This post is the second in a series on insights into exposure assessment as presented at AIHce 2016 in Baltimore, Md. References to specific products or services do not constitute endorsement by AIHA or The Synergist.

In the world of occupational exposure assessments, dermal exposures are often overlooked, but as IH/OH professionals are turning to examine what may be on our skin, they’re also taking a closer look at the skin we’re in – specifically skin’s hydration and health and how those factors may impact exposure. The study and measurement of skin hydration is new to workplace safety, and the early findings and methods are fascinating.

“There are a number of things that can affect the condition of the skin and then, as a result, affect the ability of chemicals to be taken up through the skin. That’s a general rule,” said Jennifer Sahmel, MPH, CIH, CSP, the Principal Health Scientist for Cardno ChemRisk in Boulder, Colo., and a member of AIHA’s Dermal Exposure Subcommittee working group. “Healthy, intact skin is quite a good barrier for many substances, but not all. So it’s a very important factor in the result of dermal exposure.”

There are two key types of skin moisture measurements: transepidermal water loss (TEWL) and skin hydration or the hydration index (HI). Experts recommend that both measurements be collected concurrently in assessments, because they each measure different things. TEWL represents the diffusion of condensed water through the skin, basically measuring the skin’s ability to act as a moisture barrier, while skin hydration or HI is the water content of the skin. Although different, both measurements indicate the health of the skin. Altered skin barriers, weakened by disease or exposure to certain solvents, are often marked by elevated epidermal water loss, which correlates with low hydration.

Research reveals that TEWL values are higher on the palms (significantly higher than on other parts of the body) and, interestingly, are also higher on the dominant forearm. The baseline location for TEWL measurements is the middle of the forearm. Generally, TEWL values may fall slightly after age 60, and skin hydration decreases steadily with age.

“There are also some indications that when you have a compromised skin barrier, you will then open the individual up to not just increased exposure to liquids or solvents, but also particulates,” said Sahmel while presenting at AIHce 2016. “The evidence I’ve seen indicates that an intact skin barrier is an excellent barrier to ... particulates, including nanoparticles.”