US EPA

58660 

Journal Article 

Plasma and red blood cell cholinesterase activity as indications of the threshold of incipient toxicity of ethyl-p-nitrophenyl thionobenzenephosphonate (EPN) and malathion in human beings 

Moeller, HC; Rider, JA 

1962 

1 

Toxicology and Applied Pharmacology
ISSN: 0041-008X
EISSN: 1096-0333 

4 

1 

123-130 

English 

14474998 

10.1016/0041-008X(62)90081-9 

BCI:BCI19624000023303 

The results of this investigation have established that 6 mg of EPN may be ingested daily for as long as 47 days without any significant effect on plasma or red blood cell cholines-terase activity. Sixteen milligrams of malathion may be ingested daily for as long as 47 days without any significant effect on plasma or red blood cell cholinesterase activity. The threshold of incipient toxicity appears to be 9 mg for EPN and 24 mg for malathion. Although when 6 mg of EPN and 16 mg of malathion were given in combination a significant depression of cholinesterase activity occurred, there did not appear to be any potentiation. This does not necessarily mean, however, that reaction to larger combined doses would be similar. It is of interest that with the daily administration of 9 mg of EPN and with the daily administration of 24 mg of malathion, a significant depression occurred; its maximum was not reached until approximately 3 weeks after administration of the drugs was discontinued. In view of these findings, it must be emphasized that prolonged studies are important in order to determine the threshold of incipient toxicity of anticholinesterase agents in human beings and to evaluate their effects at this level.