Toxicity, synergism

In their acute toxic effects on the skin and liver PCBs resemble the chlorinated naphthalenes. Acute yellow atrophy is produced in the liver and enhanced in the presence of CHClj (synergism). Toxicity increases with increase in chlorine content of the PCB, and with oxide formation. Skin lesions (chloracne) consist of small pimples and dark pigmentation of exposed areas. Later comedones and pustules develop. With systemic intoxication, progressive symptoms are nausea, vomiting, weight loss, jaundice, edema, abdominal pain, and, where liver damage is severe, it is followed by coma and death (Sax, 3d ed., p. 551). 

We have determined LD50 values of 28 BP analogs for the housefly by injection after pretreatment with pb. The most toxic compound was 3-methyl-4-n-propyl BP (compound 3). Their toxicity was greatly dependent on the nature of the bridgehead substituent. The following equation has been derived by multiple regression analysis of some of those synergized toxicity data for a series of 4-substituted BPs (jJ) ... 

Synergism is appHed to a situation where the effect of two or more chemicals that have common mechanism of toxicity, given together, is significantly greater than that expected from considerations on the toxicity of each material alone. This differs from potentiation in that both materials contribute to the toxic injury, and the net effect is always greater than additive. 

There has been a revival of interest in recent years in antimony mercaptides as alternatives to the organo-tin stabilisers. This stems from the low level of toxicity and the strong synergism with calcium stearate. However, compared to the... 

Jasmolin II in pure form was nearly equal to cinerin II in toxicity to houseflies but much less when synergized. The synergistic factor of the synergized compounds is pyrethrum extract 9.6 jasmolin II, 7.0 cinerin II, 12.0. 

Other cases of potentiation will be discussed in later chapters dealing with individual pollutants. These will include the synergism of pyrethroid toxicity to... 

Synergism Similar to potentiation [q.v.], but some authors use the term in a more restricted way (e.g., where one component of a mixture, the synergist, would not cause toxicity if applied alone at the dose in question). 

Listing gaseous emissions, concentrations, smoke characteristics prevailing winds and exposed zones toxicity or nuisance potential effects of synergism or poor atmospheric dispersing conditions. Consent limits. 

Abstract The characterization of toxicological impact of chemicals and mixtures from environmental matrices is a critical point in the assessment of adverse effects induced in human and ecological targets. In fact, the toxicity of most of the environmental mixtures is still under investigation due to the possibility of synergic or antagonistic effects of the components. Moreover, in some cases, the toxicity of identified chemicals is not already well known and it could be an additional matter of concern. 

PCB 156, a mixed inducer of microsomal enzymes, significantly increases the incidences of cleft palates by 2,3,7,8-TCDD in rodents (Bimbaum et al. 1985). Interactions among polychlorinated congeners may range from antagonism to additivity to synergism (Safe 1990), and the toxicity of individual PCBs can be raised by interaction with other PCBs (Table 24.5). 

A number of studies of the toxicity of zinc oxide/hexachloroethane smoke have been conducted (Brown et al. 1990 Karlsson et al. 1986 Marrs et al. 1983). These studies demonstrate that smoke exposure results in pulmonary inflammation and irritation. When male Porton Wistar rats were exposed to hexachloroethane/zinc oxide smoke for 60 minutes, the lungs showed pulmonary edema, alveolitis, and areas of macrophage infiltration 3 days later. At 14 days, there was interstitial fibrosis and macrophage infiltration. At 28 days, increased fibrosis and macrophage infiltration were noted. However, these same symptoms occurred when the animals inhaled zinc chloride there was no apparent synergism between the zinc chloride and residual hexachloroethane (Brown et al. 1990 Richard et al. 1989). This is consistent with the fact that smoke contains little hexachloroethane and the observation that acute exposure to 260 ppm hexachloroethane had no effects on the lungs of rats (Weeks et al. 1979). 

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