Urban Air Pollution and Insulin Resistance, Type 2 Diabetes, and Obesity

Longitudinal trial supports evidence for association

By Walter Crinnion, ND

Reference

Alderete TL, Habre R, Toledo-Corral CM, et al. Longitudinal associations between ambient air pollution with insulin sensitivity, β-cell function, and adiposity in Los Angeles Latino children [published online ahead of print January 30, 2017]. Diabetes.

Objective

To confirm epidemiological finding that ambient air pollutants are linked to higher risk for type 2 diabetes mellitus (T2DM)

Design

Longitudinal trial

Participants

Three-hundred and fourteen Latino youth, between 8 and 15 years of age, in the Los Angeles area who participated in the Childhood Obesity Research Center Air Study; all participants were either overweight or obese. These children were recruited between 2001 and 2012 and were followed for an average of 3.4 years. None of those included in the study were diabetic (assessed by an oral glucose tolerance test) or were on any medication that would affect insulin or glucose tolerance.

Study Parameters Assessed

Levels of ambient air pollutants including nitric oxide, nitrogen dioxide (NO2), and particulate matter less than 2.5 microns (PM2.5) were estimated by utilizing data collected from monitoring stations in the Los Angeles area. Monthly average exposure levels were calculated from daily values and based on the distance from the measuring stations (using a distance-squared weighting algorithm).

Clinicians need to start paying attention to the myriad adverse health effects from simply breathing air in any metropolitan area.

Insulin sensitivity was assessed with a 13-sample insulin-modified frequently sampled intravenous glucose tolerance test. Data from this test provided a rating for whole body insulin sensitivity (Si), acute insulin response to glucose (AIRg), and assessment of beta cell function (disposition index [DI]). Body mass index (BMI) was also measured throughout the study.

Primary Outcome Measures

Primary outcome measures included:

  • Whole body insulin sensitivity
  • Acute insulin response to glucose
  • Beta cell function
  • Adiposity

Key Findings

Both PM2.5 and NO2 were independently associated with statistically significant reduction in insulin sensitivity; NO2 was associated with a statistically significant decline in beta cell function. Both PM2.5 and NO2 were associated with a statistically significant increase in BMI.

Practice implications

Lifestyle approaches for the prevention and treatment of insulin resistance, metabolic syndrome, and T2DM are typically focused on diet and exercise to reduce the number of calories going in and increase the number of calories being burned. Yet a number of environmental pollutants have been clearly linked to increased risk for T2DM including persistent organic pollutants and arsenic.

Over the last decade articles have begun to associate vehicular exhaust—ambient air pollution commonly elevated in all urban areas across the globe—with metabolic abnormalities. In the last 7 years several studies have demonstrated that adults and youth who are exposed to higher levels of nitric oxide, NO2, and PM2.5 had higher rates of T2DM. Three studies have demonstrated that children and adults with increased exposure to vehicular exhaust had higher calculated insulin resistance (using the homeostatic model assessment of insulin-resistance [HOMA-IR]).1-3 Since HOMA-IR results are not always confirmed with glucose tolerance testing, this longitudinal study was done.

This new study adds to accumulating evidence that urban air pollution is associated with insulin resistance, beta cell function, and adiposity. Clinicians need to start paying attention to the myriad adverse health effects from simply breathing air in any metropolitan area. Air purification units for the home that force air through a series of filters to remove particles down to 1 micron should be on the list of “must haves” for all patients, right next to water filters, organic varieties of “the dirty dozen” (most toxic fruits and vegetables), and exercise.

About the Author

Walter J Crinnion, ND, has specialized in environmental medicine for the last 30 years. He currently provides a monthly podcast, CrinnionOpinion, to keep practitioners current in environmental medicine and has a 12-month training program for those who wish to gain expertise in this field.

References

  1. Chen Z, Salam MT, Toledo-Corral C, et al. Ambient air pollutants have adverse effects on insulin and glucose homeostasis in Mexican Americans. Diabetes Care. 2016;39(4):547-54.
  2. Toledo-Corral CM R, Berhane K, et al. Effects of air pollution exposure on glucose metabolism in Los Angeles minority equally to this work. Pediatr Obes. 2016. doi: 10.1111/ijpo.12188. [Epub ahead of print]
  3. Thiering E, Cyrys J, Kratzsch J, et al. Long-term exposure to traffic-related air pollution and insulin resistance in children: results from the GINIplus and LISAplus birth cohorts. Diabetologia 2013;56(8):1696-1704.