Associations Between Atmospheric Ozone, P.M 2.5, and Incidence Rates of Adult Diabetes

Introduction: Fine particulate matter and ozone are naturally and anthropogenically produced in the atmosphere. Ozone is a secondary gaseous air pollutant formed from traffic-related precursors under the influence of sunlight. Particulate matter 2.5 (PM2.5) induces cytotoxicity, inflammation, oxidative stress, and alters gene expression. Approximately 34 million Americans in the United States have been diagnosed with diabetes. Additionally, over 1 million of the adult population in Georgia have been diagnosed with diabetes with an estimated cost of $11 billion in Georgia each year Increased diabetes prevalence rates have been reported to be associated with long-term exposure to air pollutants. These air pollutants released from long-term industrial exposures and exhaust from vehicles could be one of the major risk factors for the development of Type 2 diabetes, which is the leading cause of increasing premature deaths and global disease burden. Studies have also found that long-term exposure to that P.M2.5 and Ozone concentration can cause morbidity and mortality. This study aimed to examine the association between these two specific air pollutants and incident rates of adult diabetes at the county level. Methods: County-level data for ozone, PM2.5, adult Type 2 diabetes diagnosed patient numbers and other relevant confounding factors were collected from the Georgia Health Data Hub (2011-2018). The total number of counties analyzed in Georgia was 159. The dependent variable “Adults diagnosed with diabetes” was the total number of adults diagnosed with diabetes daily at County-level. The independent variable “Ambient daily ozone concentration” was reported by the county-level National Ambient Air Quality Standard (NAAQS) for ozone per million (ppm) averaged over 8 hours. The independent variable “PM2.5” was reported as the county-level mean annual concentration of smaller than 2.5 microns in aerodynamic diameter fine suspended particles. The first control variable was “percentage nonfarm” reported as a county-level percentage total number of nonfarm jobs. The second control variable, “percentage aged 25-44years” was county-level total percentages of people between the age group of 25-44 years. One sample KS (Kolmogorov–Smirnov test) was significant. Therefore, a negative binomial regression test was conducted to examine the association between the dependent variable- adults diagnosed with diabetes annual cases by county with total county population as the offset, and two independent county-level variables: ambient daily ozone concentration and P.M 2.5, while controlling for age and non-farm jobs. Finally, the incidence rates ratios (IRR) were also calculated. Result: The results show that at the County level, a 1% increase in ambient daily ozone concentration was associated with a 24% increase in adults diagnosed with diabetes (IRR=1.24, CI=1.09-1.41), and a 1% increase in the percentage of non-farm jobs was associated with 2% (IRR=1.02, CI=1.01-1.03) rise in adults diagnosed with diabetes. Similarly, a 1% increase in P.M 2.5 was associated with a 37% increase in adults diagnosed with diabetes (IRR=1.37, CI=1.06-1.76), 1% increase in the percentage of non-farm jobs was associated with 2% (IRR=1.02, CI=1.01-1.03) rise in the percentage of adults diagnosed with diabetes. Discussion: Our findings are consistent with the previous results reported from China and the United States suggesting that long-term ozone exposures could be associated with a higher incidence of type 2 diabetes. However, our findings suggest that ozone concentration and PM2.5 increase the risk for adults diagnosed with type 2 diabetes based on the calculated IRRs. In addition, the percentage of people with non-farm jobs exposed to ozone and PM2.5 had higher IRR values for adults with type 2 Diabetes. The limitation is that it is an ecological study and that there may be other confounders that were not identified which may affect the outcome. Additionally, County-level exposure may not accurately reflect individual exposures because ambient air pollution interventions are likely to happen at the community level rather than at the individual level, which may not address the individual exposure-outcome response. Conclusion: This study provides evidence of significant associations between two specific air pollutants (i.e., PM2.5 and ozone concentrations) and IRR of adults with type 2 diabetes. The findings are important because the evidence regarding the contribution of air pollution to the diabetes burden in Georgia is lacking and people with non-farm jobs exposed to these specific air pollutants have higher chances of developing type 2 diabetes. It is essential that further research needs to be conducted on the biological mechanisms of the association between these specific air pollutants and type 2 diabetes development. Stakeholders in the governing agency should review air pollutants regulations policies to limit the exposures of these two air pollutants among the diabetic worker population in Georgia