Ambient air pollution and diabetes in China
Authors: Angel M Dzhambov
Journal: The Lancet Planetary Health (2018)

Air pollution is increasingly in focus for diabetes epidemiology, accounting for roughly 40% of all studies that explore environmental determinants of diabetes.1Dendup T Feng X Clingan S Astell-Burt T Environmental risk factors for developing type 2 diabetes mellitus: a systematic review.Int J Environ Res Public Health. 2018; 15: 78Crossref PubMed Scopus (179) Google Scholar In The Lancet Planetary Health, Bo-Yi Yang and colleagues2Yang B-Y Qian Z Li S et al.Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health Study.Lancet Planet Health. 2018; 2: e64-e73Summary Full Text Full Text PDF PubMed Scopus (127) Google Scholar report on the association between air pollution and diabetes and glucose-homoeostasis markers in Liaoning province, China. Because more than 90% of all studies on this subject have been done in developed countries,1Dendup T Feng X Clingan S Astell-Burt T Environmental risk factors for developing type 2 diabetes mellitus: a systematic review.Int J Environ Res Public Health. 2018; 15: 78Crossref PubMed Scopus (179) Google Scholar the study by Yang and colleagues adds to the thin body of scientific literature coming from developing countries. China is not only known for its high concentrations of air pollution,3Guan W-J Zheng X-Y Chung KF Zhong N-S Impact of air pollution on the burden of chronic respiratory diseases in China: time for urgent action.Lancet. 2016; 388: 1939-1951Summary Full Text Full Text PDF PubMed Scopus (547) Google Scholar but also for the highest prevalence of diabetes worldwide, which affects more than 100 million people.4Yang W Lu J Weng J et al.Prevalence of diabetes among men and women in China.N Engl J Med. 2010; 362: 1090-1101Crossref PubMed Scopus (2683) Google Scholar, 5Wang L Gao P Zhang M et al.Prevalence and ethnic pattern of diabetes and prediabetes in China in 2013.JAMA. 2017; 317: 2515-2523Crossref PubMed Scopus (1220) Google Scholar In fact, diabetes mortality is highest in the north eastern region of China6Zhou M Astell-Burt T Yin P et al.Spatiotemporal variation in diabetes mortality in China: multilevel evidence from 2006 and 2012.BMC Public Health. 2015; 15: 633Crossref PubMed Scopus (16) Google Scholar where the study2Yang B-Y Qian Z Li S et al.Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health Study.Lancet Planet Health. 2018; 2: e64-e73Summary Full Text Full Text PDF PubMed Scopus (127) Google Scholar by Yang and colleagues took place. The authors found air pollutants to be consistently associated with higher prevalence of diabetes and higher concentration of glucose-homoeostasis markers.2Yang B-Y Qian Z Li S et al.Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health Study.Lancet Planet Health. 2018; 2: e64-e73Summary Full Text Full Text PDF PubMed Scopus (127) Google Scholar They also identified some potentially susceptible subgroups, namely younger and overweight individuals.2Yang B-Y Qian Z Li S et al.Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health Study.Lancet Planet Health. 2018; 2: e64-e73Summary Full Text Full Text PDF PubMed Scopus (127) Google Scholar The large and representative sample with a high overall response; rich set of air pollutants, confounders, and glucose-homoeostasis markers; and several definitions of diabetes considered in this work are clear strengths, but its cross-sectional design makes it difficult to establish a causal association. Notably, the diabetogenic effect in question is biologically plausible, and logic dictates the answer as to what came first in time—the exposure or the outcome: high concentrations of air pollution are more likely to have caused diabetes than for people with diabetes to have moved to a more polluted residential area. Another concern is the sampling strategy (participants were sampled from 33 communities, with only 11 air quality monitoring stations in the whole study area),2Yang B-Y Qian Z Li S et al.Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health Study.Lancet Planet Health. 2018; 2: e64-e73Summary Full Text Full Text PDF PubMed Scopus (127) Google Scholar which inhibited the use of more sophisticated methods for exposure assessment to capture between-participant differences on a fine spatial scale. However, that exposure misclassification arguably makes the results conservative and lends further support to Yang and colleagues's hypothesis. Faithful to biomedical reasoning, the authors explained the association they found with the hypotheses that air pollutants lead to oxidative stress and inflammation of adipose tissue, and subsequent insulin resistance, endoplasmic reticulum stress, and apoptosis.2Yang B-Y Qian Z Li S et al.Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health Study.Lancet Planet Health. 2018; 2: e64-e73Summary Full Text Full Text PDF PubMed Scopus (127) Google Scholar But these hypotheses might not be the whole picture and future research can expand this theory to include potential socioecological pathways. One review1Dendup T Feng X Clingan S Astell-Burt T Environmental risk factors for developing type 2 diabetes mellitus: a systematic review.Int J Environ Res Public Health. 2018; 15: 78Crossref PubMed Scopus (179) Google Scholar has elaborated on the capacity of people's physical environment to shape their behaviour and, hence, indirectly increase the risk of diabetes. For example, high concentrations of air pollution might inhibit restorative quality in the neighbourhood, and in turn, that might reduce the opportunities for outdoor recreation, social interaction, and commuting or leisure time physical activity,7Dzhambov A Hartig T Markevych I Tilov B Dimitrova D Urban residential greenspace and mental health in youth: different approaches to testing multiple pathways yield different conclusions.Environ Res. 2018; 160: 47-59Crossref PubMed Scopus (145) Google Scholar thereby raising the risk of diabetes. Simultaneously, cognitive stress due to air pollution, particularly in areas where people's awareness is high and has great personal salience,8Claeson AS Lidén E Nordin M Nordin S The role of perceived pollution and health risk perception in annoyance and health symptoms: a population-based study of odorous air pollution.Int Arch Occup Environ Health. 2013; 86: 367-374Crossref PubMed Scopus (106) Google Scholar might trigger series of neuroendocrine reactions leading to hyperglycaemia, systemic inflammation, insulin resistance, and ultimately, type 2 diabetes.9Kelly SJ Ismail M Stress and type 2 diabetes: a review of how stress contributes to the development of type 2 diabetes.Annu Rev Public Health. 2015; 36: 441-462Crossref PubMed Scopus (145) Google Scholar Future research should also consider how multiple environmental influences (eg, traffic noise, greenspace, walkability, and food environment) can work together with regards to modifying the determinants of diabetes.1Dendup T Feng X Clingan S Astell-Burt T Environmental risk factors for developing type 2 diabetes mellitus: a systematic review.Int J Environ Res Public Health. 2018; 15: 78Crossref PubMed Scopus (179) Google Scholar As a final point, it is conceivable that air pollution might not only increase the risk of diabetes, but also affect its progression; exploration of this hypothesis would be of particular value given the high prevalence of diabetes-related mortality in some regions of China.6Zhou M Astell-Burt T Yin P et al.Spatiotemporal variation in diabetes mortality in China: multilevel evidence from 2006 and 2012.BMC Public Health. 2015; 15: 633Crossref PubMed Scopus (16) Google Scholar Most public health decisions on environmental issues are made under uncertainty, especially when the stakes are high and prevention is better than cure.10Horton R The new new public health of risk and radical engagement.Lancet. 1998; 352: 251-252Summary Full Text Full Text PDF PubMed Scopus (38) Google Scholar In a time when daunting ecological threats tend to be dismissed in some public sector circles, evidence of even potentially detrimental metabolic effects of air pollution should be heralded and communicated to stakeholders to strengthen the societal impact of research. I have co-authored publications with some of the authors of the study. Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health StudyLong-term exposure to air pollution was associated with increased risk of diabetes in a Chinese population, particularly in individuals who were younger or overweight or obese. Full-Text PDF Open Access