70% of the insecticides in current use in the United States are organophosphorous
(OP) pesticides, a total of around 90 million pounds per year. The OP
pesticides work by interfering with the nervous system of insects, a
mechanism that also affects the human nervous system when people are
exposed. Other health effects of individual OP pesticides vary; some
are highly acutely toxic, some cause development or reproductive harm,
and some are known or suspected endocrine disruptors.
A: As many of the first-generation organochlorine pesticides were banned in the 1970s, the agrochemical industry turned to the less persistent, but more acutely toxic organophosphate (OP) and carbamate compounds to control insect pests. Use of these pesticides increased rapidly, and by the late 1980s about 65% of insecticides applied nationwide were OPs and (closely related) carbamate compounds. Use has increased slightly since then to about 70% of total insecticide use.
These chemicals are applied to crops, buildings, ornamental plants and lawns. Agricultural uses include field applications on corn, cotton, canola, alfalfa, produce and nuts. Exterminators use OP pesticides in residential and commercial structures, and certain pest control products for cats and dogs contain organophosphorus compounds.
Products containing OPs include Dursban and Lorsban (containing the OP chlorpyrifos), Spectracide (containing the OP diazinon), and Sevin (containing the carbamate carbaryl). Residential uses of chlorpyrifos and diazinon were recently banned by the U.S. EPA.
A: Widespread exposure to the OP pesticides has recently been documented through research done by the U.S. Centers for Disease Control (CDC) and academic scientists*, which show that most people in the U.S. have breakdown products of these pesticides in their urine. Because OP pesticides generally do not persist in the environment for long periods of time and do not build up in the body fat of humans and other animals, the fact that these pesticides were found in such a high percentage of test subjects indicates that most people are routinely exposed to these chemicals on a daily basis.
People are commonly exposed to OP pesticides through eating fresh and processed vegetables, contacting pesticide-contaminated surfaces, breathing air near pesticide applications (both indoors and outdoors), and drinking pesticide-contaminated water. The multiple uses and ubiquitous nature of these chemicals result in routine exposures to many different OP pesticides for most people.
A: OPs are chemically similar to the chemical warfare agents originally produced during World War II, and they work by interfering with the nervous system of insects, as well as mammals, birds, and fish. Organophosphorus compounds block production of an enzyme called cholinesterase (ChE), which ensures that the chemical signal that causes a nerve impulse is halted at the appropriate time. Symptoms of 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.
OPs are among the most acutely toxic pesticides, with most of these chemicals classified by the U.S. Environmental Protection Agency as toxicity class I (highly toxic) or toxicity class II (moderately toxic). In addition, some OP pesticides cause developmental or reproductive harm, some are carcinogenic, and some are known or suspected endocrine disruptors. Detailed information on specific OP pesticides is available at http://www.pesticideinfo.org/. Sample chemical structures are available on Pesticide Action Network's pesticide tutorial page.
A: In response to the Food Quality Protection Act of 1996, the U.S. EPA began a process of re-registering pesticide active ingredients using a new set of standards that are more protective of public health than those used before 1996. One result is the requirement that combined exposure to pesticides with a common mechanism of toxicity (like the organophosphorus insecticides) be considered. Unfortunately, there is still no mechanism to evaluate the effects of the many simultaneous exposures to different groups of chemicals people experience every day.
The good news is that new restrictions have been imposed on most pesticides evaluated under the law. Some uses (such as residential uses of diazinon and chlorpyrifos) are being phased out altogether because of the unacceptable risks posed to children from their use. The bad news is that the process is slow, so many high-use chemicals have yet to be evaluated. And unfortunately the risks to agricultural workers are often simply overlooked. EPA has also not followed the letter of the law in its work, failing to fully assess the risks from all routes of exposure and failing to include additional safety factors for children that are required under the 1996 law.
Industrys attempts to delay enforcement of the law were successfully blocked by a lawsuit filed by the Natural Resources Defense Council, Pesticide Action Network, CalPIRG, Breast Cancer Fund, United Farm Workers, and Physicians for Social Responsibility. The settlement of the lawsuit in 2001 puts EPA on a strict timeline to finish the work for many high-use chemicals. The agency will be pressured to make some hard decisions in the next several years as the data come in. If the law is properly implemented, we may see significant new restrictions and reductions in OP pesticide use.
A: There are many things we can do to reduce the use of pesticides. We can use alternatives in our own homes, protecting our families from direct exposure. We can encourage the use of alternatives in agriculture by buying organic food and clothing. We can urge the agricultural industry and government officials to invest in research and promotion of alternatives, and let them know that we do not accept the use of toxic pesticides.
The following organizations are working on various aspects of eliminating OP pesticides and promoting alternatives. Visit their web sites and contact these organizations to learn what you can do to help.
Organizations Promoting Bans, Restrictions and Alternatives to Pesticides:
Organizations Documenting Pesticide Food Residues:
* See - C. Lu, D.E. Knutson, J. Fisker-Andersen, R.A. Fenske, "Biological Monitoring of Organophosphorus Pesticide Exposure among Pre-School Children in the Seattle Metropolitan Area," Environmental. Health Perspectives, 2001, Vol. 109, 299303; and C. Loewenherz, R.A. Fenske N. J. Simcox, and others. "Biological Monitoring of Organophosphorus Pesticide Exposure among Children of Agricultural Workers in Central Washington State," Environmental Health Perspectives, 1997, Vol. 105, 13441353.