OTCs and Humans
Organotin compounds are a class of compounds that contain the metal tin (Sn) bound to carbon atoms. The position of the tin within the molecule can significantly impact the compound’s characteristics. This variety of structures and characteristics makes organotins (OTCs) useful in a range of industrial applications, including plastic manufacturing, communications, and agriculture. They are also found in household products such as vinyl floor tile, wallpaper, diapers, and clothing.
However, OTCs pose risks to the environment. Since 2005, OTCs have been restricted from use in boat paint—previously one of their most widespread uses—because they can be toxic to marine wildlife. Their environmental persistence and potential for accumulation through the food chain create the potential for widespread exposure.
Animal studies have suggested that exposure to OTCs may be harmful to human health. However, there have been very few studies to measure their concentration in humans, or to directly measure their health effects. Additionally, such studies are often confounded because different forms of OTCs (e.g., tributyltin vs monobutyltin) can have different effects or levels of toxicity. Understanding the complex mixtures of chemicals present can be critical to understanding the findings.
Development to Analyze OTCs in Humans
In 2012, an international team of researchers, including the National Toxicology Program at NIEHS, sought to expand the base of available data on OTCs in humans by measuring their concentration in samples collected from a cohort of expectant mothers in the Danish Snart-Foraeldre/Milieu (Soon-Parents/Environment) study. Analysis of OTCs in humans is challenging due to potential tin contamination from the environment and from products used in the study. There was also a possibility of the OTCs degrading during storage and preparation, making it critical to use appropriate laboratory methods. Such studies require specialized equipment, facilities, and expertise to obtain accurate results.
RTI’s Analytical Science Laboratory has historically provided chemical analysis support for NTP, and so we worked to develop a method for analyzing six OTCs in serum. Existing methods were hazardous and labor-intensive; the direct chromatographic analysis method we developed is faster and easier while still measuring similar levels of OTCs.
After verifying that the method we developed was fit for our purpose, we used it on the Snart-Foraeldre/Milieu samples and found that the measured levels of OTCs were relatively low. The results indicated that exposure was low in the population studied, but the ongoing presence of OTCs in consumer products suggests that periodic monitoring may be helpful to ensure that this is still the case.
Building the Knowledge Base on OTC Exposure
While the development of the method was significant, a more far-reaching achievement of the Analytical Science Lab lies in the value of the data for future biomonitoring studies. A broader understanding of the effects of exposure to compounds requires many data points from a broad range of environments, communities, and populations. The results obtained here were in part due to close communication between RTI and our collaborators and the expertise of the Analytical Science researchers. The findings of this study can inform research on the effects of both individual compounds and on mixtures of compounds on human health.