Double Fatal Inhalation of Dichloromethane

1 Two cases of lethal poisoning following acute inhalation of extremely high concentrations of dichloromethane (DCM) are reported. The concentrations of the solvent found in the blood of the two subjects collected at autopsy and analysed by gas chromatography/ mass spectrometry (572 and 601 mg 1-1) were compatible with those measured in the air a few hours after the discovery of the bodies (up to 168,000 ppm).

2 Extensive brain and lung oedema and congestion, microhaemorrhagic changes of the stomach and congestion in other organs were observed on macroscopic and microscopic examination of both subjects. In addition, and in both cases, high but not lethal carboxyhaemoglobin (COHb) levels (30%) were found in the blood collected at autopsy.

3 Narcosis and respiratory depression due to the effect of DCM on the central nervous system (CNS) appear to have played a critical role in the death of the two men. However, biotransformation of the solvent to toxic metabolites, including carbon monoxide (via oxidative dehalogenation by the cytochrome P450-dependent mixed function oxidase system) or formaldehyde, formic acid, inorganic chloride and carbon dioxide (via the glutathione-S-transferase pathway) may have also contributed significantly to fatal toxicity.

[Polluting agents and sources of urban air pollution]

This paper is an up-to-date review of the scientific evidence on mechanisms of pollutant generation and health effects for a number of urban air pollutants. The review focuses on main sources and health effect of ozone and photochemical smog, benzene, polycyclic aromatic hydrocarbons, and particulate matter. These agents are "priority pollutants", generated by vehicle traffic, and their regulation is currently being examined by the European Council and the European Commission. The aim is to reach, by the year 2010, values lower than 180 micrograms/m3 for ozone as maximum hourly concentration, 2.5 micrograms/m3 for benzene as an annual average, 93 micrograms/m3 for nitrogen dioxide as 98 degrees percentile of hourly concentrations, 50 micrograms/m3 for particulate as a daily average. The goal can be achieved only by means of immediate interventions on emissions.

[Diffusion sampling of benzene present in the urine]

Benzene is a widely diffuse solvent; in the industrial environment benzene is currently present at concentrations of ppm. A valid method of biological monitoring that is easy to perform is need for assessing occupational and non-occupational exposures. A new method has been developed to evaluate low concentrations of benzene in urine samples by means of a diffusion sampling. The solvent is absorbed from the urine surface and concentrated on an absorbent substrate (Tenax) that is placed inside the vial. The solvent is thermically desorbed from Tenax and injected into a column (Thermal Tube Desorber-Supelco; 250 degrees C thermal flash; borosilicate capillary glass-column SPB-I 60 m length, 0.75 mm I.D., 1 micron film thickness; GC Dani 8580-FID). The method, which had not been previously employed for the determination of volatile organic substances in biological fluids, has a linear range which extends up to 40 micrograms/l, and gives results in excellent agreement with the conventional Head Space method, except in the low concentration region: the new method permits the quantitative determination of benzene quantities smaller than the detection limit of Head Space method connected with mass spectrometer (approximately 1 microgram/l). The detection limit was not exactly determined, but is estimated to be of 100 ng/l with 25 ml of urine sample.

[Environmental impact of tanning industry]

Airborne hydrogen sulphide was monitored continuously for 91 hours in the residential area of the Chiampo Valley in northern Italy, where about 150 tanneries are located; 74 air samples were taken to detect the environmental concentrations of solvents. Hydrogen sulphide concentrations obtained every 2.5 min in the residential area of Arzignano, the main town in the Chiampo Valley, were averaged over one hour. The mean values were plotted against time and wind direction: the tridimensional plot showed that the highest concentrations (over 300 ppb) were statistically detected between 10 a.m. and 12 a.m. with an east-southeast wind direction. About 40 tanneries are located over a distance of 1 km along this direction. The main causes of air pollution were the discharge of unhairing liquid and pickling operations in the factories, and the sewage system and waste water treatment plant. As regards solvents, a preliminary study showed that the 149 tanneries located in this area used about 17,700 tons/year of coating materials to finish about 40 million square metres of leather. Thirty more solvents were released into the atmosphere from these materials, the most important of which being: aromatic hydrocarbons (3,100 tons/year), acetates (2,800 tons/year), ketones (1,500 tons/year), alcohols (1,350 tons/year) and glycol ethers (520 tons/years). The average concentrations detected in the air were: 326 micrograms/m3 for aromatic hydrocarbons, 302 micrograms/m3 for acetates, 139 micrograms/m3 for ketones, 125 micrograms/m3 for alcohols and 16 micrograms/m3 for glycol-ethers. The cumulative concentration was more than 1 mg/m3 for 30% of the samples and more than 2 mg/m3 for 7%. The percentage of airborne solvents agreed well with that of solvents in the coating materials, thus demonstrating that most of these compounds originated from the tanneries.

Identification of the n-heptane metabolites in rat and human urine

Numerous n-heptane metabolites have been identified and quantified by gas chromatography and mass spectrometry in some tissues and in the urine of Sprague Dawley rats exposed for 6 h to 1800 ppm n-heptane. 2-Heptanol and 3-heptanol were the main biotransformation products of the solvent. 2-Heptanone, 3-heptanone, 4-heptanol, 2,5-heptanedione, gamma-valerolactone, 2-ethyl-5-methyl-2,3-dihydrofuran and 2,6-dimethyl-2,5-dihydropyran were also found as metabolites of n-heptane. In five shoe factory workers and in three rubber factory workers the mean exposure to technical heptane was measured (n-heptane ranged between 5 and 196 mg/m3). In the urine collected at the end of their work shift some n-heptane biotransformation products were found: 2-heptanol, 3-heptanol, 2-heptanone, 4-heptanone and 2,5-heptanedione. 2-Heptanol was the main n-heptane metabolite and its urinary concentrations ranged between 0.1 and 1.9 mg/l. Urinary 2,5-heptanedione was detectable only in some samples and at very low concentration (0.1-0.4 mg/l). These data suggest that n-heptane can be considered as a neurotoxic product, since it gives rise to 2,5-heptanedione, but the small amount of the urinary metabolite is very unlikely to cause clinical damage to the peripheral nervous system.

Methyl ethyl ketone exposure in industrial workers. Uptake and kinetics

Exposure to methyl ethyl ketone (MEK) was studied in workers occupationally exposed in industrial workplaces. Alveolar concentrations of MEK were compared with environmental exposure and with blood MEK concentrations. Urinary excretion of MEK and its metabolite, acetylmethylcarbinol , were compared with environmental exposure. The solubility of MEK was also studied in human body tissues which allowed us to estimate the distribution and kinetics of MEK by means of data computing on a multicompartimental mathematic model. The alveolar MEK concentration was correlated with the environmental MEK concentration and corresponded to 30% of it. Blood MEK concentration was correlated with alveolar MEK concentration and corresponded to 104-116 times the alveolar concentration and 31-35 times the environmental concentration. Urinary MEK excretion was correlated with environmental MEK exposure and the urinary excretion of acetylmethylcarbinol . The mean urinary MEK concentration was 4.8 times the mean environmental MEK concentration. The MEK solubility in the human tissues (brain, kidney, lung, fat, heart, muscles and liver) turned out to be similar to that found in blood (blood/air = 183). The amount of MEK and its metabolite, acetylmethylcarbinol , eliminated by the kidney corresponded together to 0.1% of the alveolar MEK uptake.

Rubber manufacture: sampling and identification of volatile pollutants

Volatile pollutants produced from several rubber goods manufacturing processes were sampled and analyzed. Samples were collected in the vulcanization areas of a shoe-sole factory, a tire retreading operation, and also in the extrusion areas of the retreading operation and an insulated cable manufacturer. Volatile organics from the vulcanization and extrusion operations were collected on activated charcoal, desorbed with trichlorofluoromethane and analyzed by GC/MS. Approximately 100 different compounds were identified and quantitated; their cumulative concentrations ranged from 25 to 27000 micrograms/cubic meter.

[Sampling of solvents on active charcoal: chemical and thermal recovery]

The problems relating to the sampling of solvents on active charcoal and their recovery by chemical and thermal desorption are pointed out. The experimental values of breakthrough volumes for a number of compounds are reported, together with their extent of recovery by carbon disulfide extraction and by thermal desorption under inert gas flow. Thermal desorption, when carried out under the proper conditions, including the use of a temperature program, leads to quantitative recovery for most industrial solvents.

Occupational styrene exposure: environmental and biological monitoring

Occupational exposure to styrene was studied by environmental and biological monitoring in 22 workers employed in a fiberglass reinforced plastic factory. The mean environmental styrene concentration in individual workplaces ranged from 120 to 684 microliter/l. Blood styrene, which was tested at the end of the work shift, ranged from 450 to 3700 micrograms/l. Urinary mandelic and phenylglyoxylic acid, which were determined at the end of the work shift, ranged from 133 to 2100 and from 107 to 685 mg/l, respectively. Environmental styrene exposure was better correlated with styrenemia than with mandelicuria and phenylglyoxylicuria considered either individually or together. The ratio between environmental and blood styrene showed that styrenemia was, on average, 3.3-4.9 times higher than environmental styrene concentration.

Purge and Trap analysis of toluene in blood: comparison with the Head Space method

A procedure for the determination of toluene in blood by the Purge and Trap method is described. The method, which had not been previously employed for the determination of volatile organic substances in biological fluids, has a linear range which extends up to at least 1500 micrograms/L, and gives results in excellent agreement with the conventional Head Space method; the detection limit was not exactly determined, but is estimated to be less than 7.5 micrograms/L, much better than for the Head Space method. Using the Purge and Trap method, we have observed the accumulation of toluene in the blood of experimental subjects as a result of a weekly exposure to toluene.

Biomonitoring of occupational toluene exposure

Toluene exposure was studied in 20 workers employed in painting and hand-finishing in an art furniture factory. Toluene was determined in the environmental air of places of work and in the alveolar air and blood of the workers. Hippuric acid and cresols were also tested in the workers' urine. Blood and urine tests were carried out before the work shift on Monday and Friday morning and at the end of the work shift on Friday afternoon. The other tests were performed on Friday afternoon only. Alveolar toluene concentrations, which were significantly correlated with environmental toluene concentrations (r = 0.6230; P less than 0.01), corresponded to 19.4% of the toluene concentration in the atmosphere. Blood toluene was also found in painters on Monday morning and was significantly correlated with the other parameters. On Friday afternoon it was three times higher than the environmental toluene concentration. Urinary o-Cresol was highly correlated with toluene in the atmosphere, in blood and with hippuric acid in urine. On the basis of the slope of the regression line the ratio between urinary o-Cresol and blood toluene concentration was 0.99. At the end of the work shift urinary hippuric acid concentration was highly correlated with o-Cresoluria and with toluene in blood and in the atmosphere.