[Relationship between exposure to chlorpyrifos and concentration of urinary alkylphosphates in termite control...

Chlorpyrifos (O, O-diethyl-3,5,6-trichloro-2-pyridinyl phosphorothioate; CP) has been used for insecticide to prevent infestation of termites. A study was made on occupational exposure to CP of termite control workers engaged in spraying this organophosphorus insecticide. Workers were engaged in two types of spraying; that is spraying CP under floor and spraying CP around house. All the under-floor sprayers wore respirators during spraying. CP levels in air near the breathing zone, contact amounts of CP with skin, and urinary alkylphosphates levels were higher in the under-floor sprayers than in the around-house sprayers. The personal ambient CP levels of the under-floor sprayers were 0.012 to 0.145 (8 h-TWA, mg/m3) lower than the threshold limit value (0.2 mg/m3) proposed by ACGIH. A maximum diethylphosphate (DEP) excretion was observed in the first urine collected the next day, while the highest diethylthiophosphate (DETP) was excreted in the last urine in the working day. In the excretion amount, DEP was higher than DETP. Amounts of CP collected in respirators used by the under-floor spraymen averaged 0.76 mg/respiratory comparable to their estimated theoretical value of 0.69 mg/m3. The urinary total alkylphosphate (DEP + DETP) level was more closely correlated with the contact amount of CP with skin (r = 0.86) than with the personal ambient CP level (r = 0.05). These results indicate that 1) respiratory absorption of CP was prevented by the use of respirator; 2) the urinary alkylphosphates were mainly derived from the dermal absorption of CP; and 3) biological monitoring using urinary alkylphosphates levels is an useful index for CP exposure.