Does Genetics Or Environment Cause Diseases?

When examining why neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS), are increasing, it’s commonly assumed that age and genetics are the primary contributors to these diseases.

However, growing scientific evidence indicates that exposure to microplastics, air pollutants, pesticides, and other environmental toxins plays a significant role in common diseases like dementia and childhood developmental disorders.

It’s estimated that Americans are exposed to many of the 80,000 chemicals currently used in the United States, according to the New York Health Foundation. The large number of toxic chemicals makes it nearly impossible to determine each chemical’s effect on an individual.

However, researchers and neuroscientists are increasingly focusing on the exposome—the study of how environmental exposures affect human health and the role that individual genetics plays in it. The experts believe studying the exposome could help explain previously hidden causes of neurodegenerative diseases and developmental disorders.

“This is going to be one of the big frontiers to try to understand,” Dr. Walter J. Koroshetz, the former director of the National Institute of Neurological Disorders and Stroke, said. “The impact is gigantic. The ability to prevent neurologic diseases really rests on understanding what in the environment is driving them.”

Dr. Koroshetz was a co-moderator of the American Neurological Association’s (ANA) annual meeting in 2022, which focused on the links between toxic environmental exposure and neurological disorders. Neurology is a branch of medicine that specializes in disorders of the nervous system, including the brain, spinal cord, and sensory neural elements, such as the ears, eyes, and skin.

The brain, the body’s most complex and important organ, is likely the most sensitive to environmental toxins. However, researchers said it was hard to study the brain before the advances in technology. Due to these advances over the past two decades, investigators have taken a closer look at how environmental factors trigger Parkinson’s disease, a brain disorder that affects specific nerve cells.

“The world’s fastest-growing brain disease is largely man-made,” said Dr. E. Ray Dorsey, the David M. Levy Professor of Neurology at the University of Rochester Medical Center, and author of Ending Parkinson’s Disease.

According to Dr. Dorsey, who was also a speaker at the ANA’s annual meeting, “The world’s fastest-growing brain disease is largely man-made. The principal causes are toxic exposures to chemicals synthesized in the labs of chemical companies worldwide,” including certain pesticides like paraquat, components of air pollution, and substances like trichloroethylene (TCE). “Many of these likely causes of Parkinson’s disease are inhaled,” he said. “The nose may be the front door to the brain.”

Also at the ANA’s annual meeting, Deborah A. Cory-Slechta, a professor of Environmental Medicine at the University of Rochester Medical School, noted that there are more than 40,000 industrial chemicals currently in use in the United States. As a result, one person will often be exposed to many chemicals, such as farm workers applying pesticides or urban populations exposed to air pollution.

Researchers and environmental experts are calling for the U.S. Environmental Protection Agency (EPA) and other regulators to give more consideration to the scientific links between environmental toxins contributing to cancers and neurological disorders.

“Neurology is about 15 years behind cancer, so we need to sound the alarm on this and get more people doing research because the EPA is absolutely not protecting us,” said Frances Jensen, chair of the Department of Neurology at the University of Pennsylvania, who was the ANA president at the time of the symposium.

Marginalized Communities Are At Risk

The experts also point to studies that show marginalized groups, such as minorities, low-income individuals, and those with limited education, face the most exposure to environmental toxins due to unsafe housing and water, working in agricultural jobs, living near industrial plants and landfills, and other environmental hazards.

“I call this the exposome dis-equity,” Devon Payne-Sturges, an associate professor at the University of Maryland School of Public Health, said at the ANA’s 2022 symposium. According to Payne-Sturges, the EPA does not consider this enhanced toxicity, which is based on factors such as poverty.

“We really need to move towards understanding how these disproportionate exposures are happening in the first place and not just continue to describe these differences,” Payne-Sturges said. “We already know who is more likely to be exposed. We need to focus on the root causes.”

Cancer-Causing Substances Also in the Environment

Not only are researchers focusing on how environmental toxins cause neurological disorders, but they are also studying how exposure to toxic substances can cause cancer.

Studies have found that cancer results from changes in specific genes that affect the way cells function. Some of these genetic changes can happen naturally as DNA replicates when cells divide. The changes can also occur due to environmental exposure to substances, such as chemicals in tobacco smoke, or to forms of radiation, such as ultraviolet rays from the sun, according to Cancer.gov.

Some heavy metals, mineral oils, and naturally occurring gases are considered carcinogens—substances that can damage DNA and cause cancer. However, just because a substance has been labeled a carcinogen does not mean that it will cause cancer. A person’s cancer risk from carcinogens depends on many factors, including the amount and duration of exposure and genetic background.

In its 15th Report on Carcinogens, the National Toxicology Program has identified the following chemical substances as known human carcinogens:

• Wood Dust

Researchers say that some cancer-causing exposures, such as tobacco smoke and the sun’s rays, can be avoided, while others cannot, particularly when they are in the air we breathe, the water we drink, the food we eat, and the materials we use on our jobs.

Scientists are investigating environmental factors that may cause cancer to identify harmful exposures and their locations, since understanding them could help people avoid them.

Further Studies Warranted Between Toxins and Other Disorders

In addition to cancer, future studies could also include an investigation into why people who live in neighborhoods with elevated air pollution levels have a greater risk of stroke, and examine links between fetal exposure and neurodevelopmental disorders.

According to Rick Woychik, director of the National Institute of Environmental Health Sciences and the National Toxicology Program, it’s not just about pesticides since PFAS (a group of chemicals made by humans) are found everywhere in the environment, as are nanoplastics (extremely small pieces of plastic that come from the disposal or breakdown of larger plastic products). It’s knowing more about how toxins affect human health.

“And there are trillions of dollars’ worth of demand for nanomaterials, but it’s sobering how little we know about their toxicology,” Woychik said.

Source Link:
https://www.theguardian.com/us-news/2022/oct/23/environmental-toxins-neurological-disorders-parkinsons-alzheimers
https://nyhealthfoundation.org/resource/fact-sheet-potentially-toxic-chemicals-in-personal-care-products/a
https://medicalxpress.com/news/2022-10-symposium-highlights-emerging-toxicants-neurologic.html