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Results for “METHYL CHLORIDE”

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At least 145 records · Page 8Linked to original sources
PubMed2003

Chloride methylation by plant pectin: an efficient environmentally significant process.

Atmospheric chloromethane (CH3Cl) plays an important role in stratospheric ozone destruction, but many uncertainties exist regarding the strengths of its sources and sinks and particularly regarding the processes generating this naturally occurring gas. Evidence is presented here that CH3Cl is produced in many terrestrial environments by a common mechanism. Abiotic conversion of chloride to CH3Cl occurs readily in plant material, with the widespread plant component pectin acting as a methyl donor. Significant CH3Cl emissions from senescent and dead leaves were observed at ambient temperatures; those emissions rose dramatically when temperatures increased. This ubiquitous process acting in terrestrial ecosystems and during biomass burning could contribute the bulk of atmospheric CH3Cl.

Atmosphere↗
PubMed1985

Pharmacokinetics of inhaled methyl chloride (CH3Cl) in male volunteers.

Six volunteers, 25-41 years of age, were exposed for 6 hr on separate days to 50 and 10 ppm of CH3Cl. Blood and expired air CH3Cl concentrations reached an apparent plateau during the first hour of the exposure and were proportional to the exposure concentration. Consistent with previous reports, the volunteers could be separated into two discrete groups based on the differences observed in their blood and expired air CH3Cl concentrations. Both groups eliminated CH3Cl rapidly once the exposure was terminated, but CH3Cl was eliminated more rapidly by those volunteers with the lower blood and expired air CH3Cl concentrations. The existence of these two groups can be explained by a twofold difference in the rate at which they metabolized CH3Cl; however, this difference is of questionable toxicological significance. Urinary excretion of the putative metabolite S-methyl cysteine was not related to the exposure; thus, it is not a valid means of monitoring occupational exposure to CH3Cl.

Adult↗
PubMed1992

Exposures to polyvinyl chloride, methyl ketone and other chemicals. The pulmonary and non-pulmonary effect.

As part of the continuing assessment of the health impact of exposures in the emerging industries of Nigeria, a study was conducted to determine the relative impact of exposures encountered in four operations of a shoe factory. The health impact assessment consisted of spirometric lung function evaluations and environmental measurement for polyvinyl chloride (1.6 +/- 5 ppm). The study showed that there were differences among exposure subgroups with respect to pulmonary, neurological and dermal toxicities and that these differences were dictated by the types of exposure encountered. Pulmonary toxicity was most severe in the vinyl chloride-exposed subgroup. Neurological impact was most severe in the leather and methylethyl ketone-exposed subgroup and dermal toxicity most severe in the subgroup exposed to plasticizers and stabilizers. There existed substantial deficits in lung function (forced expiratory volume, forced vital capacity FEV1, FVC) among the subgroups relative to normal, non-industrially exposed Nigerians of similar age and height. The deficits in lung function, particularly in FVC, paralleled the variations in the prevalence of restrictive lung disease, which for the whole study group was 56.5 cases per 1000 person-years. The vinyl chloride-exposed subgroup had the highest prevalence of restrictive lung disease, 92.6 cases per 100 person-years. Step-wise multiple regression suggested that 27% of the deficit in FEV1 was explainable by the number of exposures. The use of person-years as a denominator gives a better estimate of risk than the total number of subjects as it incorporates both the number exposed and the total exposure experience.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗
PubMed1983

Mercury chloride--and methyl mercury chloride--induced inhibition in NOR activity.

Previous work has raised the question of whether mercury compounds inhibit the activity of the nucleolar organizing genes. For that reason we performed a cytophotodensitometric analysis on silver-stained interphase nuclei from human peripheral blood lymphocytes exposed to various concentrations of HgCl2 (0-150 X 10(-6) M), CH3HgCl (0-50 X 10(-6) M), and actinomycin D (0-0.1 microgram/ml). The last compound was used as a positive control. The cells were exposed to the compounds either during G1-early S phase, allowing recovery after the exposure, or from G1 until harvest; thus no recovery was allowed in this case. Like actinomycin D, both mercury compounds were shown to inhibit the NOR activity. This inhibition was furthermore more evident during the short exposure experiment. Our results do confirm that mercury compounds may, to a certain extent, influence some factors regulating the nucleolus-organizing activity.

Adult↗
PubMed2005

Dynamical steric effect in the decomposition of methyl chloride on a silicon surface.

We report results of a study on the incident energy and the surface-temperature dependence of the steric effects in the dissociative adsorption of CH3Cl on a Si{100} surface. Data presented here show that the initial sticking probability for the Cl-end collision is larger at an incident energy of 120 meV than that in the CH3-end collision. Furthermore, this steric preference is quite sensitive to the kinetic energy and the rotational state of CH3Cl and the surface temperature. This study shows that the nonequilibrium surface trapping plays a key role in the initial step of the decomposition of CH3Cl on Si{100}.

Journal Article↗