Elevated Alu retroelement copy number among workers exposed to diesel engine exhaust

Abstract

A cross-sectional study of 54 male diesel engine exhaust (DEE)-exposed workers from an engine testing facility and a comparison group of 55 male unexposed controls was conducted in China. The association between occupational setting with high DEE exposure levels and Alu repeat copy number was investigated. Alu retroelements are repetitive DNA sequences that can multiply and compromise genomic stability. There is some evidence linking altered Alu repeats to cancer and elevated mortality risks. Personal air samples were assessed for elemental carbon, a DEE surrogate, using NIOSH Method 5040. Quantitative PCR was used to measure Alu repeat copy number relative to albumin (Alb) single-gene copy number in leucocyte DNA. DEE-exposed workers had a higher average Alu/Alb ratio than the unexposed controls. A positive exposure–response relationship (p=0.02) was observed. The Alu/Alb ratio was highest among workers exposed to the top tertile of DEE versus the unexposed controls. These findings suggest that DEE exposure may contribute to genomic instability.