Issue: Clinical Evaluations as a Component of Response

What should be the appropriate triggers for clinical evaluation of persons potentially exposed to methyl parathion?

  1. Symptomatic illness suspected to be related to methyl parathion may often include patients with only nonspecific symptoms. This pattern is expected to be predominant with chronic/subacute exposures. Testing does not necessarily have to be performed systematically by the agency. The agency may decide to target high-risk groups only. Information should be provided to others who want testing to take to their own providers.
  2. In certain cases, individuals with confirmed exposure based on environmental testing may request clinical evaluation even if asymptomatic. Such individuals should be dealt with on a case-by-case basis. For example: Inhabitants of a home that has been treated with methyl parathion at levels that require minimal intervention are asymptomatic. However, another resident of that home may be symptomatic and has tested positive for significant exposure. The asymptomatic individual may request evaluation.
  3. High-risk individuals identified by urine monitoring or environmental monitoring criteria: Group I should also be clinically evaluated. Agencies should consider systematically screening those evacuated from their homes. Logistics of this screening may depend on local resources. A self-administered questionnaire could be used.

Should an individual’s health status be used as a criterion for response either independently or in conjunction with environmental or urine monitoring results?

Only if the person meets well-defined clinical criteria for poisoning: markedly depressed cholinesterase levels. For screening purposes, a cholinesterase level would be considered markedly depressed if it falls below the laboratory reference range. Because MP appears to somewhat preferentially inhibit RBC cholinesterase, this decision should be based primarily on the RBC enzyme. Plasma cholinesterase is depressed below the reference range in up to 3% of the U.S. population who are heterozygous for a genetic variant of that enzyme. In cases where screening tests are ambiguous, follow-up testing should be done. Special consideration should be given to individuals in high-risk groups.

What measure should be taken to increase the environmental medicine capability of the local health care establishment to respond appropriately and to recognize the adverse health consequences of methyl parathion exposure?

Preferably, arrangements should be made with regional occupational health specialists, for example, the Association of Occupational and Environmental Clinics (AOEC).

Direction and support can also be given to patients and medical providers through telephone support from the regional poison control centers and the National Pesticide Telecommunication Network; poison centers have the advantage of being available around the clock 7 days a week. The disadvantage of this recommendation is that it might require funding and would represent an additional agency requiring information on details of clean-up procedures and protocols. Liaisons with national or state organizations (i.e., the American Academy of Family Physicians), and arrangements to include such groups on the agenda of state or national meetings would also be useful.

Information to local providers as a secondary alternative:

  • on-site by recognized experts in organophosphate exposure (i.e., grand rounds, local medical society meetings)
  • videoconferencing
  • availability of recognized experts by telephone contact, if needed at the discretion of the health care provider, on a case-by-case basis
  • continuing medical education presentations, written material (such as ATSDR’s OP case study); audiocassettes; web pages; medical society meetings; journal newsletters of local medical society; medical licensing board newsletters
Page last reviewed: June 20, 2014