Similar to the chemical warfare agents produced during World War II, organophosphates (OPs) are some of the most common, and most toxic insecticides used today, adversely affecting the human nervous system even at low levels of exposure.
Organophosphates & Childhood Exposure
Organophosphates and Neurological Development in Children
Research shows a range of neurodevelopmental problems associated with prenatal and early childhood exposure:
- Impaired short term memory and mental development
- Increased reaction time & abnormal reflexes
- Mental & emotional problems (adolescent exposure)
Fruits and vegetables that are commonly eaten by children, including peaches, apples, grapes, green beans, and pears, are among the foods most commonly contaminated with organophosphates. (source: WhatsOnMyFood.org)
Developing youngsters are the most susceptible to OPs. Children can be exposed to OPs through the air, food, dust and soil, and even pets. Children of farmworkers and children in agricultural areas are among the most exposed to OPs, although urban children are also at risk.
Health Effects & Toxicity
Among the most acutely toxic pesticides, most organophosphates are classified by the U.S. Environmental Protection Agency as highly or moderately toxic. They interfere with the nervous system by inhibiting an enzyme called acetylcholinesterase. Under normal conditions, acetylcholinesterase controls nerve impulses--sending chemical signals to halt the nerve impulse at the appropriate time. When organophosphates impede this process, the nervous system becomes severely overstimulated, resulting in immediate neurological dysfunction.
Symptoms of acute exposure include nausea, headaches, twitching, trembling, excessive salivation and tearing, inability to breathe because of paralysis of the diaphragm, convulsions, and at higher doses, death.
Longer term, lower dose exposure to organophosphate pesticides is linked to a number of health problems:
- Developmental Effects: Organophosphates interfere with healthy neurodevelopment, leading to behavioral problems and lower cognitive function. Children exposed to OPs are more likely to meet the diagnostic criteria for ADHD, a recent study shows.
Reproductive Effects: As endocrine disrupters, organophosphates have a significant impact on the human reproductive system. The presence of OP metabolites in the body is associated with reduced levels of testosterone and other sex hormones. Exposure to OPs may have an adverse effect on male fertility.
- Cancer: Although most OPs are not considered carcinogenic, the CDC reports that several studies link organophosphate exposure to leukemia and lymphoma. The U.S. EPA also classifies the OP diclorvos as a "probable human carcinogen."
- Parkinson's Disease: Since OPs affect the brain, it's not surprising that they have been linked to neurological disorders. Living near applications of diazinon, chlorpyrifos, dimethoate has been found to increase the risk of Parkinson's Disease.
- Prenatal and Childhood Exposure to Pesticides and Neurobehavioral Development: Review of Epidemiological Studies
- Attention-Deficit/Hyperactivity Disorder and Urinary Metabolites of Organophosphate Pesticides
Since the advent of chemical warfare during World War II, organophosphorous compounds have become widely available as pest-control agents. Because of their relatively low cost and ability to be applied on a wide range of target insects and crops, OPs have become the most widely used class of insecticides in the United States. Organophosphates are also among the most common active ingredients in pesticides poisonings.
OPs of primary concern include: azinphos-methyl, chlorpyrifos, diazinon, dichlorvos, dimethoate, ethephon, malathion, methamidophos, naled, and oxydemeton-methyl. Detailed information on specific OP pesticides is available in Pesticide Action Network’s internet database.
- In a 2006 study conducted by the small California rural community of Lindsay, 12 participants documented the presence of chlorpyrifos in their bodies. Seven of the eight participating women were above the EPA established “acceptable” limit for pregnant and nursing women.
- Yakima Valley, Washington Air Monitoring Results (2006) Monitoring results revealed detectable levels of chlorpyrifos in the homes of Yakima Valley residents.
Environmental Impacts of OPs
Many metabolites (or breakdown products) of organophosphates are more toxic than the primary chemicals themselves--making them acutely lethal to sensitive species like amphibians, says a 2007 USGS study:
- Major metabolites of chlorpyrifos and malathion were 100 times more toxic than their parent compounds to frogs in California’s Central Valley, where nearly 25% of the nation’s organophosphate use is concentrated.
Because organophosphates share a common toxicity mechanism, exposure to several OP insecticides and their breakdown products could intensify their toxic effects. Heavy organophosphate use in California is thought to contribute to the decline of several local frog species. The National Marine Fisheries Service concluded that the use OPs threatens endangered salmon species in the Pacific Northwest.
Some organophosphates travel long distances and persist in cold climates. Researchers have detected OPs in Arctic and sub-Arctic environments:
- Ice core samples from Svalbard, Norway, revealed 5 OP compounds: chlorpyrifos, terbufos, diazinon, methyl parathion, and fenitrothion. (Current-Use and Legacy Pesticide History in the Austfonna Ice Cap, Svalbard, Norway)
- The Arctic Monitoring and Assessment Program 2009 Arctic Pollution reports the presence of chlorpyrifos in a number of locations: Surface water, ice, & fog from the Bering & Chukchi seas; Alaskan snow and fish from Alaskan parks; and Arctic & Subarctic Canadian lakes
A number of less-toxic alternatives to organophosphate pesticides are currently available and in use around the country and around the world. The University of California produced a special report on the use of OP alternatives in California. These alternatives include:
- Pheromones: chemicals secreted by insects for communication--to disrupt insect mating
- Cultural controls: crop rotations, manipulating planting dates, reducing of pest habitats and improving crop vigor
- Less toxic, more pest-specific alternative insecticides
Research & Factsheets
- Centers for Disease Control and Prevention Frequently Asked Questions about Organophosphates
- Extension Toxicology Network Toxicology Information Brief on Cholinesterase Inhibition
PAN Pesticide Info Database: Organophosphates
- CDC Fourth National Report on Human Exposure to Environmental Chemicals. The report reviews research on human exposure and health effects of organophosphates and presents its biomonitoring data on organophosphates in humans.
- U.S. EPA Revised Cumulative Risk Assessment for Organophosphates. This is a technical document that discusses cumulative risk from exposre through food, drinking water & residential uses.
Scientific Journal Articles on OPs and Human Health
- Acute Pesticide Poisoning Among Agricultural Workers in the United States, 1998–2005. Provides poisoning data for organophosphates.
- Chemical Trespass: Pesticides in our bodies and corporate accountability. PAN's 2004 analysis discusses CDC data and examines human exposure to & body burden of organophosphates. (Spanish Version)
- Fields of Poison 2002: California Farmworkers and Pesticides. The Californians for Pesticide Reform analysis details incidents of OP poisonings in California. (Spanish Version)
Second-Hand Pesticides: Airborne Pesticide Drift in California