Each time you handle a pesticide, you are at some risk. The amount of risk depends on two things -the toxicity of that pesticide and your exposure to it. Risk = Toxicity x Exposure

Toxicity is a measure of how harmful or poisonous the pesticide is. There are 2 types of toxicity:

• Acute toxicity - the toxic response that results from a single exposure to the pesticide. The symbols and words on the front panel of a pesticide label give you information about the acute toxicity.
  
  Lethal Dose 50% (LD50) is a measure of Acute Toxicity. It is the dose (mg. of product per kg of body weight) that will kill 50% of the test animals within a stated period of time (24 hr.-7 days).
  
  
• Chronic toxicity - the toxic response that results from repeated exposures to small doses of a pesticide over a longer period of time. These toxic effects may not appear for months or years after exposure to the pesticide. The symbols on the label do NOT give information about the chronic toxicity of the product. Use protective clothing and equipment to help reduce exposure and the risk of chronic effects.

Cholinesterase Blood Tests

Organophosphorus and carbamate pesticides can affect your nervous system. These pesticides can change your serum and red blood cell levels of an enzyme called acetyl cholinesterase. The body uses this enzyme to transmit messages through the nervous system. If your cholinesterase levels fall, you can experience symptoms including trembling, twitching, blurred vision, difficulty breathing and heart difficulties.

People who use any of these pesticides on a routine basis should have regular cholinesterase blood tests. A family doctor can arrange these tests, which are covered by OHIP. Workers should have their test before beginning to handle these pesticides to show their baseline (normal) cholinesterase level. During the spray season, workers who spray organophosphorus or carbamate insecticides regularly for several weeks should have a cholinesterase blood test every 7-10 days. If a workers' cholinesterase level drops to below one-half their baseline level, they are showing signs of pesticide poisoning and must remove themselves from exposure to these pesticides until their cholinesterase level returns to normal.

Exposure is a measure of the contact workers have with the pesticide, which can occur in three ways.

• Dermal exposure occurs through the skin or eyes. The amount and rate of pesticide that may be absorbed depends on several things, including:
  • skin condition. If skin is moist, or has rashes, broken skin or scratches, the pesticide will be absorbed more easily
  • the part of the body exposed. Eyes, genital area, scalp and ear canals absorb pesticides at a higher rate than do hands or arms. Eyes absorb pesticides at a rate of 100%.
• Respiratory exposure (inhalation) occurs when small spray particles, dust, gases or vapors are inhaled.
• Oral exposure occurs when a pesticide enters the mouth or is swallowed.