CARRS Pollutants Study

Nearly 20% of the 382 million adults with diabetes in the world live in India. While the contribution of risk factors such as unhealthy diets and physical inactivity to the diabetes epidemic has been evaluated, less traditional exposures such as persistent organic pollutants (POPs) remain unexplored. Epidemiological studies conducted largely in high-income countries have suggested an association of POPs, particularly polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides, with diabetes. The few surveillance studies available in India have not reported a decline in POPs levels in human serum over the past 30 years; thus, India is considered a “hot spot” for POPs exposure. Further, the phenotype of diabetes in Asian Indians differs from that of other ethnicities: diabetes occurs at a lower BMI and beta cell function declines at an earlier stage relative to insulin resistance in Asian Indians. This is of particular interest in considering the effects of POPs because animal studies suggest that these pollutants affect diabetes risk via action on beta cells. 

The CARRS (Centre for cArdiometabolic Risk Reduction in South-Asia) Study, an ongoing collaboration between Emory University, the Public Health Foundation of India, the Madras Diabetes Research Foundation, and the All India Institute of Medical Sciences, follows a representative cohort of 12,271 adults (≥ 20 years old) enrolled between 2010-2011 from two urban sites in India (Delhi and Chennai). This study aims to:

• standardize and cross-validate methods for mesausre the measuring the four most biologically relevant polychlorinated biphenyl (PCB) congeners and seven organochlorine pesticides or their metabolites in human serum
• use a nested case control study design in a prospective cohort of adults to estimate the association of the four PCB cogeners and seven organochlorine pesticides with incident diabetes. 

This study dysregulation will build laboratory capacity in India and uniquely position a team of diabetes and environmental pollutant experts in the U.S. and India to conduct the largest prospective analysis of the association between POPs and incident diabetes, furthering the world’s understanding of the role of these pervasive exposures in the diabetes epidemic.