Chromium and nickel are important soil pollutants in Taiwan. Previously, we showed that blood chromium levels correlated strongly with soil chromium levels. Our observation that many patients with dry eyes or a dry mouth came from areas where soils contain high chromium levels prompted us to investigate whether incidence and prevalence of SS are higher in areas where soils contain high levels of heavy metals.
We used a database from national health insurance (NHI) to study the epidemiology of SS. It was ascertained by at least 3 hospital visits with the diagnosis within 12 months. We then compared the results with the information about heavy metal contents in farm soils.
The incidence of SS was significantly increased (3.6 fold) in the areas where soils contained high levels of chromium and nickel. In contrast, lead, copper, or arsenic did not show such a strong association.
Both the prevalence and incidence of SS are significantly increased in areas where soils contain high levels of chromium and nickel. Whether heavy metal, particularly chromium or nickel is a novel environmental risk factor for sicca syndrome needs more studies to confirm.