(Beyond Pesticides, August 25, 2010) Exposure to pesticides while in the womb may increase the odds that a child will have attention deficit hyperactivity disorder (ADHD), according to researchers at the University of California-Berkeley School of Public Health. Maternal metabolites of organophosphate pesticides have previously been associated with neurobehavioral deficits in children. The California researchers are studying the impact of environmental exposures on the health of women and children who live in the Salinas Valley, an agricultural region with heavy pesticide use. They tested the urine of pregnant women for pesticide residue, and then tested the behavior of their children at ages 3 ½ and 5. The 5-year-olds who had been exposed to organophosphate pesticides while in the womb have more problems with attention and behavior than did children who were not exposed. Results are published online in the study entitled, “Organophosphate Pesticide Exposure and Attention in Young Mexican-American Children,” in the journal, Environmental Health and Perspectives. Previous studies have shown that exposure to some organophosphate compounds cause hyperactivity and cognitive deficits in animals. One study published in Pediatrics earlier this year found that exposure to organophosphates in developing children might have effects on neural systems and could contribute to […]

(Beyond Pesticides, July 27, 2010) Groups filed a lawsuit in federal court to force the Environmental Protection Agency (EPA) to decide whether or not it will cancel all remaining uses and tolerances for the pesticide chlorpyrifos, which has been banned for residential use, but continues to expose farmworkers and consumers through its use in agriculture. In September 2007, the Natural Resources Defense Council (NRDC) and Pesticide Action Network North America (PANNA) filed a petition with EPA asking the agency to ban chlorpyrifos. In the nearly three years since, the agency has not responded. NRDC and PANNA v. EPA, filed by the nonprofit environmental law firm Earthjustice on July 22, 2010, would force EPA to make a decision on the pesticide’s ban. “This dangerous pesticide has no place in our fields, near our children, or on our food,” said Earthjustice attorney Kevin Regan. “We’re asking a court to rule so that EPA will finish the job and ban this poison.” According to Beyond Pesticides, EPA’s 2000 negotiated settlement with Dow AgroSciences, which allows the highest volume chlorpyrifos uses to continue, represents a classic failure of the risk assessment process (including the so-called cumulative risk assessment which accounts for all chemicals with […]

(Beyond Pesticides, June 25, 2010) Two new studies published in the journal Environmental Science and Technology confirm that the majority of toxic contamination threatening national parks originates from agricultural pesticides and industrial operations. In one study an international group of scientists conducted research from 2003-2005 and detected elevated concentrations of various dangerous pesticides in all eight of the national parks and preserves. The other study collected samples of air, water, snow, sediment, lichens, conifer needles, and fish at remote alpine, subarctic, and arctic sites. Researchers found that these samples contained four current-use pesticides including dacthal (DCPA), chlorpyrifos, endosulfans, and y-hexachlorocyclohexane (HGH) as well as four historic-use pesticides including dieldrin, a-HCH, chlordanes, and hexachlorobenzene (HCB). Pesticide concentrations in snow are highest in Sequoia, Kings Canyon, Rocky Mountain and Glacier National Parks. Concentrations in vegetation are mostly dominated by endosulfan and dacthal, and are highest in Yosemite, Kings Canyon, Glacier, and Great Sand Dunes National Park and Preserve. Fish samples also show elevated concentrations of dieldrin and DDT (one of the first pesticides to be banned in 1972 because of Rachel Carson’s Silent Spring). Cold temperatures in alpine or arctic ecosystems tend to concentrate pesticides, which can also bioaccumulate in the local […]

(Beyond Pesticides, May 28, 2010) The repeated exposure to organophosphate and organochlorine insecticides can increase the risk of developing Alzheimer’s Disease (AD) or dementia later in life according to a new study published in the May issue of Neurology. The observational study entitled “Occupational exposure to pesticides increases the risk of incident AD” is one of very few studies to examine a link between pesticides and AD. Researchers lead by Kathleen M. Hayden, PhD of Duke University Medical Center examined residents 65 years and older from an agricultural community in Cache County Utah. Participants were assessed for cognitive ability at the inception of the study and again after 3, 7, and 10 years. Data showed that those repeatedly exposed to any pesticides were more likely to develop AD or dementia. Researchers found a higher incidence of AD among those exposed to organophosphates and organochlorines. The risk of AD associated with organophosphate exposure was slightly higher than the risk associated with organochlorines. Researchers also found an increase in dementia among those exposed to organophosphates or organochlorines; however this increase was not statistically significant. Dr. Hayden said that more research was necessary to determine a causal link. Organophosphates are known to reduce […]

(Beyond Pesticides, May 18, 2010) A team of scientists from the University of Montreal and Harvard University have discovered that exposure to organophosphate pesticides is associated with increased risk of Attention-Deficit Hyperactivity Disorder (ADHD) in children. Using data from the National Health and Nutrition Examination Survey, the study focused on 1,139 children from the general U.S. population and measured pesticide breakdown product levels in their urine. The authors conclude that exposure to organophosphate (OP) pesticides, at levels common among U.S. children, may contribute to a diagnosis of ADHD. “Previous studies have shown that exposure to some organophosphate compounds cause hyperactivity and cognitive deficits in animals,” says lead author Maryse F. Bouchard, a professor at the University of Montreal Department of Environmental and Occupational Health and scientist at the Sainte-Justine Hospital Research Center. “Our study found that exposure to organophosphates in developing children might have effects on neural systems and could contribute to ADHD behaviors, such as inattention, hyperactivity, and impulsivity.” Marc Weisskopf, PhD, ScD, another study author told Reuters, “What this paper specifically highlights is that this may be true even at low concentrations.” For children with a 10-fold increase in the concentration of the most common dialkyl phosphate metabolites […]

(Beyond Pesticides, March 30, 2010) Searching for clues to the mysterious disappearance of bees, known as “colony collapse disorder”(CCD), Penn State University researchers have identified widespread pesticide contamination of beehives. The study, “High Levels of Miticides and Agrochemicals in North American Apiaries: Implications for Honey Bee Health,” was published March 19, 2010 in the scientific journal Public Library of Science (PLOS). The study finds 121 different types of pesticides within 887 wax, pollen, bee and hive samples from 23 states. The top 10 most frequently detected pesticides are fluvalinate, coumaphos, chlorpyrifos, chlorothalonil, amitraz, pendamethalin, endosulfan, fenpropathrin, esfenvalerate and atrazine. Miticides are the most common contaminant in the wax and bees, and fungicides are the most common contaminant of pollen. For the full results of the study, including several tables of wax, pollen and bee sample data, download the study from the PLOS website. “The pollen is not in good shape,” Chris Mullin, PhD, lead author of the study, told Discovery News. The authors state that the 98 pesticides and metabolites detected in mixtures up to 214 parts per million (ppm) in bee pollen alone represents a remarkably high level for toxicants in the brood and adult food of this primary […]

(Beyond Pesticides, March 26, 2010) A new study by researchers at Columbia University’s Mailman School of Public Health has linked exposure to the insecticide chlorpyrifos to early childhood developmental delays. Chlorpyrifos is a broad spectrum organophosphate insecticide that was banned for household use in 2001, but is still widely used in agriculture. The study, entitled “Chlorpyrifos Exposure and Urban Residential Environment Characteristics as Determinants of Early Childhood Neurodevelopment,” was published online and will be published in print in the may issue of the American Journal of Public Health. The study examined 266 children born between 1998 and 2002 living in low income neighborhoods of the South Bronx and Northern Manhattan in New York City. Before being banned chlorpyrifos was widely used in these areas. Of the children studied, 47% were male, 59% were Dominican and 41% were African American. Researchers compared motor and mental development to levels of exposure to the pesticide at birth. They found that high concentrations of chlorpyrifos in umbilical cord blood (>6.17 pg/g) corresponds to a 6.5 point decrease in the Psychomotor Development Index, and a 3.3 point decrease in the Mental development index in 3 year olds. Previous research published in 2006 on the same […]

(Beyond Pesticides, February 17, 2010) In the largest study of its kind, researchers searched hundreds of Salinas Valley, California homes for pesticide compounds sticking to dust layers and discovered widespread residues of 22 residential and agricultural-use products. The study, “Pesticides in Dust from Homes in an Agricultural Area,” was conducted by an investigator from the California Department of Public Health and researchers with the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) with the University of California, Berkeley. CHAMACOS began recruiting pregnant women in the Salinas Valley for a long-term study of prenatal and infant chemical and allergen exposure in 1999. The center sampled study homes in 1999 and 2000 with a modified vacuum cleaner. The most common pesticides found were permethrin (467ppb) -a popular insecticide against home insect, and chlorpyrifos (74ppb). The U.S. Environmental Protection Agency (EPA) banned chlorpyrifos for home-use in 2000, but it is still used in agriculture. Other pesticides frequently detected include the herbicide dimethyl tetrachloroterephthalate (DCPA), methomyl, diazinon and a fungicide, iprodione. Household dust concentrations are significantly associated with nearby use of these chemicals on agricultural fields in the month or season prior to sample collection. The study reported that in […]

(Beyond Pesticides, January, 21, 2009) A new study concludes that exposures during pregnancy and childhood to insecticides that target the nervous system, such as organophosphates (OPs) and carbamates, are associated with childhood brain tumors. The researchers hypothesize that this susceptibility might be increased in children with genetic variations that affect the metabolism of these chemicals. The study, “Childhood Brain Tumors, Residential Insecticide Exposure, and Pesticide Metabolism Genes,” examines whether childhood brain tumors (CBT) are associated with the functional genetic variations. The study provides evidence that exposure to insecticides, paired with specific metabolism gene variants, may increase the risk of CBT. DNA was extracted from archival screening samples for 201 cases ≤ 10 years of age and born in California or Washington State between 1978 and 1990. Insecticide exposures during pregnancy and childhood were classified based on interviews with participants’ mothers. The children’s mothers reported whether they or anyone else had chemically treated the child’s home for insects including termites, fleas, ants, cockroaches, silverfish, or “other” pests. The results are consistent with the possibility that children with a reduced ability to metabolize organophosphate and carbamate insecticides might be at increased risk of CBT when sufficiently exposed. The researchers observed multiplicative interactions […]

(Beyond Pesticides, January 11, 2010) Yet another study has been published that further supports the causative link between pesticide exposure and Parkinson’s disease. The study, funded by the National Institute of Environmental Health Sciences (NIEHS), is published in the January issue of Epidemiology. The University of California, Los Angeles researchers looked at the association between Parkinson’s disease, organophosphate pesticides and the common gene variant, paraoxonase-1 gene Leu-Met 55 polymorphism (PON1-55 MM). The findings show that study participants with two copies of gene variant have a significantly increased risk of developing Parkinson’s disease when exposed to certain organophosphate pesticides used in agriculture. The population-based case-control study examined the DNA of 351 incident cases and 363 controls from three rural counties in California. The researchers then used pesticide usage reports and a geographic information system (GIS) approach to determine the study participants’ residential exposure to organophosphates. The PON1 gene codes for an enzyme that metabolizes organophosphate pesticides. Individuals with the variant MM PONI1-55 genotype that are exposed to organophosphates exhibit more than twice the risk of Parkinson’s disease compared to carriers of wildtype or heterozygous genotype and no exposure. In regards to exposure to diazinon, carriers of variant MM PONI-55 genotype show […]

(Beyond Pesticides, December 1, 2009) A new study published in the November 2009 issue of Occupational and Environmental Medicine, adds rhinitis, the inflammation of the mucous lining of the nose, to the long list of ailments linked to pesticide exposure. “Rhinitis associated with pesticide exposure among commercial pesticide applicators in the Agricultural Health Study,” examined data from 2,245 Iowa commercial pesticide applicators and evaluated the association between rhinitis and 34 pesticides used in the past year. Seventy-four percent of commercial pesticide applicators in the study reported at least one episode of rhinitis in the past year (current rhinitis), compared with about 20-30% of the general population. Pesticide exposure and rhinitis were assessed at enrollment using two self-administered questionnaires. The first, completed at enrollment, obtained detailed information on use of pesticides on the market at the time of enrolment as well as smoking history, current agricultural activity and demographics. The second questionnaire, sent one month later, more detailed information on the pesticides, as well as medical history, including rhinitis, conjunctivitis, sinusitis and asthma. Respondents reported using 16 herbicides, 11 insecticides, five fungicides and two fumigants in the past year. Five of the pesticides were significantly positively associated with current rhinitis: the […]

(Beyond Pesticides, November 17, 2009) According to a new study by researchers at the University of Wisconsin-Madison, exposure to low levels of the organophosphate insecticide chorpyrifos during pregnancy can impair learning, change brain function and alter thyroid levels of offspring into adulthood for tested mice, especially females. The study, “Long-term sex selective hormonal and behavior alterations in mice exposed to low doses of chlorpyrifos in utero,” was led by Beyond Pesticides board member and professor of zoology and environmental toxicology, Warren Porter, PhD. Read the full analysis of the study on the Rodale Institute website. On June 8, 2000, the Environmental Protection Agency (EPA) and Dow AgroSciences, reached an agreement to stop the sale of most home, lawn and garden uses for chlorpyrifos because of its health risks to children. However, its use continues in agriculture. According to advocates, this new study provides further evidence for the need to ban chlorpyrifos and fully protect farmworkers, their families, and rural communities from the toxic hazards of this outdated, unnecessary pesticide. According to the Rodale Institute, which provided part of the funding for the study, “The new animal study accentuates the risk of ultra-low levels of the common pesticide chlorpyrifos to cause […]

(Beyond Pesticides, November 3, 2009) Research by scientists at the University of Florida (UF) links Colony Collapse Disorder (CCD), the widespread disappearance of honey bees that has killed off more than a third of commercial honey bees in the U.S., to larval exposure to a cocktail of frequently used pesticides. Led by UF Institute of Food and Agricultural Sciences bee specialist Jamie Ellis, PhD, the researchers have finished a first round of testing on bee larvae exposed to the pesticides most commonly found in bee hives. The results were presented on October 22 at a meeting of the North American Pollinator Protection Campaign (NAPPC), which funded the study. The work gives insight into how the larvae react to these pesticides, which are usually only tested on adult bees, and sets the stage for the researchers to test the bees’ reaction to combinations of these pesticides. Just like mixing the wrong medications can have deadly and unpredictable results in humans, chemical mixtures pose a quandary for the bee industry. Bees are commonly exposed to multiple pesticides that are either applied to or nearby their hives. “Beeswax, honey and pollen can contain low mixtures of fungicides, insecticides, and herbicides. The larvae develop […]

(Beyond Pesticides, October 16, 2009) On October 14th, Earthjustice and Farmworker Justice filed a petition asking the U.S. Environmental Protection Agency (EPA) to set safety standards protecting children who grow up near farms from the harmful effects of pesticide drift. The groups are also asking the agency to adopt an immediate no-spray buffer zone around homes, schools, parks and daycare centers for the most dangerous and drift-prone pesticides, organophosphates. The petition was filed by the public interest law firms on behalf of farmworker groups: United Farm Workers, Oregon-based Pineros y Campesinos Unidos del Noreste, California Rural Legal Assistance Foundation, and the Farm Labor Organizing Committee, AFL-CIO as well as Physicians for social Responsibility, Washington-based Sea Mar Community Health Center, Pesticide Action Network North America, and MomsRising.org. Specifically, the petition states that the EPA has failed to address the facts that children are particularly vulnerable to pesticides according findings by the National Academy of Sciences (NAS) in 1993. Congress took recommendations from NAS and passed the Food Quality Protection Act in1996, requiring EPA to “ensure that there is a reasonable certainty that no harm will result to infants and children from aggregate exposure” to pesticides. However, while EPA has made some […]

(Beyond Pesticides, September 29, 2009) A new study reveals that children exposed to agricultural pesticides applied near their home have up to twice the risk of developing the most common form of childhood leukemia, according to the Northern California Cancer Center (NCCC). The study, “Residential proximity to agricultural pesticide applications and childhood acute lymphoblastic leukemia,” published in the October issue of Environmental Research, used a unique California database to reveal an elevated risk in acute lymphoblastic leukemia (ALL) among children living near applications of certain categories of pesticides used in agriculture. The study, led by Rudolph Rull, Ph.D., shows an elevated risk of ALL associated with moderate exposure, but not high exposure, to pesticides classified as organophosphates (odds ratio (OR) 1.6), chlorophenoxy herbicides (OR 2.0), and triazines (OR 1.9), and with agricultural pesticides used as insecticides (OR 1.5) or fumigants (OR 1.7). California is one of the few states in the country that requires active reporting of pesticide applications, including time, place, and the type and amount of pesticide used. For this study, researchers were able to link children’s entire residential histories from birth to the time of case diagnosis to this pesticide-use reporting database and identify agricultural pesticides that […]

(Beyond Pesticides, September, 15, 2009) On September 11, 2009, the Environmental Protection Agency (EPA) announced plans to place additional limitations on the use of three organophosphate pesticides ”” chlorpyrifos, diazinon and malathion ”” to protect endangered and threatened salmon and steelhead in California, Idaho, Oregon and Washington. The announcement comes in response to a series of lawsuits brought by Pacific Coast Federation of Fishermen’s Associations (PCFFA), the Northwest Coalition for Alternatives to Pesticides, and other salmon advocates, with legal representation from Earthjustice, aimed at removing toxic pesticides from salmon spawning streams throughout the northwest. In response to the litigation, the National Marine Fisheries Service (NMFS) in November of 2008 released a “biological opinion” that set forth a plan for protecting Pacific salmon and steelhead from three toxic organophosphate pesticides. That decision came after almost a decade of legal wrangling between salmon advocates led by Earthjustice and the federal government. The biological opinion prescribed measures necessary to keep these pesticides out of water and to protect salmon populations in Washington, Oregon, California, and Idaho. The announcement from EPA moves this work forward. Although the experts at NMFS recommended prohibiting aerial applications of the three pesticides within 1,000 feet of salmon waters […]

(Beyond Pesticides, August 7, 2009) A recent study published in the journal Environmental Health Perspectives has added to evidence that certain pesticides significantly increase one’s risk of developing Parkinson’s disease (PD). Researchers found that rural residents who drank private well water within 500 meters of fields sprayed with certain pesticides had an increased – up to 90 percent – risk of developing PD, and those with Parkinson’s “were more likely to have consumed private well water, and had consumed it on average 4.3 years longer.” The study evaluated more than 700 people, including carefully chosen controls, in Fresno, Kent, and Tulare counties. 17 percent reported drinking private well water between 1974 and 1999. Researchers focused on wells’ proximity to agricultural fields sprayed with pesticides, since private wells are not regulated, and many are shallow enough to be contaminated by pesticides seeping into groundwater. Researchers looked at 26 pesticides and six in particular, “selected for their potential to pollute groundwater or because they are of interest for PD, and to which at least 10% of our population were exposed.” Those are: diazinon, chlorpyrifos, propargite, paraquat, dimethoate, and methomyl. Propargite exposure was most closely correlated with incidence of PD, with a 90 […]

(Beyond Pesticides, July 23, 2009) A new study published in the August 2009 issue of Environmental Toxicology and Chemistry found that insecticides used in highly populated agricultural areas of California’s Central Valley affect amphibians that breed in the Sierra Nevada Mountains to the east. This study adds to the increasing evidence that pesticides impact areas and wildlife species that are miles from sources of pesticide application. Researchers from the Cooperative Wildlife Research Laboratory, Southern Illinois University and U.S. Geological Survey (USGS) examined the chronic toxicity of two of the insecticides most commonly used in the Central Valley- chlorpyrifos and endosulfan, to larval Pacific treefrogs (Pseudacris regilla) and foothill yellow-legged frogs (Rana boylii), the amphibians with declining populations that live and breed in meadows surrounding the Sierra Nevada. The results are discussed in “Toxicity of Two Insecticides to California, USA, Anurans and Its Relevance to Declining Amphibian Populations.” The study used laboratory testing to examine how the insecticides affected the two frogs at environmentally realistic concentrations. During testing, tadpoles were observed at various stages of development to see how the insecticides affected their growth and health. The researchers found that endosulfan was more toxic than chlorpyrifos to both species, and tadpoles […]

(Beyond Pesticides, July 6, 2009) Last week, the U.S. Environmental Protection Agency (EPA) proposed to formally evaluate the harmful effects of 74 pesticides on 11 endangered and threatened species in the San Francisco Bay Area over the next five years, and to impose interim restrictions on use of these pesticides in and adjacent to endangered species habitats. The proposal stems from a settlement agreement with the Center for Biological Diversity, which sued EPA in 2007 for violating the Endangered Species Act by registering and allowing the use of toxic pesticides in Bay Area endangered species habitats without determining whether the chemicals jeopardize those species’ existence. “Tens of millions of pounds of toxic and poisonous chemicals, known to be deadly to endangered species and harmful to human health, including proven carcinogens and endocrine disruptors, are applied in the Bay Area each year, and many of those find their way through runoff or drift into our soil, creeks and rivers, San Francisco Bay, and sensitive wildlife habitats,” said Jeff Miller, conservation advocate with the Center. “The toxic stew of pesticides in the Bay-Delta has played a major role in the collapse of native fish populations, and pesticides are a leading cause of […]

(Beyond Pesticides, June 25, 2009) Although it is known that infants are more susceptible than adults to the toxic effects of pesticides, this increased vulnerability may extend much longer into childhood than expected, according to a new study by researchers at the University of California, Berkeley. Among newborns, levels of paraoxonase 1 (PON1), an enzyme critical to the detoxification of organophosphate pesticides, average one-third or less than those of the babies’ mothers. It was thought that PON1 enzyme activity in children approached adult levels by age two, but instead, the UC Berkeley researchers found that the enzyme level remained low in some individuals through age seven. Based upon the findings, reported in the journal Environmental Health Perspectives, the study authors recommend that the U.S. Environmental Protection Agency (EPA) re-evaluate the current standards for acceptable levels of pesticide exposure. “Current EPA standards of exposure for some pesticides assume children are three to five times more susceptible than adults, and for other pesticides the standards assume no difference,” said Nina Holland, Ph.D., UC Berkeley adjunct professor of environmental health sciences and senior author of the paper. “Our study is the first to show quantitatively that young children may be more susceptible to […]

(Beyond Pesticides, June 17, 2009) A new study finds that toxic pesticides, including those already banned, persist in homes. The study’s results indicate that most floors in occupied homes in the U.S. have measurable levels of insecticides that serve as sources of exposure to home dwellers. These persistent residues continue to expose people, especially vulnerable children, to the health risks associated with these chemicals. Published in Environmental Science and Technology, the study, entitled “American Healthy Homes Survey: A National Study of Residential Pesticides Measured from Floor Wipes,” was conducted as a collaboration between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Housing and Urban Development. Five hundred randomly selected homes were sampled using alcohol wipes to collect dust from hard surface floors, mostly kitchen floor surfaces. The swipes were analyzed for 24 currently and previously use residential insecticides in the organochlorine, organophosphate, pyrethroid and phenylpyrazole classes, and the insecticide synergist piperonyl butoxide. Researchers found that currently used pyrethroid pesticides were, not surprisingly, at the highest levels with varied concentrations. Fipronil and permethrin, both currently used, were found in 40 percent and 89 percent of homes respectively. However, the researchers found that long discontinued pesticides like DDT and […]

(Beyond Pesticides, May 19, 2009) Nearly six months after federal scientists began issuing restrictions to protect salmon and steelhead in the Pacific Northwest and California, the U.S. Environmental Protection Agency (EPA) has yet to take even the first step toward implementing these protections. This delay follows almost a decade of legal wrangling in which a coalition of environmental and fishing groups, led by the non-profit public interest law firm Earthjustice, won a court order. Tell EPA to stop its foot-dragging and protect salmon and steelhead from toxic pesticides. The six pesticides that scientists have reviewed so far are some of the most dangerous chemicals used today. All six””chlorpyrifos, diazinon, malathion, carbaryl, carbofuran, and methomyl””are neurotoxic and pose serious risks to both humans and wildlife. While many of these pesticides have been phased out for residential use, they continue to expose wildlife and farmworkers through their use in agriculture. Thirty-one more chemicals will undergo review by scientists at the National Marine Fisheries Service (NMFS) in the next three years. The new restrictions require EPA to prohibit application of the six pesticides in or near salmon and steelhead habitat. They also require EPA to prohibit application when the weather may cause the […]

(Beyond Pesticides, March 5, 2009) A new study published in the March 2009 issue of Environmental Health Perspectives finds that pesticide combinations cause more harm to endangered salmon than ndividual pesticide exposure. This means that single-pesticide risk assessments required by the Environmental Protection Agency (EPA) inadequately assess hazards. Mixtures of organophosphate and carbamate pesticides are commonly detected in freshwater habitats that support threatened and endangered species of Pacific salmon. According to the researchers from the National Oceanic and Atmospheric Administration (NOAA) Fisheries and Washington State University, these pesticides inhibit the activity of acetylcholinesterase (AChE) and thus have potential to interfere with behaviors that may be essential for salmon survival. The researchers measured brain AChE inhibition in juvenile coho salmon exposed to sublethal concentrations of the organophosphates diazinon, malathion, and chlorpyrifos, as well as the carbamates carbaryl and carbofuran. The pesticides were tested individually and in combination. They plotted AChE levels on a curve to determine whether the toxicologic responses to binary mixtures were additive, antagonistic (lesser than additive) effect, or synergistic (greater than additive). The authors observed addition and synergism, with a greater degree of synergism at higher exposure concentrations. Several combinations of organophosphates were lethal at concentrations that were […]