Methanol estimating exposures

An example of a nonoccupational exposure is methanol, which is formed endogenously, probably as the result of the activities of intestinal flora or enzymatic processes. It is present in a number of consumer products. Methanol may be present in low concentrations in some foods, juices, and alcoholic beverages. Methanol can also be derived from the intestinal enzymatic hydrolysis of the artificial sweetener aspartame, which results in methanol absorption from the intestine (Butchko et al. 2002). It is estimated that a 355-mL serving of aspartame-sweetened beverages and of various fruit and tomato juices may contribute about 20-100 mg of dietary methanol (Butchko et al. 2002). For comparison purposes, exposure at the current Threshold Limit Value time-weighted average of methanol (262 mg/m3) would result in a daily dose of about 1,500 mg, assuming an 8-hour inhaled volume of 10 m3 of air and absorption of 57%. 

TCDD was absorbed (less than 50% of the applied dose) at each interval of measurement, about 70% of detected radioactivity on the skin could be removed by swabbing with acetone. About 15% of the dose was detected in the liver of rats 24 hours after dermal exposure to 26 ng of 2,3,7,8-TCDD in 50% methanol (Poiger and Schlatter 1980). It was estimated that the amount absorbed from the dermal exposure represents 40% of the amount absorbed from an equivalent oral dose. Absorption of... 

The Matsuura method (57) compares the photolysis result of a solution actinometer with that of a thin crystalline film of equal surface area after exposure. Thus, evaporation of a solution containing the photoreactive substrate results in a thin crystalline film on the glass wall of a test tube, which is subsequently exposed to actinic radiation in a merry-go-round type photolysis apparatus. To test for complete absorption of the incident photons within the crystalline film, the evaporation process is carried out at various concentrations of the substrate, which leads to films of different thickness. If the yield of photoproduct after a certain exposure time is independent of the concentration of the original solution before evaporation, complete absorption of all actinic photons is established. The quantity of the photons absorbed by the crystalline film is then estimated by parallel photolysis of a 0.1 M solution of 2,4,6-triisopropylbenzophenone in methanol solution, which has a well-established quantum yield of 0 = 0.52 (58). The volume of this actinometer solution in the test tube is adjusted so that the crystalline film and the solution exhibit irradiated surfaces of identical size. In summary, this method provides approximate estimates of solid-state quantum yields however, differences in the reflection of the... 

II. Toxic dose. The fatal oral dose of methanol is estimated to be 30-240 mL (20-150 g). The minimum toxic dose is approximately 100 mg/kg. Elevated serum methanol levels have been reported after extensive dermal exposure and concentrated Inhalation. The ACGIH recommended workplace exposure limit (TLV-TWA) for inhalation is 200 ppm as an 8-hour time-weighted average, and the level considered immediately dangerous to life or health (IDLH) is 6000 ppm. 

Gas samples from room air were also detected with PTR-MS to estimate the indoor air quality [4,123]. Samples were taken from five rooms constructed more than 20 years ago. Two rooms had been equipped with new furniture and carpets only 2 months before the measurements were done. The concentrations of formaldehyde and ethanol were quite similar in the old and newly furnished rooms. Acetaldehyde, methanol, propanol, acetone, and toluene were strongly enhanced in the two newly furnished rooms. It was also found that the concentration of formaldehyde in four of the five rooms was higher than the maximum concentration allowed by Austrian law for permanent exposure dose to human [4]. 

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