Exposure

• You are unlikely to come into contact with malathion unless you live or work in or close to an area where it's in use. You can breathe it in while it's being sprayed or shortly thereafter; alternatively, you can absorb it through your skin by touching items covered in the spray. Agricultural workers and employees at factories where malathion is produced have the highest risk of exposure; people who spray it in their homes or gardens are also at some risk.
  
  

Persistence

• Once malathion enters the environment, sunlight, bacteria and water will typically break it down in the course of several weeks. Soil bacteria break it down rather rapidly, so it's very unlikely that significant quantities of malathion will enter groundwater supplies. In the air, the breakdown of malathion can lead to the formation of a more toxic compound called malaoxon. According to the Centers for Disease Control's Agency for Toxic Substances and Disease Registry, the amount of malathion remaining in fields or other areas a week after spraying should be very small.
  
  

Health Risks

• Malathion kills insects by interfering with the activity of enzymes called cholinesterases; these enzymes are vital for the proper function of the insect's nervous system. One possible concern about pesticides that work in this way would be their potential effects on mammalian nervous systems. Tests with lab animals have found that malathion has very low toxicity when ingested or inhaled by rats or when applied to their skin. At present, there is no conclusive evidence to show that malathion causes or would cause cancer in humans. Nonetheless, the National Institute for Occupational Safety and Health recommends that workers not be exposed to more than 10 milligrams per cubic meter of malathion for a 10-hour workday. Levels of 250 milligrams per cubic meter or above are very dangerous.
  
  

Precautions

• While malathion has low toxicity, it does have the potential to pose a human health risk, especially at higher concentrations. If you are an agricultural worker who comes in contact with this compound, it's important to ensure that you refrain from entering sprayed fields or areas for at least 6 days following application if you are hand-harvesting or hand-pruning and at least 12 hours following application in most other cases. You should also make sure you are wearing protective equipment. Families should avoid areas that have been recently sprayed for at least a week afterwards (longer for children who play near affected areas) and wear protective equipment if it has been applied in the garden or yard.