When we’re warned about air pollution, we often think about the damage it might do to our lungs and health when we breathe it in. But there is a growing body of evidence that some pollutants found in the air, including a group of chemicals called phthalates, might be absorbed directly through the skin. A new study, published in the journal Environmental Health Perspectives, has found that the skin absorption of certain phthalates is comparable to that from inhalation.
Found in everything ranging from sex toys to paint, phthalates are ubiquitous throughout modern life. Known as “plasticizers,” they are often added to plastics to make them more flexible, transparent and durable, and have become the most widely used plasticizers in the world. They are, however, easily released from the products to which they are added, and are frequently leached into the environment. They’re so common in the air we breathe and specifically the food we eat, that according to the CDC, most Americans have measurable levels of phthalates in their urine.
While the Food and Drug Administration concludes that it’s “not clear what effect, if any, phthalates have on human health,” and that the levels detected in humans are too low to be of any concern, some studies have found selected phthalates to be associated with a range of conditions, from respiratory problems to diabetes. There has already been some suggestion that phthalates can be absorbed directly through the skin, so this new study looked at two of the most likely candidates: Diethyl phthalate (DEP) and di(n-butyl) phthalate (DnBP).
The researchers took six healthy men and put them into rooms for six hours at a time with elevated air concentrations of DEP and DnBP while only wearing shorts. To distinguish between absorption through the skin and through breathing, they did the experiment twice, once with a breathing hood that prevented inhalation of the spiked air, and once without. In addition to this, to try and limit the effect from phthalates naturally in the environment, the participants each went on a restricted diet and stopped using all cosmetics, including shampoos and deodorants, before each experiment.
The researchers found that absorption through the skin was actually greater than through inhalation for DEP, and around 80% of that seen from inhalation for DnBP. These results go to show that the absorption of specific air pollutants through our skin can be a major pathway for them getting into our body, and considering that the skin is our largest organ, this shouldn’t come as too much of a surprise. But caution should still be taken with this study, as the sample size of six was incredibly small and we’re yet to know if wearing anything more than shorts might impact on this absorption rate.
While the elevated concentrations of phthalates that the participants were exposed to might not be what people experience outside in real life, this study goes some way to show that while most assessments on the harm of air pollution only look at the impact of the pollutants when inhaled, this might not be enough.