Organophosphates (OP)

  • Specific groups of workers may be exposed to organophosphate fertilisers/ pesticides. For example, farmers and fruit growers can inadvertently be exposed to carbamate or organophosphate insecticides during crop spraying processes, and show symptoms of acute anticholinesterase poisoning e.g. headache, blurred vision, weakness, sweating and tremor. The mechanism of action is through the neurotoxic effect of inhibition of the neurotransmitter enzyme acetylcholinesterase.
  • Two longer term syndromes have been attributed to long term effects of organophosphate exposure, mainly in sheep dippers who have high and repeated contact with those agents. A plausible mechanism of action has not been found for the longer term or chronic effects attributed to organophosphate exposure. The long –term effects are not associated with cholinesterase depletion- the acute toxic mechanism- in any discernible or direct way. Little or no progress has been made in the elucidation of these potential long term effects in the last 10-20 years.
  • Screening for excessive exposure to anticholinesterases protects workers from harm and helps to identify unsatisfactory work practices. The exposure level which should trigger monitoring has not yet been adequately defined. Whole blood cholinesterase activity is the most widely used measurement for monitoring occupation exposure to OP and carbamates but is probably only practical in large companies employing stable work forces. It may not be practicable for small farms.

Health Surveillance

  • Health surveillance involves biological effect monitoring: cholinesterase in blood of workers exposed to certain organophosphorous pesticides is assessed.
  • Blood samples are best taken immediately after exposure but sampling towards the end of the day avoids the ‘diurnal variation’ effect. It is important that the blood tests should not be contaminated by exposure to anticholinesterases in the air or on the skin of the donor or sampler.Cholinesterases are unstable when kept at room temperature for long periods and samples should therefore be stored on ice or frozen prior to analysis.
  • Pre –employment assessment of relevant workers can be considered. This can assess the suitability of applicants to work with anticholinesterases. Pre-employment assessment may involve: an initial occupational history; a comprehensive medical history esp. re headaches, dizzy, vision problems; evaluation of alcohol consumption; physical examination; urinalysis; baseline cholinesterase determination (2 tests performed at least 3 days apart but not more than 14 days apart) and assessment of the ability to tolerate protective clothing and respirators.

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Other medical services we can provide

Isocyanates Medicals

This assessment will evaluate if someone is fit to work in certain environments.

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Skin Assessments

These checks will also identify if existing control measures in place are adequate

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Work Health Assessments

We will identify if an employee is fit to undertake night work

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