Both osteocalcin ) and CTx have been negatively associated with bone mineral density (BMD) in both men and women In addition, weak but significantly inverse associations have been found between total BMD and air pollution among 590 men 75 – 76 years old Based on these previously published studies, it is possible to hypothesize that exposure to ambient air pollution may cause an increase in bone turnover markers (osteocalcin and CTx).