The effects of particulate matter (PM), the mixture of particles in airborne pollution, on the body remains a major public health concern. This study investigates factors involved in toxicity from airborne particles and one molecular mechanism by which air pollution could lead to cardiovascular and cardiopulmonary disease.
Telomeres are repeated segments of DNA located at the ends of chromosomes, which protect the chromosome from deterioration. Telomere length (TL) is a biomarker of cardiovascular disease risk – individuals with shorter telomeres in their peripheral blood leukocytes show comparatively higher long-term risk of cardiovascular and respiratory disease.
Previous research indicates that increased oxidative stress and inflammation are two key pathways by which PM affects human health. The telomeric DNA regions appear to be particularly sensitive to modification by oxidative stress and inflammation, but whether PM exposure modifies TL had not been directly investigated. A team of researchers from the USA and China went to Beijing to explore this question.
Bejing, China is one of the most polluted cities in the world, with especially high traffic-derived air pollution due to very high population density, rapid increase in vehicular traffic, and limited emission control. Investigating individuals exposed to high levels of PM, such as those found in Beijing, may help to identify biomarker changes that might not be easily detectable in populations with lower exposure levels.
The research team was especially interested in investigating the time-dependent relationship of personal and ambient PM exposure measures with blood TL to see if there was a differential impact of short-term vs long-term exposure.
They looked at TL in blood samples from truck drivers and office workers in Beijing, measuring both personal PM exposure using lightweight monitors, and ambient PM levels from local monitoring stations. They estimated percent changes in TL relative to increases in PM exposure.
The team reported that their investigation provides evidence that short-term exposure to air pollution may increase TL, whereas longer exposure may lead to shorter TL. Both the rapid TL increase and the progressive time-dependent decrease in TL are potentially related to inflammatory and oxidative processes underlying the effects of PM on human health. Short-term exposure to ambient PM is associated with increased blood TL, consistent with TL roles during acute inflammatory responses. Longer exposures may shorten TL as expected after prolonged pro-oxidant exposures, indicating increased long-term risk of cardiovascular and respiratory disease
These findings, if confirmed in additional investigations, would substantially further our understanding of in-vivo TL biology and provide valuable information for the design and timing of blood sample collections for future studies of environmental effects on TL.
Air pollution exposure and telomere length in highly exposed subjects in Beijing, China: a repeated-measure study. Hou L, Wang S, Dou C, Zhang X, Yu Y, Zheng Y, Avula U, Hoxha M, Díaz A, McCracken J, Barretta F, Marinelli B, Bertazzi PA, Schwartz J, Baccarelli AA. Environ Int. 2012 Nov 1;48:71-7. PMID: 22871507