Pesticide Exposure Linked to Alzheimer’s Disease
By Robin Lally
Scientists have known for more than 40 years that the synthetic pesticide DDT is harmful to bird habitats and a threat to the environment.
Now researchers at Rutgers University say exposure to DDT—banned in the U.S. since 1972 but still used as a pesticide in other countries—may also increase the risk and severity of Alzheimer’s disease in some people, particularly those over the age of 60.
In a study published online Tuesday in JAMA Neurology, Rutgers scientists discuss their findings in which levels of DDE—the chemical compound left when DDT breaks down—were higher in the blood of late-onset Alzheimer’s disease patients compared to those without the disease.
DDT was used in the U.S. for insect control in crops and livestock and to combat insect-borne diseases like malaria. It was introduced as a pesticide during WWII. Rutgers scientists (the first to link a specific chemical compound to Alzheimer's disease) believe that research into how DDT and DDE may trigger neurodegenerative diseases, like Alzheimer's, is crucial.
“I think these results demonstrate that more attention should be focused on potential environmental contributors and their interaction with genetic susceptibility,” said Jason R. Richardson, associate professor in the Department of Environmental and Occupational Medicine at Robert Wood Johnson Medical School and a member of the Environmental and Occupational Health Sciences Institute. “Our data may help identify those that are at risk for Alzheimer’s disease and could potentially lead to earlier diagnosis and an improved outcome.”
Although the levels of DDT and DDE have decreased significantly in the U.S. over the last three decades, the toxic pesticide is still found in 75 to 80 percent of the blood samples collected from the Centers for Disease Control and Prevention for a national health and nutrition survey. This occurs, scientists say, because the chemical can take decades to breakdown in the environment. In addition, people may be exposed to the pesticide by consuming imported fruits, vegetables and grains where DDT is still being used or eating fish from contaminated waterways.
In the Rutgers study, conducted in coordination with Emory University Alzheimer’s Disease Research Center and the University of Texas Southwestern Medical School’s Alzheimer’s Disease Center, 74 out of the 86 Alzheimer’s patients involved (whose average age was 74) had DDE blood levels almost four times higher than the 79 people in the control group who did not have Alzheimer’s disease.
Patients with a version of ApoE gene (ApoE4), which greatly increases the risk of developing Alzheimer’s, and high blood levels of DDE exhibited even more severe cognitive impairment than the patients without the risk gene. Brain cell studies also found that DDT and DDE increased the amount of a protein associated with plaques believed to be a hallmark of Alzheimer's disease.
These sticky amyloid proteins—which may form in regions of the brain involved in memory, learning and thinking—break off and clump together in the brain and increase as the disease progresses. This new research is important, Richardson says, because it suggests that DDT and DDE may directly contribute to the process of plaque development.
“We need to conduct further research to determine whether this occurs and how the chemical compound interacts with the ApoE4 gene,” Richardson said.
Although the exact cause of Alzheimer’s disease, with which five million Americans are now suffering and millions more expected to fall prey with the graying of the Baby Boom Generation, is not known, scientists believe that late-onset Alzheimer’s may be linked to a combination of genetic, environmental and lifestyle factors. Much of the research into Alzheimer’s and other neurodegenerative diseases has mostly been centered on finding genetic connections, Richardson explained.
“This study demonstrates that there are additional contributors to Alzheimer’s disease that must be examined and that may help identify those at risk of developing Alzheimer’s,” Richardson said. “It is important because when it comes to diagnosing and treating this and other neurodegenerative diseases, the earlier someone is diagnosed, the more options there may be available.”
Scientists Ananya Roy, Stuart Shalat and Brian Buckley at the Environmental and Occupational Health Sciences Institute at Rutgers, Allan Levey and Maria Gearing at Emory University School of Medicine, and Dwight German at the University of Texas Southwestern Medical Center contributed to the research.
At first glance, you wouldn't think avocados and almonds could harm bees; but a closer look at how these popular crops are produced reveals their potentially detrimental effect on pollinators.
Migratory beekeeping involves trucking millions of bees across the U.S. to pollinate different crops, including avocados and almonds. Timothy Paule II / Pexels / CC0<p>According to <a href="https://www.fromthegrapevine.com/israeli-kitchen/beekeeping-how-to-keep-bees" target="_blank">From the Grapevine</a>, American avocados also fully depend on bees' pollination to produce fruit, so farmers have turned to migratory beekeeping as well to fill the void left by wild populations.</p><p>U.S. farmers have become reliant upon the practice, but migratory beekeeping has been called exploitative and harmful to bees. <a href="https://www.cnn.com/2019/05/10/health/avocado-almond-vegan-partner/index.html" target="_blank">CNN</a> reported that commercial beekeeping may injure or kill bees and that transporting them to pollinate crops appears to negatively affect their health and lifespan. Because the honeybees are forced to gather pollen and nectar from a single, monoculture crop — the one they've been brought in to pollinate — they are deprived of their normal diet, which is more diverse and nourishing as it's comprised of a variety of pollens and nectars, Scientific American reported.</p><p>Scientific American added how getting shuttled from crop to crop and field to field across the country boomerangs the bees between feast and famine, especially once the blooms they were brought in to fertilize end.</p><p>Plus, the artificial mass influx of bees guarantees spreading viruses, mites and fungi between the insects as they collide in midair and crawl over each other in their hives, Scientific American reported. According to CNN, some researchers argue that this explains why so many bees die each winter, and even why entire hives suddenly die off in a phenomenon called colony collapse disorder.</p>
Avocado and almond crops depend on bees for proper pollination. FRANK MERIÑO / Pexels / CC0<p>Salazar and other Columbian beekeepers described "scooping up piles of dead bees" year after year since the avocado and citrus booms began, according to Phys.org. Many have opted to salvage what partial colonies survive and move away from agricultural areas.</p><p>The future of pollinators and the crops they help create is uncertain. According to the United Nations, nearly half of insect pollinators, particularly bees and butterflies, risk global extinction, Phys.org reported. Their decline already has cascading consequences for the economy and beyond. Roughly 1.4 billion jobs and three-quarters of all crops around the world depend on bees and other pollinators for free fertilization services worth billions of dollars, Phys.org noted. Losing wild and native bees could <a href="https://www.ecowatch.com/wild-bees-crop-shortage-2646849232.html" target="_self">trigger food security issues</a>.</p><p>Salazar, the beekeeper, warned Phys.org, "The bee is a bioindicator. If bees are dying, what other insects beneficial to the environment... are dying?"</p>
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