Is telomere length in buccal or salivary cells a useful biomarker of exposure to air pollution? A review

Telomeres are repetitive DNA-protein sequences located at the end of chromosomes and play an essential role in preserving information in our genome by protecting against end-to-end fusion, nucleolytic degradation, breakage, and inappropriate recombination. The telomeres shorten with aging and this process can be affected by oxidative stress and inflammation. Environmental and occupational factors may contribute to telomere length (TL) shortening, as demonstrated by an increasing number of studies. In particular, air pollution was associated with aging-related health outcomes and molecular alterations, such as telomeric shortening. Leukocytes are widely used for TL measurement. However, buccal and salivary cells have more intimate contact with airborne pollutants and are easier to sample. The objective of this review was to identify whether salivary or buccal TL represents a valid marker for evaluating the effects of pollution on health. The reviewed studies investigated the association between TL and occupational exposure (genotoxic substances in mechanical workers, and pesticides in pesticides applicators), residential traffic exposure (NOx, NO2, PM2.5, PM10, and black carbon), and household air pollution (PM2.5 and black carbon from biomass stoves). The studies involved adults and children. Although few studies have yet been carried out, almost all reported a negative association between salivary or buccal TL and exposure to air pollutants stating that it could be a good indicator of occupational or airborne pollution exposure. However, further research is needed to evaluate the effect of acute versus long-term exposure on salivary or buccal TL as well as the role of confounding factors. Moreover, most of the reviewed studies were conducted on healthy adults, so it is important to deeply investigate how TL is associated with all-cause mortality such as cancer, diabetes, cardiovascular disease, and respiratory disease, how it can be affected during childhood, and which changes over time can be associated with diseases’ onset in adulthood.