Molecular Mechanisms of Acute Organophosphate Nephrotoxicity

Organophosphates (OPs) are toxic chemicals produced by an esterification process and some other routes. They are the main components of herbicides, pesticides, and insecticides and are also widely used in the production of plastics and solvents. Acute or chronic exposure to OPs can manifest in various levels of toxicity to humans, animals, plants, and insects. OPs containing insecticides were widely used in many countries during the 20th century, and some of them continue to be used today. In particular, 36 OPs have been registered in the USA, and all of them have the potential to cause acute and sub-acute toxicity. Renal damage and impairment of kidney function after exposure to OPs, accompanied by the development of clinical manifestations of poisoning back in the early 1990s of the last century, was considered a rare manifestation of their toxicity. However, since the beginning of the 21st century, nephrotoxicity of OPs as a manifestation of delayed toxicity is the subject of greater attention of researchers. In this article, we present a modern view on the molecular pathophysiological mechanisms of acute nephrotoxicity of organophosphate compounds.

Fifteen Years of Experience in Cholinesterase Monitoring of Insecticide Applicators

INTRODUCTION

Measuring cholinesterase(ChE) enzyme levels in red blood cells (RBC) and plasma has become a useful tool in the early detection of organophosphate and carbamate poisoning in insecticide handlers. Since 1974 the State of California has required testing of pesticide applicators to prevent disease. This study is a review of the testing experience of two physicians and using one laboratory so that a comparison can be made to previous studies by the author and others.

METHODS

The files of 366 workers who were referred by their employers for ChE activity monitoring were abstracted for patient data, employer identification, and testing data. Results were entered into the EPIINFO program for analysis.

RESULTS

A total of 366 workers from 45 companies were tested over a 15-year period between 1989 and 2004. Most were applicators. There were 690 attempts to establish baselines, of which 545 (79%) were successful. There were 519 monitoring tests on 228 workers, resulting in the removal from exposure of 18 employees, most in 1996. Self-reported exposure history and symptoms resulted in only 3 responses (.6%). The costs were significant ($47,160 total and $36 per test), especially when considering the failure of 145 (21%) employees to establish baselines. There was monthly and yearly variation in plasma and RBC baselines, monthly variance in plasma monitoring tests, and no monthly variance in RBC monitoring. The use of a third baseline test when the first two varied by 15% avoided two false positives. The mean time for recovery from ChE depression was 5.38 weeks.

DISCUSSION

The California ChE monitoring program remains a valuable tool. There was significant monthly and yearly variation in values for both baseline and monitoring plasma and RBC values, with the exception of RBC monthly variance. Self-reported symptoms were not found to be a valuable tool in measuring exposure. Rates of recovery from ChE depression were highly variable. The warning feature of the program was very effective. The costs of monitoring were substantial, but possibly not as great as a single workers' compensation case.

CONCLUSIONS

The California ChE monitoring program serves as a useful and cost-effective means of preventing organophosphate and carbamate overexposure. Elimination of the third baseline test requirement should be considered.