Each pesticide generally belongs to a chemical family on which general health effects are known.
- Organophosphates: disturbs the peripheral nervous system (long acting)
- Carbamates: disturbs the peripheral nervous system (short acting)
- Organochlorines: disturbs the central nervous system (long acting)
- Pyrethroids: irritant to eyes, skin, and respiratory tract
- Thiocarbamates: irritant to eyes, skin, and respiratory tract
- Paraquat: irritant to skin and upper respiratory tract, if enters blood stream (through skin or ingestion) causes lung and kidney failure
Organophosphates
Organophosphates affect the central nervous system (brain) and peripheral nervous system (nerves found outside of the brain or spinal cord). Organophosphates attach themselves to the enzyme (acetylcholinesterase- AChE) that stops nerve transmission. Therefore, there is suppression of AChE and continuous electrical nerve transmission. This particularly affects the muscles, glands and smooth muscles that make the body organs function.
Farmers may have the following symptoms that can appear 30 minutes after exposure and may last up to 24 hours:
- General central nervous system:
- Fatigue
- Dizziness
- Headache
- Hand tremors
- Staggering gait
- Convulsions
- Loss of consciousness
- Coma
- From muscle over stimulation:
- Muscle weakness
- Muscle cramps
- Twitching eyelids
- From gland over stimulation:
- Salivary gland- excessive salivation
- Sweat gland- excessive sweating
- Lacrimal gland-excessive eye tearing
- From organ over-stimulation:
- Eyes
- Blurred vision (constricted pupils)
- Gastrointestinal
- Stomach cramps
- Nausea
- Vomiting
- Diarrhea
- Pulmonary (Lungs)
- Chest tightness
- Wheezing
- Cough
- Runny nose
Carbamates
Carbamates behave the same way as the organophosphates in that they suppress AChE, and cause over-stimulation of the nerves. The effect comes on sooner after exposure (as fast as 15 minutes) and does not last as long (3 hours).
Symptoms are the same with the exception of these symptoms below which are rare:
- Convulsions
- Loss of consciousness
- Coma
Organochlorines
Organochlorines affect the central nervous system. They are absorbed by fat so they can stay in the body a long time. As the fats cells in breast tissue can store organochlorines, it can measured in breast milk. The effects can occur within one hour after absorption and acute effects can last up to 48 hours. Some organochlorines (endosulfan) are rapidly and easily absorbed through the skin.
The nerves stimulating glands are not affected so you will not see:
- excessive salivation
- excessive sweating
- excessive eye tearing
- over-stimulation of small muscles like twitching eyelids
But you will see symptoms that are from disruption of central nervous:
- Muscle Weakness
- Dizziness
- Headache
- Numbness
- Nausea
- Loss of consciousness
- Convulsions
- Vomiting
- Hand tremors
- Staggering gait
- Anxiety/restlessness
- Confusion
Pyrethroids
Pyrethroids are irritants to the eyes, skin and respiratory tract. The symptoms last from 1-2 hours. The symptoms from spraying can be:
- Normal use:
- Numbness (hypersensitivity of skin)
- Shortness of breath (wheezing)
- Dry throat
- Sore Throat
- Burning nose
- Skin itching
- If ingested:
- Loss of consciousness/coma
- Convulsions
- High doses:
- Vomiting
- Diarrhea
- Excessive saliva
- Twitching eyelids
- Staggering gait
- Irritability
Thiocarbamates
Thiocarbamates are similar to the pyrethroids in that they also are irritants to the eyes, skin and respiratory tract. The symptoms can appear immediately when spraying and can be:
- Respiratory tract:
- Dry throat
- Sore Throat
- Burning nose
- Cough
- Eyes:
- Eye irritation (burning, itching)
- Red eyes
- Skin:
- Skin itching
- White spots on skin
- Scaling skin rash
- Red rash
Paraquat
Paraquat is very toxic to the skin and mucous membranes (inside of mouth, nose, eyes). Particles are too large to get deep into the lungs (manufacturer claims), but once paraquat is in the blood it collects in the lungs. If ingested (drink) it is very lethal. Symptoms can be:
- Skin:
- dryness, cracks
- erythema (redness)
- blistering
- ulcerations
- Nails:
- discoloration
- splitting nails
- loss of nails
- Respiratory tract:
- cough
- nosebleeds
- sore throat
- Eyes:
- conjunctivitis (irritation)
- ulceration, scarring, blindness
- Ingestion:
- lung fibrosis (stiff lungs)
- multi-system organ failure, specifically:
- respiratory failure
- kidney failure
Training manuals
The information on chemical families on this page is adapted from two training manuals by Helen Murphy on the health effects of pesticides. These manuals are available in English and in Thai language and can be downloaded from this website:
- Farmer and school children’s cross sectional survey on the health effects of pesticides
- A farmer self-surveillance system of pesticide poisoning
Download the manuals here:
farmer_kid_manual_thai (0.8 MB)
farmer_kid_manual_english (1.1 MB)
surveillance_manual_thai (0.6 MB)
surveillance_manual_english (0.6 MB)
In October-November 2002, Helen Murphy conducted training for two groups of farmers in Thailand to conduct cross-sectional surveys. More information on this training and the results of the surveys are on this website:
- Introduction
- Survey by vegetable growers Kanchanaburi
- Survey by mango growers Phitsanulok
- Conclusion
Links
- A good source of information on pesticides and symptoms of poisoning is the handbook “Recognition and Management of Pesticide Poisoning” by the U.S. Environmental Protection Agency. It can be downloaded from the EPA at https://www.epa.gov/pesticide-worker-safety/recognition-and-management-pesticide-poisonings
- More links with information on pesticides.