MONOCROTOPHOS is a cheap pesticide used in agriculture, which helps plants look green and healthy. It is acutely toxic and has been linked to death of 23 school children in Bihar in 2013 and is recently blamed for the deaths of 14 devotees in a temple in Karnataka.
It is one of the oldest pesticides still in use, and although it is known to be toxic, it is not alone.
There are two kinds of toxic pesticides: acute ones which cause immediate effect, and chronic pesticides which have a built-up effect over a long period of time. Now governments usually move away from most of these acutely toxic ones because it creates immediate and visible problems. Monocrotophos is an highly acutely toxic. But somehow, it is still used for non-food products.
The World Health Organisation has placed monocrotophos in Class 1b — a category reserved for highly hazardous pesticides. The substance was banned in 2005 in India for use on vegetables.
Multiple routes of exposure
Monocrotophos can be absorbed into the human body through multiple pathways, including inhalation, skin contact and ingestion, and is acutely toxic by all routes of exposure. The first two modes of exposure put Indian farmers at an unusually high risk as farmers here mostly work without any protective equipment, and this puts them at risk of pesticide uptake by inhalation and absorption through the skin.
How does it affect the body
Monocrotophos is an organophosphate insecticide, which is a type of pesticide. These kinds of pesticides are known to be neurotoxins, which affect the work of neurons in the body. Monocrotophos is found to be lethal because of its action on the central nervous system of the human body. Here is a broad breakdown of the process with generous inputs from Kumar:
The nervous system is made up of a large and complex network of nerves. When a signal reaches the end of a nerve, it releases a substance called neurotransmitter that carries the signal to the adjacent nerves or organ. Many nerves in the nervous system release a neurotransmitter called acetylcholine. Once the signal passes onto the next nerve, an enzyme called acetylcholinesterase destroys the acetylcholine. And this is where monocrotophos comes in.
Organophosphorus compounds, like the pesticide at hand, block this enzyme, thus preventing the breakdown of acetylcholine. And hence, acetylcholine acts for an excessively long period of time, causing symptoms like twitches and increased secretions at the junctions between nerves. After a long duration of this process, muscles get fatigued leading to paralysis.
This also prevents communication in the nervous system, either between two nervous cells or between a nervous cell and a muscle cell. If this spreads throughout the body, death of the affected person becomes a highly likely outcome.
When inhaled, the first effects are usually respiratory. They may include a bloody or a runny nose, coughing, chest pain, short breaths and wheezing due to constriction or excess fluid in the bronchial tubes.
Skin contact with this pesticide may cause localised sweating and involuntary muscle contractions.
Eye contact will cause pain, bleeding, tears, pupil constriction and blurred vision.
Following exposure by any route, other systemic effects will either begin within a few minutes or may show up after up to 12 hours. These may include pallor, nausea, vomiting, diarrhoea, abdominal cramps, headache, dizziness, eye pain, blurred vision, constriction or dilation of the pupils, tears, salivation, and sweating.
Severe poisoning will affect the central nervous system, producing incoordination, slurred speech, loss of reflexes, weakness, fatigue, involuntary muscle contractions, twitching, tremors of the tongue or eyelids, and eventually paralysis of the body extremities and the respiratory muscles.
In severe cases, there may also be involuntary defecation or urination, psychosis, irregular heartbeat, unconsciousness, convulsions, and coma. Respiratory failure or cardiac arrest may even cause death.