Per-fluoroalkyl substances (PFAS) are persistent environmental pollutants that were used in a variety of products, including firefighting foams, non-stick cookware, dental floss, fire and chemical resistant tubing and more. When these PFAS chemicals are taken into the body (via exposure from water, food, clothing or other sources) their removal by the body is complex and can take up to 7 years (see Table 3) before the PFAS chemicals are removed. So what does PFAS do to your body? Exposure to these PFAS chemicals is known to increase your risk of various cancers, hypercholesterolemia, thyroid disease, proteinuria, kidney disease and colitis.

The purpose of this study was to replicate known associations reported in the literature using Electronic Health Records (EHR) data. Unlikely prior studies, our study utilizes data collected during routine clinical care. Exposure to PFAS in our study includes individuals living in a heavily exposed population outside of Philadelphia (Horsham-Warminster-Warrington) that is known to have some of the highest PFAS levels in the entire United States of America (USA). We were able to replicate known associations between PFAS exposure and many diseases, including hypercholesterolemia, thyroid diseases, and colitis. We describe some key findings below.

Intestinal Issues and Colitis: Prior research found an adjusted rate ratio of 1.76-2.86 for ulcerative colitis among PFAS exposed individuals. In our heavily exposed study population, we found that toxic gastroenteritis and colitis had an Odds Ratio (OR)=4.41 (p=0.014) and 'regional enteritis of unspecified site' had an OR=3.11 (p=0.003) indicated that gastrointestinal issues and colitis are at increased risk among heavily PFAS exposed individuals. 

Thyroid Disease: Previous studies have found links between various thyroid hormonal levels and PFAS exposure. In the literature associations were observed for women for thyroid disease (OR=1.64) and taking medications related to thyroid disease (OR=1.86) with slightly lower ORs for males⁴⁷. We found that malignant neoplasm of the thyroid gland was elevated among women with OR=3.23 (p<0.001) and primary hyperparathyroidism was also elevated with an OR=3.93 (p=0.021). We also found that unspecified acquired hypothyroidism was elevated with an OR=1.53 (p=0.002), which was closer in risk size to those reported in previous studies⁴⁷. Initially, it may seem conflicting that both hypothyroidism and hyperthyroidism condition codes demonstrated increased risk in our PFAS exposure sample. However, many individuals who are being treated for thyroid disease have either hypo- or hyper- thyroidism at various stages of their therapy while the medication levels are being titrated⁵⁸ This could be the reason for our findings, and future work involves including laboratory values and medication histories for more detailed exploration in these findings. Importantly, the extremely high OR for malignant thyroid cancer in our female population OR=3.23 indicates the important difference between studying PFAS exposure as an occupation as in other studies versus our population, which was heavily exposed to PFAS over a long period of time (but not necessarily an occupational exposure).

Overall our proof-of-concept study confirms that EHRs can be used to study human health and disease impacts of environmental disasters, such as PFAS exposure, and produces equivalent disease-exposure knowledge to prospective epidemiology studies while remaining cost-effective.