Propoxur

IUPAC name 2-isopropoxyphenyl methylcarbamate Molecular formula C11H15NO3 Toxicity class USEPA II WHO II 

Toxicity Propoxur is highly toxic via the oral route. The acute oral LD50 is 50 mg/kg in rats and mice and 40 mg/kg for guinea pigs. Propoxur is only slightly toxic via the dermal route, with acute dermal LD50 of more than 5,000 mg/kg in rats. The acute LC50 for rats (4 hours) is more than 0.5 mg/L. Studies have shown that propoxur does not cause skin or eye irritation in rabbits. 

Like other carbamates, propoxur can inhibit the action of cholinesterase and disrupt nervous system function. Depending on the severity of exposure, this effect may be short-term and reversible. 

Human adults have ingested single doses of 50 mg of propoxur without apparent symptoms. Prolonged or repeated exposure to propoxur may cause symptoms similar to acute effects. Propoxur is very efficiently detoxified (transformed into less toxic or practically nontoxic forms), making it possible for rats to tolerate long periods of daily doses approximately equal to the LD50 of the insecticide, provided that the dose is spread out over the entire day, rather than ingested all 

Synonyms 3-tolyl A-methylcarbamate 3-ethylphenyl A-methylcarbamate m-cresyl methylcarbamate A-methylcarbamic acid m-cresyl ester methylcarbamic acid 3-tolyl ester Tsumacide 

Colorless crystalline solid no odor melts at 76°C (168.8°F) sparingly soluble in water 

Highly toxic by ingestion and moderately toxic by inhalation and skin absorption cholinesterase inhibitor exhibits acute, delayed, and chronic toxicity toxic effects are those of organophosphorus pesticides and carbamate esters the symptoms include excessive salivation, lacrimation, blurred vision, headache, labored breathing, twitches of muscle, loss of reflexes, headache, weakness, sweating, nausea, giddiness, vomiting, cramps, diarrhea, convulsions, and coma U.S. EPA-listed extremely hazardous substance. 

LD50 oral (rat) 268 mg/kg LD50 skin (rat) 268 mg/kg LD50 inhalation (rat) 128 mg/m hour 

Synonyms o-isopropoxyphenyl A-methyl-carbamate Al-methyl-2-isopropoxyphe-nylcarbamate o-isopropoxy phenol methylcarbamate methylcarbamic acid o-isopropoxyphenyl ester Aprocarb Bay-gon Isocarb Sendran 

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Propane suttone beta-Propiolactone Propionaldahyde Propoxur ... 

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Propoxur n-Pjopyl acetate n-Propyl alcohol Propylene... 

In addition, the use of biological monitoring has the advantage that skin penetration under particular conditions of protective clothing is included as well in the approach. The results of a dose-excretion study of propoxur by Meuling et al. (1991) using volunteers indicate a significant increase of the dermal uptake of the compound under conditions of occlusion, where there is increased blood flow, skin temperature, and skin moisture. 

In this part of the study, the internal dose of propoxur was assessed for HV applicators (n = 9) and harvesters (n = 18) using biological monitoring in two trials. In the first trial, workers wore their normal work clothing, followed by a trial where the same workers wore additional protective clothing. The minimum period between the two trials was 5 days. 

The test substance Undeen (active ingredient propoxur, 200 g/L) was applied by hand-held, high-volume spraying equipment at an application rate of a minimum 25 g active ingredient (a.i.) per 1000 m2 and a volume rate of approximately 100 L/1000 m2. 

The internal dose of propoxur was measured by assessing the total amount of 2-isopropoxyphenol (IPP) excreted in the urine, collected over a period of 24 hr from the start of exposure, and described in detail in previous studies (Brouwer et al., 1993 Meuling et al., 1991). Volunteer kinetics studies revealed a one-to-one relationship of absorbed propoxur and excreted IPP on a mole basis. Based on the results by Machemer et al. (1982), a pulmonary retention of 40% was used to calculate the relative contribution of the respiratory exposure to the internal exposure. To estimate the contribution of the dermal exposure, the calculated respiratory portion was subtracted from the total amount of IPP excreted in urine. 

Figure 1 Distribution of the potential dermal exposure of applicators (N = 3, n = 9) to propoxur and of harvesters (N = 6, n = 18).

Table 2 Ranges (and Medians) of Actual Exposure of the Hands (in pg Propoxur)...

Concentrations of propoxur in the breathing zone ranged from 0.6 to 25 (median, 0.7) pg/m3, and from 0.4 to 29.4 (median, 1.2) pg/m3 for applicators in exposure scenarios without and with protective clothing, respectively. For... 

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