The new study, published in Environmental Health Perspectives, looked at organophosphate flame retardants, which are fire-preventing chemicals found in a lot of different items we use every day. PFRs, as they're known, are found all over the place, from baby products to yoga mats, dyes, textiles, upholstered furniture, and car interiors. They're very widely used in part because another kind of flame-retardant chemical, known as polybrominated diphenyl ethers (try saying that four times fast), was found to be bad for the environment and had its use vastly cut down.

The new flame retardants in use, it turns out, aren't too benign, either. They easily come loose from the materials they're put into, and can be found in high concentrations in urine, blood, even breast milk among humans who spend time with PFR-heavy products (i.e., most of us). A study in 2015 also found that women tend to have twice the urinary levels of one type of PFR compared to men, which the scientists called "very unusual." They hypothesize that it might be due to PFRs showing up in some kind of feminine hygiene product, but they don't know which one it might be. That wouldn't be a problem of itself, but PFRs in the body have been linked to some particularly problematic nasties: there's increasing evidence that they're endocrine disruptors, interfering with the body's hormonal balance, and that they create problems with male sperm count.

So where do women trying to get pregnant come in? The scientists behind the new study wanted to see whether exposure to PFRs did anything to the success of IVF cycles, so they recruited 211 women, all of whom had had at least one test of PFRs, levels while they were undergoing an IVF cycle. They were on average 35 years old and non-smokers, and were trying very hard to get pregnant. The results weren't great.

According to the study, the higher the levels of PFRs, the lower the levels of successful fertilization (a 10 percent decrease), implantation (31 percent decrease), pregnancy (41 percent decrease), and live birth (38 percent decrease). Two PFRs were particularly problematic: diphenyl phosphate and isopropylphenyl phenyl phosphate. The higher the levels of those chemical in the body, the less likely women were to have success at any of the points in the IVF cycle. If women undergoing IVF had high levels of PFRs overall in their systems, their likelihood of a live birth was 30 percent; if they had low levels, the likelihood jumped to 48 percent.

So what does this mean for women trying to get pregnant, using IVF or beyond?

The limit of this study, as the scientists pointed out, was that it didn't assess the PFR levels of any of the men involved; we know exposure might cause difficulties for male fertility, so it's unclear whether the problems were all women's PFR levels or were a combined effort. Either way, though, the link is worrisome.

The difficulty with this sort of scientific result is twofold: One, it's very hard to avoid PFRs in everyday life, and two, we don't know how the mechanism that might make pregnancies less viable with high PFR levels in the body actually works. The ubiquity of PFRs basically everywhere is backed up by the scientific literature: A study of pregnant women in North Carolina in 2016 found that every single one of them had traces in their urine. It seems that we inhale PFRs in dust a lot of the time, but they also pop up in high levels in wastewater around the world. But, as Popular Science explains, simply attempting to avoid PFRs altogether isn't realistic:

"Flame retardants are so ubiquitous because safety standards all over the world require lots of furniture, clothing, building materials, and electronics to be flame retardant. The easiest way for companies to do that is often to add a flame retardant chemical, so they do. From there, you can absorb the compounds through the food you eat and the air you breathe."

So what can you do if you want to avoid these chemicals? Well, for one, more scientific analysis needs to be done, on many levels. At the moment, all we have is a correlation between high PFR levels and pregnancy problems — and we can't really tell if the problems extend past IVF to women's fertility in general. Working out the mechanisms through which exposure to flame retardants might actually mess with fertility outcomes is the key to trying to combat the problem.

It's also important to remember that the chemicals that PFRs were brought in to replace were also found to be a possible cause of fertility issues. It's often difficult for companies to test the effects of chemical exposure on fertility in women because of the ethical issues involved in testing on humans, and tests on animals can only provide blueprints. So while it's possible to hope for the development of a new flame retardant that doesn't affect fertility, that day may be a long way off, and we've still got to cope with the onslaught of everyday PFRs right now. Be aware of what's around you, try to find materials that haven't been PFR-treated — and be exceptionally careful about using fire around them.