Avoiding a chemical suspected to disrupt people’s hormones may be easier said than done, new research published in BMJ Open suggests. Despite following guidelines meant to reduce the amount of bisphenol A (BPA) in a person’s diet, about 90 percent of the people in the study still had traces of the chemical in their urine.

“It wasn’t that they weren’t trying to reduce their exposure, it’s just that by following the guidelines, nothing happened. Their exposure stayed the same,” Tamara Galloway, an environmental toxicologist at the University of Exeter and one of the authors of the paper, told Newsweek . The levels were still below the guidelines established by regulators, she noted.

The chemical, which can be found in some water bottles, food wraps and receipt papers, can cause “reproductive toxicity” in women, according to California’s Environmental Protection Agency. Specifically, it can disrupt hormone levels in a person’s body.

“Hormones are at the basis of the control of your sexual functions, your reproduction and your development. Hormones also control just about every other process in your body,” Galloway said. “If you have a substance that interferes with that hormone activity, then you want to be able to avoid that as much as possible.”

BPA’s health effects at high levels are pretty well-known. However, Galloway said, the potential effects of low levels of BPA is still controversial. Some studies have shown effects; others haven’t.

Galloway noted that her team’s work does not specifically look at health effects. It only looked at whether or not people could avoid even low levels of exposure by following recommendations issued by authorities to reduce BPA exposure.

Those recommendations typically include not microwaving plastic containers with the chemical, storing foods in glass containers, eating more fresh food and washing hands before eating to reduce your exposure.

However, even following those guidelines didn’t help—and they were extremely difficult to follow.

“It was almost impossible to know what your food had been packaged in at each stage,” Galloway said. “They might have avoided packaged food but then have been making a pizza with tinned tomatoes or packaged ingredients.”

In 2008, the Natural Resources Defense Council (NRDC) asked the Food and Drug Administration to ban the use of BPA in packages for human food. The agency denied the request four years later, stating that “the most appropriate course of action at this time is to continue scientific study and review of all new evidence regarding the safety of BPA.”

For those who do want to avoid BPA, better labeling might help, Galloway said. And following the guidelines is still a good idea. Nevertheless, she said, “you can choose to go organic, you can become a vegan, but according to this particular study, you couldn’t choose to be free of BPA in your diet.”