Chemicals are all around us, especially in our homes. While not all of them are harmful, many are untested, and scientists are striving to get a better idea of which ones can pose a threat we may not be aware of.

A recent study in Environmental Science & Technology looked at about 8,000 chemicals and came up with a new method to classify how often humans are exposed to them.

The Centers for Disease Control and Prevention keeps tabs on about 200 chemicals, and has issued recent reports on human exposure. Bisphenol A, or BPA, is one chemical that’s recently made headlines. BPA is used in everything from receipts to plastic, but now it’s under scrutiny because animal studies have shown BPA can impact hormone levels in developing fetuses.

The list of chemicals in the recent academic study was taken from a database of urine test results, meaning that the scientists worked backward based on what we already know for sure humans have in their bodies.


Identifying the levels at which humans are exposed to different chemicals is no easy task when you consider that the human body can transform a chemical into another chemical upon exposure. Plus, depending on their behavior, a person may be more or less exposed to specific chemicals than their peers.“It’s actually expensive and difficult to look for a specific chemical,” said John F. Wambaugh, Ph.D., a researcher at the Environmental Protection Agency’s National Center for Computational Toxicology. He conducted the new research with his colleagues.

“Our list is looking at about 8,000 chemicals and that’s more reflective of the backlog of untested chemicals that are out there in the environment,” he said.

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Which Chemicals Are We Most Exposed To?

Based on Wambaugh’s research, the top seven chemicals humans are most exposed to are:

Top 7 Chemicals Humans Are Exposed ToWhere Are These Chemicals Found?
1,2-Benzenedicarboxylic acid, di-C9-11-branched alkyl esters, C10-richA general purpose plasticizer used to make PVC flexible
Octadecanoic acidAlso known as stearic acid, it is commonly found in soaps, food additives, and cosmetics
Tannic acidCan be found in many foods and is also used to stain wood
FD&C Blue no. 1A colorant used to dye foods and other substances
Di(2-ethylhexyl) phthalate A chemical added to plastics to make them flexible, also known as DEHP
Hexanedioic acid Also known as adipic acid, it’s used in food, medicines, nylon, and plastics
Sodium dodecylbenzenesulfonateA colorless salt that is commonly found in detergents

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Legal Hurdles

Chlorowax 40, Cumene, and Diisononyl phthalate rounded out the study’s top 10 worst offenders for human exposure.

“The big issue is that we actually don’t know for sure how most of [these chemicals] are used … because there’s no law that requires a manufacturer to report that,” Wambaugh said.

In recent years, chemical manufacturers have been under pressure to be more transparent about their ingredients, and many companies have made it a point to be more open. For others, it’s a question of giving away their competitive advantage, which is why many are staying silent. Wambaugh said a lack of disclosure laws makes that possible.

“It’s like asking Coke, ‘What’s the secret ingredient?’” Wambaugh said.

Consider Indirect Exposure and Patterns of Use

Another obstacle to gauging human exposure to chemicals is that often we are only indirectly exposed.

Wambaugh said, for example, that many people think about what could be harmful in their shampoo, but fail to consider that the shampoo bottle could also expose them to potentially dangerous chemicals, including BPA.

However, “the majority of the chemicals don’t do much until you hit really, really high doses,” he said. That said, scientists don’t know the effects of being exposed to that same chemical over and over again in small doses if it’s found in multiple products.

In trying to find out how much of a chemical puts a person in danger, Wambaugh said human behavior comes into play. Someone who is around cleaners and plastic bottles daily, for example, may be exposed to certain chemicals more often than others.

He has used human tissue along with a robotic tester to try to measure at what dose a specific chemical becomes harmful.

The majority of the chemicals he has screened — about 2,000, via robot — do not do much harm, he said, “until you get to really, really high doses that are not at all realistic doses.”

“We don’t know enough to be afraid, but we should be afraid of what we don’t know,” Wambaugh concluded.

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