modest with normal industrial use (Sato and Nakajima 1978 Stewart and Dodd 1964), there is insufficient information to evaluate the effects of chronic, low-level exposure in hiunans, especially when multiple routes may be involved. 

Byers VS, Levin AS, Ozonoff DM, et al. 1988. Association between clinical symptoms and lymphocyte abnormalities in a population with chronic domestic exposure to industrial solvent-contaminated domestic water supply and a high incidence of leukemia. Cancer Immunol Immunother 27 77-81. 

Rasmussen K, Jeppesen HJ, Sabroe S. 1993d. Solvent-induced chronic toxic encephalopathy. AmJlnd Med 23 779-792. 

Choice of Solvent. As indicated by Averell and Norris (1), and independently confirmed by the authors, technical benzene is a superior stripping solvent for parathion residues. It is almost completely miscible with technical grade parathion at room temperatures, it is universally available and low in cost, it is readily volatile, it fails to contribute to storage decomposition (6), it is a good solvent for plant oils and waxes, and it is immiscible with water. On the other hand, benzene is highly flammable and its vapors are very toxic to human beings, especially as a chronic toxicant even in small doses. 

Environmentally Induced Illnesses Ethics, Risk Assessment and Human Rights. Thomas Kerns, Jefferson, NC McFarland, [in press]. Addresses the ethics of managing environmental health and ubiquitous toxicants (such as solvents, pesticides and artificial fragrances). The work includes recent medical literature on chronic health effects from exposure to toxicants and the social costs of these disorders relevant historic and human rights documents recommendations for public policy and legislation and primary obstacles faced by public health advocates. 

Table 7-2 lists some of the more common solvents, along with some of their effects and their hazard potential. The word acute in the table refers to a short-term, relatively high concentration exposure, while the term chronic refers to a long-term, relatively low exposure. The column labeled Hazard Potential gives the recommended exposure limit. A question mark after a comment indicates that there is some doubt about the conclusion. 

So-called peripheral neuropathies can result from excessive exposure to certain industrial solvents such as carbon disulfide (CS2, used in the rubber and rayon industries) and hexane (CgHn, once used in certain glues and cleaning fluids). Over-exposure to acrylamide, an important industrial chemical, and chronic alcohol abuse can also induce this effect. As the name implies, it involves attack of the chemical on and damage to axonal portions of neurons. Typical symptoms of peripheral neuropathies include weakness or numbness in the limbs, which are more or less reversible depending upon the specific agent and the intensity of exposure. 

Environment and health-related problems are especially determined by health risks due to solvents, which result in damage to skin and the central nervons system (polyneuropathy, encephalopathy) in the case of chronic exposure. Some solvents are also classified as being carcinogenic (e.g. benzene, trichloroethylene) or are suspected of being carcinogenic (e.g. perchloroethylene) or reproduction-toxic (e.g. toluene). 

Sohnlein B, Letzel S, Weltle D, et al Occupational chronic exposure to organic solvents XIV. Examinations concerning the evaluation limit value for 2-ethoxyethanol and 2-ethoxyethyl acetate and the genotoxic effects of these glycol ethers. Int Arch Occup Environ Health 64 479-484, 1993... 

Chronic exposure to commercial hexane solvent (51 % w-hexane) at concentrations up to 9000ppm was not carcinogenic to F-344 rats or to male B6C3F1 mice but did result in an increased incidence of liver tumors in female mice. It is unclear what components of the hexane mixture caused the neoplasms. ... 

Daughtrey W, Newton P, Rhoden R, et ah Chronic inhalation carcinogenicity study of commercial hexane solvent in F-344 rats and B6C3F1 mice. Toxicol Sci 48(l) 21-29, 1999... 

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