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2136. Pyrolysis products of PVC and polystyrene
450
THE CHEMICAL ENVIRONMENT
glass dust found in the survey were well below the proposed TLV of 15 mg/m 3. Compared with asbestos fibres in industrial plants, the concentration of respirable glass fibres was much lower, and there was no evidence that glass fibres had any action other than mechanical irritation of the upper respiratory tract.
2135. Estimation of inhaled glue constituents Collom, W. D. & Winek, C. L. (1970). Detection of glue constituents in fatalities due to "glue sniffing". Clin. Toxicol. 3, 125. This paper presents the methods used for identifying and estimating the benzene and toluene present in two boys who died as a result of inhaling vapours from model-aeroplane cements. One case involved a 16-year-old male, a chronic 'glue-sniffer', whose death was attributed to the inhalation of benzene vapours from rubber cement. The concentrations of benzene in the blood and kidney at the time of analysis were 94/zg/100 ml and 550/~g/100 g, respectively. The second case involved the death of a 13-year-old male from respiratory arrest due to a combination of narcosis and suffocation. The boy had a prior history of 'glue sniffing' and was found with a plastic bag, containing the residue from model aeroplane glue, over his head. The concentrations of toluene per I00 g tissue were 1.1 mg in blood, 4.7 mg in liver, 3-9 mg in kidney and 4-4 mg in brain. The procedure used involved extracting steam distillates of tissue slurries and blood with cyclohexane for spectrophotometric scanning from 220 to 370 m/~. Tissue slurries and blood were either used directly for quantitative analysis by gas chromatography or treated with sulphuric and nitric acids by the method of Freimuth to nitrate the toluene and benzene. The nitration products were then extracted from the diluted acid mixture with I : 10 (v/v) cyclohexane. Quantitative analysis of the materials was carried out either by the headspace or by the direct-injection method, the latter having a sensitivity in this study of about 2 mg/100 g for benzene and approximately 5 mg/100 g for toluene. The very low concentrations encountered, particularly in the case involving benzene, necessitated the use of the headspace method. It was recognized that the actual concentrations of benzene and toluene at the time of death would have been higher than those found, because of their volatility and their absorption by rubber and other packaging materials. 2136. Pyrolysis products of PVC and polystyrene Le Moan, G. & Chaigneau, M. (1969). t~tude de la pyrolyse de mat6riaux en mati6res plastiques. I.--Polychlorure de vinyle (P.V.C.). Caract6risation d'6ventuels compos6s toxiques volatils. Annls pharm, fr. 27, 97. Le Moan, G. & Chaigneau, M. (1970). l~tude de la pyrolyse de mat6riaux en mati6res plastiques. II.--Polychlorure de vinyle (P.V.C.). Caract6risation de compos6s condensables. Annls pharm, fr. 28, 39. Chaigneau, M. & Le Moan, G. (1970). l~tude de la pyrolyse de mat6riaux en mati6res plastiques. III.--Polystyr6nes Annls pharm, fr. 28, 41. The first two studies cited above were carried out in an attempt to identify the pyrolysis products of polyvinyl chloride (PVC). When samples of PVC (containing about 70 polymer and various additives) were heated in air, carbon dioxide or carbon monoxide (with or without water) for l hr at a range of temperatures between 100 and 400°C, it was found that decomposition occurred around 150-200°C, when the materials began to smoulder and darken. This was followed by the appearance of a rose-coloured liquid and,
THE CHEMICAL ENVIRONMENT
451
at higher temperatures still, a white liquid which crystallized on cooling. When water was present a number of white crystals formed. The major volatile pyrolysis product was identified as hydrogen chloride, but depending on the temperature, traces of a number of other materials were found, including hydrogen, various aliphatic hydrocarbons, benzene, toluene and methyl and ethyl chlorides. No chlorine compounds were found in the condensates formed by heating these samples or another containing only 0.25~ additives at 400°C. Various cyclic hydrocarbons were identified, however, as well as phthalic acid and anhydride, benzaldehyde and acetophenone, and, in some cases, derivatives of benzanthracene or benzophenanthrene. In the third study cited above, the authors turned their attention to polystyrene. In oxygen, decomposition took place around 300°C, carbon monoxide and carbon dioxide being the chief volatile products found. Traces (more clearly defined at 500°C) of a number of other materials, such as various aliphatic, cyclic and polycyclic hydrocarbons and oxidation products, chiefly acetophenone, were also identified. When heated in carbon dioxide or carbon monoxide, polystyrene was not decomposed until around 500°C. The condensates proved to be a very complex mixture of compounds. In addition to the mono-, di- and trimers of styrene already reported by various authors, phenylacetylene, phenylnaphthalene and triphenylbenzene were prominent among the products identified. 2137. The target for silica particles Nadler, S. & Goldfischer, S. (1970). The intracellular release of lysosomal contents in macrophages that have ingested silica. J. Histochem. Cytochem. 18, 368. Silicosis ('miners' lung') has been recognized for many years as an important occupational hazard in mining industries. Macrophages are an important histological feature of the early silicosis granuloma, the formation of which leads to extensive and crippling pulmonary fibrosis. Macrophages in the lung ingest inhaled silica particles and are killed. They are then replaced by fibrotic tissue which is responsible for the crippling impairment of oxygen uptake in the lung. In 1966, Allison et al. (J. exp. Med. 1966, 124, 141) suggested an explanation for the inability of the macrophages to survive ingestion of silica particles as they survive their removal of other foreign particles. It was proposed that silica particles can interfere with the membranes of the lysosomes into which they are incorporated within the macrophages (Cited in F.C.T. 1968, 6, 779) thus allowing digestive enzymes to leak out and destroy the cell. Lysosomal leakage into the cytoplasm has been implicated not only in silicosis but also in such diverse phenomena as carcinogenesis (Allison & Malluci, Nature, Lond. 1964, 203, 1024) and rheumatoid arthritis (Weissman, Arthritis Rheum. 1966, 9, 834). The work of Allison et al. (loc. cit.) was based on a histochemical staining method for the visualization of the enzyme, acid phosphatase, leaking from the silica-damaged lysosomes. The authors of the paper cited above criticize this use of the Gomori acid-phosphatase staining technique on the grounds that the method is not without diffusion artefacts even in untreated cells, and also because the effect of silica on the histochemical reaction, which involves the precipitation of lead phosphate, is unknown. They describe their own use of the peroxidase-diaminobenzidine (DAB) reaction, which as a lysosomal marker has been shown to be free from significant diffusion. The peroxidase-DAB reaction of untreated mouse peritoneal macrophages was compared with that of macrophages treated with 2-5 tz particles of silica or diamond dust. Dead or dying macrophages with diffuse enzyme staining, indicating lysosomal leakage, were seen as
THE CHEMICAL ENVIRONMENT
glass dust found in the survey were well below the proposed TLV of 15 mg/m 3. Compared with asbestos fibres in industrial plants, the concentration of respirable glass fibres was much lower, and there was no evidence that glass fibres had any action other than mechanical irritation of the upper respiratory tract.
2135. Estimation of inhaled glue constituents Collom, W. D. & Winek, C. L. (1970). Detection of glue constituents in fatalities due to "glue sniffing". Clin. Toxicol. 3, 125. This paper presents the methods used for identifying and estimating the benzene and toluene present in two boys who died as a result of inhaling vapours from model-aeroplane cements. One case involved a 16-year-old male, a chronic 'glue-sniffer', whose death was attributed to the inhalation of benzene vapours from rubber cement. The concentrations of benzene in the blood and kidney at the time of analysis were 94/zg/100 ml and 550/~g/100 g, respectively. The second case involved the death of a 13-year-old male from respiratory arrest due to a combination of narcosis and suffocation. The boy had a prior history of 'glue sniffing' and was found with a plastic bag, containing the residue from model aeroplane glue, over his head. The concentrations of toluene per I00 g tissue were 1.1 mg in blood, 4.7 mg in liver, 3-9 mg in kidney and 4-4 mg in brain. The procedure used involved extracting steam distillates of tissue slurries and blood with cyclohexane for spectrophotometric scanning from 220 to 370 m/~. Tissue slurries and blood were either used directly for quantitative analysis by gas chromatography or treated with sulphuric and nitric acids by the method of Freimuth to nitrate the toluene and benzene. The nitration products were then extracted from the diluted acid mixture with I : 10 (v/v) cyclohexane. Quantitative analysis of the materials was carried out either by the headspace or by the direct-injection method, the latter having a sensitivity in this study of about 2 mg/100 g for benzene and approximately 5 mg/100 g for toluene. The very low concentrations encountered, particularly in the case involving benzene, necessitated the use of the headspace method. It was recognized that the actual concentrations of benzene and toluene at the time of death would have been higher than those found, because of their volatility and their absorption by rubber and other packaging materials. 2136. Pyrolysis products of PVC and polystyrene Le Moan, G. & Chaigneau, M. (1969). t~tude de la pyrolyse de mat6riaux en mati6res plastiques. I.--Polychlorure de vinyle (P.V.C.). Caract6risation d'6ventuels compos6s toxiques volatils. Annls pharm, fr. 27, 97. Le Moan, G. & Chaigneau, M. (1970). l~tude de la pyrolyse de mat6riaux en mati6res plastiques. II.--Polychlorure de vinyle (P.V.C.). Caract6risation de compos6s condensables. Annls pharm, fr. 28, 39. Chaigneau, M. & Le Moan, G. (1970). l~tude de la pyrolyse de mat6riaux en mati6res plastiques. III.--Polystyr6nes Annls pharm, fr. 28, 41. The first two studies cited above were carried out in an attempt to identify the pyrolysis products of polyvinyl chloride (PVC). When samples of PVC (containing about 70 polymer and various additives) were heated in air, carbon dioxide or carbon monoxide (with or without water) for l hr at a range of temperatures between 100 and 400°C, it was found that decomposition occurred around 150-200°C, when the materials began to smoulder and darken. This was followed by the appearance of a rose-coloured liquid and,
THE CHEMICAL ENVIRONMENT
451
at higher temperatures still, a white liquid which crystallized on cooling. When water was present a number of white crystals formed. The major volatile pyrolysis product was identified as hydrogen chloride, but depending on the temperature, traces of a number of other materials were found, including hydrogen, various aliphatic hydrocarbons, benzene, toluene and methyl and ethyl chlorides. No chlorine compounds were found in the condensates formed by heating these samples or another containing only 0.25~ additives at 400°C. Various cyclic hydrocarbons were identified, however, as well as phthalic acid and anhydride, benzaldehyde and acetophenone, and, in some cases, derivatives of benzanthracene or benzophenanthrene. In the third study cited above, the authors turned their attention to polystyrene. In oxygen, decomposition took place around 300°C, carbon monoxide and carbon dioxide being the chief volatile products found. Traces (more clearly defined at 500°C) of a number of other materials, such as various aliphatic, cyclic and polycyclic hydrocarbons and oxidation products, chiefly acetophenone, were also identified. When heated in carbon dioxide or carbon monoxide, polystyrene was not decomposed until around 500°C. The condensates proved to be a very complex mixture of compounds. In addition to the mono-, di- and trimers of styrene already reported by various authors, phenylacetylene, phenylnaphthalene and triphenylbenzene were prominent among the products identified. 2137. The target for silica particles Nadler, S. & Goldfischer, S. (1970). The intracellular release of lysosomal contents in macrophages that have ingested silica. J. Histochem. Cytochem. 18, 368. Silicosis ('miners' lung') has been recognized for many years as an important occupational hazard in mining industries. Macrophages are an important histological feature of the early silicosis granuloma, the formation of which leads to extensive and crippling pulmonary fibrosis. Macrophages in the lung ingest inhaled silica particles and are killed. They are then replaced by fibrotic tissue which is responsible for the crippling impairment of oxygen uptake in the lung. In 1966, Allison et al. (J. exp. Med. 1966, 124, 141) suggested an explanation for the inability of the macrophages to survive ingestion of silica particles as they survive their removal of other foreign particles. It was proposed that silica particles can interfere with the membranes of the lysosomes into which they are incorporated within the macrophages (Cited in F.C.T. 1968, 6, 779) thus allowing digestive enzymes to leak out and destroy the cell. Lysosomal leakage into the cytoplasm has been implicated not only in silicosis but also in such diverse phenomena as carcinogenesis (Allison & Malluci, Nature, Lond. 1964, 203, 1024) and rheumatoid arthritis (Weissman, Arthritis Rheum. 1966, 9, 834). The work of Allison et al. (loc. cit.) was based on a histochemical staining method for the visualization of the enzyme, acid phosphatase, leaking from the silica-damaged lysosomes. The authors of the paper cited above criticize this use of the Gomori acid-phosphatase staining technique on the grounds that the method is not without diffusion artefacts even in untreated cells, and also because the effect of silica on the histochemical reaction, which involves the precipitation of lead phosphate, is unknown. They describe their own use of the peroxidase-diaminobenzidine (DAB) reaction, which as a lysosomal marker has been shown to be free from significant diffusion. The peroxidase-DAB reaction of untreated mouse peritoneal macrophages was compared with that of macrophages treated with 2-5 tz particles of silica or diamond dust. Dead or dying macrophages with diffuse enzyme staining, indicating lysosomal leakage, were seen as