Chlorpyrifos is an insecticide. Pure chlorpyrifos is made up on white or colourless crystals. It has a smell similar to sulphur—like rotten eggs. The insecticide was first registered on the market in 1965. [1,2]
Chlorpyrifos is an organophosphate insecticide, used on many different insects, including termites, ants, roundworms and mosquitoes. It works as a nerve inhibitor on the insects, effecting their cholinesterase (ChE) enzyme pathways. It was banned for home use in the US in 2006, however it is still found in insect baits. Currently, it is widely used across golf courses and farms for insect control. Products containing the insecticide are also used to treat wooden fences and utility poles.
Routes of Exposure 
People can be exposed to the insecticide by eating it, inhaling it, or getting it in their eyes or on their skin.
Pets or people can be exposed to chlorpyrifos if a bait station inside their home is broken.
Well water contamination could be a way of exposure. This would happen if the insecticide was used to control insects near the well, and it seeped into the water supply.
Symptoms of exposure can appear within minutes to hours of being exposed.
Chlorpyrifos poisoning affects a range of systems including the integumentary and respiratory systems.
Acute Effects 
Severity of symptoms depend on the level and type of exposure.
Chlorpyrifos exposure can result in a runny nose, increased saliva or drooling, and tears.
Acute exposure to the insecticide could result in headaches, nausea, dizziness and sweat.
Chronic Effects 
Chlorpyrifos is toxic to multiple body systems. Long-term exposure to the insecticide could result in vomiting, cramps, muscle weakness, twitching and tremors, and loss of co-ordination. It can also cause blurred or darkened vision, diarrhoea, unconsciousness, convulsions, loss of bladder and bowel control, difficulty breathing, and paralysis.
~h2First Aid Measures 
- Ingestion: DO NOT INDUCE VOMITING. Immediately contact a healthcare professional.
- Skin contact: Immediately wash affected area with plenty of water for at least 15 minutes. Remove contaminated clothing; do not re-wear until it has been thoroughly de-contaminated. Immediately contact a healthcare professional—but only after exposed skin has been thoroughly de-contaminated.
- Eye contact: Hold eyelids open, and rinse eyes for at least 15 minutes. Immediate medical attention is required.
- Inhaled: Take victim to the nearest fresh air source and monitor their breathing. If they are not breathing (and you are qualified), perform CPR with the aid of a pocket mask or one-way valve. Contact a medical professional immediately.
- General: Never administer anything by mouth to an unconscious, exposed person.
Exposure Controls/Personal Protection 
Engineering controls: Emergency eyewash fountains and safety showers should be accessible in the immediate area of the potential exposure. Ensure there is adequate ventilation. Whenever possible, material should be handled in a laboratory.
- Personal protection: Cotton overalls, a washable hat, elbow-length PVC gloves, and a face shield or googles. Wear resistant footwear, such as rubber or plastic boots. For specifications on PPE, check regulations in your jurisdiction.
The Occupational Safety and Health Administration (OSHA) has set an 8-hour time weighted average (TWA) concentration for chlorpyrifos of 0.2mg/m3.
Safe Work Australia has set an 8-hour time TWA for chlorpyrifos of 0/1mg/m3.