Aside from inhalation, exposure to indoor air pollutants through skin and oral routes can also be significant. Exposure through skin and oral routes become important for lower volatility chemicals like methamphetamine, phthalates, and nicotine. In the March 22 SOCAAR Seminar Dr. Glenn Morrison, a professor at Missouri University of Science & Technology, spoke about the influence of clothing on exposure to methamphetamine, phthalates and nicotine.
The motivation behind investigating the exposure to methamphetamine stems from the large number of methamphetamine contaminated buildings across the United States and Canada, associated with methamphetamine production. Even after a former methamphetamine producing lab is cleaned up, residual contaminants can stay in the building. It can accumulate on fabrics and toddlers can ingest a substantial dose just by putting exposed fabric in their mouths.
Experimental data show that fabrics absorb contaminants and can accumulate quite a bit (multiple house volumes worth) of methamphetamine over time. There is also a significant difference in the amount absorbed by different materials like cotton and polyester because the absorption increases in more porous fabrics like cotton. However, good clean-up and periodic air concentration sampling can reduce the exposure to methamphetamine contamination. Moreover, it’s believed that methamphetamine in a building will decay over a few years’ time.
Other chemicals such as phthalate compounds have also been found in the bloodstream. The most commonly reported phthalate compounds were the flame retardants used in children’s clothing as well permethrin, an insecticide applied to military uniforms. Phthalate compounds are suspected to be linked to human testicular cancer, insulin resistance, feminization of males, abdominal syndrome.
In the talk, findings on an exposure study to phthalates compared between bare skin and clothed individuals in a controlled indoor environment were presented. The study found that the same amount of phthalate gets absorbed through skin as breathing. Furthermore, the age of an individual also influenced the uptake of phthalate. It was found that clean clothes were protective against dermal uptake of phthalates when compared to bare-skinned individuals. But clothes exposed to phthalates dramatically increased the dermal uptake of it.
Nicotine is another chemical that’s readily absorbed through the skin. But skin pH and ionization may slow its uptake. Results similar to the phthalate study were found in experiments with nicotine where clothing also contribute to dermal dose in tobacco smoke or vaping environments. Overall, the studies indicate that clothing can contribute to phthalate and other chemical absorption into the human body.