Endocrine disruptors are chemicals that mess with the body's normal functioning.

T hey can contribute to lowered IQs, raised infertility rates, obesity, and low birth weights, among other things.

Leo Trasande, a pediatrician who studies the effects of these chemicals on people, warns of their effects in his new book, "Sicker, Fatter, Poorer."

Trasande says that with a few simple hacks, we can make our lives a little safer by avoiding these chemicals when possible.

The endocrine-disrupting chemicals he's most worried about are in our carpets, clothes, canned and packaged foods, cosmetics, and even receipts.

Through the course of a single day, your hands, mouth, and body come in contact with countless pieces of paper, plastic, fabric, and furniture.

You probably don't think about the chemicals these substances might harbor, or consider that they have a drug-like effect on health. But some do. They can make metabolisms slow down, subtly lower IQs, contribute to ADHD in children, and mess with sperm counts in men.

They’re called "endocrine disruptors," and they're around us all the time. The chemicals change how our bodies work by shifting the way hormones operate, according to Leo Trasande, a pediatrician and public-health researcher at NYU Langone Health.

"Hormones are the basic signaling molecules in our body that take on so many actions for practically every organ system," Trasande told Business Insider. "And endocrine disruptors are synthetic chemicals that scramble those signals, contributing to disease and disability."

Jessica Alba, Marla Weston, and Leo Trasande join the Safer Chemicals, Healthy Families Coalition on Capitol Hill to discuss the Safe Chemicals Act in 2011. Riccardo S. Savi/FilmMagic

In his new book, "Sicker, Fatter, Poorer: The Urgent Threat of Hormone-Disrupting Chemicals to Our Health and Future ... and What We Can Do About It," Trasande lays out the four big categories of endocrine disruptors he’s most concerned about, based on evidence from scientific studies and observations in his patients.

They are:

Bisphenols, like BPA, which are often found in the linings of aluminum-canned food and drinks and on cash-register receipts.

like BPA, which are often found in the linings of aluminum-canned food and drinks and on cash-register receipts. Brominated flame retardants that are in some carpets, furniture, and clothing.

that are in some carpets, furniture, and clothing. Synthetic pesticides on food.

on food. "Plasticizer chemicals" called phthalates that show up in plastic food packaging, lotions, and cosmetics.

BPA makes fat cells bigger, contributing to obesity and lower sperm counts

The chemical BPA, and others like it, could make the body turn more calories into fat instead of muscle, predisposing people to obesity.

In the lab, BPA acts like an obesogen. "It makes fat cells bigger," as Trasande writes. This is especially true if human embryos are exposed to the chemicals while still in a mother's womb.

Trasande said the obesogen effects of BPA are fairly small compared to what diet and exercise can do for health, but they're real.

"BPA exposure may explain nearly 2% of all obesity in 4-year-olds," Trasande says in his book. That stat is based on his analyses of data on childhood obesity and adult heart issues published in the journal Health Affairs in 2014.

The chemical is also dangerous for babies and pregnant women; it can up the odds of a premature birth, and mess with placenta function.

Bisphenols like BPA are chemicals that are used in manufacturing of both plastics and resins. We come into contact with them on thermal receipt paper, linings for canned food, some dental sealants, and plastic containers. Jimmy Kimmel Live

Men are not immune to the effects of BPA, either. The chemical can mess with androgens (male sex hormones) like testosterone, contributing to lower sperm counts, and even testicular-cancer rates.

The vast majority of us are exposed to the chemical. A 2013-14 CDC survey suggested 95% of US adults have detectable levels of BPA.

Counter to the adage that "the dose makes the poison," with hormone-disrupting chemicals there are often nonlinear relationships between the amount of chemical exposure and risk as the body's enzymes duke it out and compete with the hormone disruptors.

"The notion that everything needs to be linear — in a straight-line relationship — is really our own intellectual construct on a scientific reality that's much more complicated," Trasande says.

Many manufacturers are switching to BPA-free products. But that doesn't always mean they're safer, Trasande says, because many of the so-called replacements are just BPA relatives and the chemicals have similar effects on our health.

"To a large extent, when you don't know what's replacing [BPA], it's often BPS, BPF, BPP, BPZ — what I like to joke of as the artist formerly known as Prince," he said.

Furniture foam often has firefighting chemicals in it. But they don't work very well, and they can change how our bodies process fat. Shutterstock

Brominated flame retardants found in most furniture we use

Brominated flame retardants — flame-stomping chemicals found in furniture, carpeting, clothing, and car-seat foam — can change the way the thyroid functions in a similar way to BPA, shifting how the body processes fats and carbohydrates.

What's more, a 2012 Chicago Tribune investigation found that the firefighting chemicals, which are standard fare in foam cushions, don't work well to stop flames.

One large study of the flame retardants in houses pinpointed a link between ADHD and exposure to the chemicals. More research is ongoing.

Concentrations of the chemicals in human blood, sweat, and breast milk are much higher in the US than in parts of the world, such as Europe, where more brominated flame retardants are banned.

John Weiss looks over his damaged crop on his farm in Dell Thomson Reuters

Chemicals we spray to kill bugs can mess with us too

Certain pesticides used on food are also a concern, including bug-killing chlorpyrifos pesticides. These have been shown to impede brain development, making changes to the way a woman’s thyroid functions during pregnancy.

In the 1970s and '80s, before the chemical was banned in homes, doctors started noticing an increase in tinier and shorter premature babies being born, even in homes with low levels of the chemicals. After the Environmental Protection Agency banned the use of chlorpyrifos in homes, in 2000, birth weights went back up.

Exposure to chlorpyrifos can have lasting effects on child development. One 2015 study in kids between the ages of 11 and 14 found prenatal exposure to the chemical was linked to more arm tremors, which are also common in adults who've been exposed to lead. The chemicals are still used in agriculture.

Flexible plastics can also contribute to cancer

Finally, Trasande is concerned about phthalates, chemicals that help make plastics more flexible and durable. They appear in raincoats, flooring, hair spray, nail polish, plastic food packaging, and toys.

According to the US government, "one phthalate, Di (2-ethylhexyl) phthalate (DEHP), is an endocrine disruptor and can cause cancer." Additionally, the government says some phthalates can mess with normal reproduction and child-development processes.

In some studies, women tended to have more of the chemicals in their bodies than men because of beauty products they use. But anyone who eats packaged food or breathes in household dust probably has phthalates in their system.

More research on what these chemicals are doing to us is needed, but we do already have some evidence that they're leading to premature births, which can set kids up for a whole host of health problems later in life, including vision and hearing issues, chronic diseases like diabetes, anxiety, depression, and learning disabilities.

The plasticizing chemicals may also be linked to decreases in male testosterone levels. Scientists need to know more about the plastics before they'll say that conclusively, though.

Read more: Dangerous 'forever chemicals' have been found in US drinking water at alarmingly high rates — here's what to know about PFAS

Recently, manufacturers, retailers, and state lawmakers have started to pay more serious attention to the dangers of hormone disruptors, and they're making some changes.

Since 2013, California no longer requires furniture to contain flame retardants (a previous requirement for 38 years).

What you can do to reduce your exposure

Eat less canned food and more fresh produce. Trasande is a fan of organic farming because it generally excludes synthetic pesticides, but studies suggest that eating whatever fresh produce you can afford is the best strategy for your health.

Say no to paper receipts. This can help receipt-handling cashiers, who often have elevated levels of BPA in their urine.

Don't microwave plastic containers or put them in a dishwasher as the heat promotes chemical leaching. Throw kitchen plastics away when they become etched or scratched.

Avoid the recycling Nos. 3, 6, and 7, which are common plastics found in shampoo bottles, Styrofoam trays for ground beef, and coffee-cup lids, among other things.

Incorporate iodine-rich foods into your diet, including seafood, dairy, and cranberries. Iodine is a necessary ingredient for thyroid-hormone production, which helps bones and brains develop well.

Look for cosmetics that are "phthalate-free" and made without parabens, triclosan, or benzophenones.

Opt for naturally flame-resistant fibers, like wool, instead of chemically treated carpets, furniture, and clothes.

Circulate fresh air through your home.

Small steps like these can make a big difference. The European Union has banned 1,328 chemicals from cosmetic use, and under the new bans French scientists have noticed a decline in chemical concentrations in people's blood, urine, and hair. In the US, the FDA forbids just 11 chemicals, and concentrations of the toxic chemicals in American bodies are elevated when compared to Europeans.

The US has taken steps to improve public health before. The phase-out of leaded gasoline and paint in the 1970s led to a measurable brainpower boost in kids: as blood lead levels dropped, IQs went up anywhere from 2.2 to 4.7%. The economic benefits of that ban tally up to $2.45 trillion every year, and Trasande compares the IQ hike's impact on productivity and the economy to a generous stimulus package:

As Trasande writes, "Each of us 300 million Americans gets the equivalent of as much as a $1,000 tax refund each year because we did the right thing and got lead out of gasoline in the 1970s."

Many of the chemicals on Trasande's danger list today stay in the body for hours or days, not months or years, which means it's never too late to reduce your exposure.