Environmental factors, such as pesticides, have been linked in the past to an increased risk of autism and brain deterioration — they may even cause this risk. A new National Institutes of Health-backed study adds to this research; it focused on identifying fungicides that could potentially harm our brains. As you might have expected, the scientists from the UNC School of Medicine found a few culprits.

One particular class of commonly used fungicides changes gene expression in ways similar to that seen in patients with autism and brain degenerating conditions, such as Alzheimer's disease. Specifically, the fungicides pyraclostrobin, trifloxystrobin, famoxadone, and fenamidone stimulate free radical production and disrupt microtubules, a structure within neurons that’s involved in cell division.

The researchers said their work, which concentrates on genetics, offers a new approach to identifying chemicals that might harm us.

To begin their exploration, Dr. Mark Zylka, senior author and associate professor of cell biology and physiology, and his colleagues exposed mouse neurons to about 300 different chemicals. To find out whether any genes no longer functioned, the team sequenced RNA from these chemically-treated neurons and compared them to RNA from untreated neurons. This resulted in hundreds of data sets about gene information, so the researchers used computer programs to identify similarities in gene expression and then they followed the trail back to the test chemicals. Gene expression is the process of converting information stored in our DNA into instructions for making proteins (the workhorses inside our cells) and other molecules.

Zylka and his team narrowed their search down to six separate chemical classes, each of which contained chemicals that altered gene expression in the same way. “One of these groups of chemicals altered the levels of many of the same genes that are altered in the brains of people with autism or Alzheimer's disease,” Zylka said in a press release.

Chemicals in this group included the pesticides rotenone, pyridaben, and fenpyroximate, and a new class of fungicides that includes pyraclostrobin, trifloxystrobin, fenamidone, and famoxadone. The researchers emphasized that they can’t say these chemicals cause autism or Alzheimer’s, or harm the brain, because much more study is needed.

However, what Zylka and his colleagues discovered was these chemicals reduced the expression of genes involved in communication between neurons. Our brains cannot function normally when these genes fail to express properly. These chemicals also caused an elevated expression of genes associated with inflammation in the nervous system, or neuroinflammation — commonly seen in autism, Alzheimer’s, and other neurodegenerative conditions.

Additionally, these chemicals disrupted brain cell interior structures and stimulated the production of free radicals, particles damaging to cells and so implicated in a number of brain diseases. Again the scientist warn their results have not yet been tested in either animals or people, their research so far has been conducted only on in vitro cells.

The use of rotenone as an insecticide within the United States is currently being phased out. Pyraclostrobin is the active ingredient in products used by home gardeners. Trifloxystrobin is found in products used for grape crops. Fenamidone is active in products sold for use on potatoes and carrots. Famoxadone is the active ingredient in a product sold to farmers growing vegetables, potatoes, onions, and fruits. Pyridaben is commonly used on ornamental plants, flowers and foliage crops grown in greenhouses and outdoors. And fenpyroximate is an active ingredient in products for houseplants.

Source: Pearson BL, Simon JM, McCoy ES, Salazar G, Fragola G, Zylka MJ. Identification of chemicals that mimic transcriptional changes associated with autism, brain aging and neurodegeneration. Nature Communications. 2016.