Small-particle air pollution – or black carbon a pollutant linked to vehicle emissions and other products of combustion – may raise the risk of genetically vulnerable people developing glaucoma, according to a study out of Harvard Medical School in Boston.
“Oftentimes, when we think about glaucoma we think about risk factors like age and genetic predisposition and we don’t think about the environment,” said the study’s lead author, Jamaji Nwanaji-Enwerem, an MD/PhD candidate at the Harvard Medical School in Boston. “But one thing we’re starting to appreciate more is how the environment impacts health outcomes.”
Dr. Nwanaji-Enwerem and his colleagues looked at the effect of tiny particles of black carbon, which are smaller than 2.5 microns in diameter and can penetrate deep into the lungs, and from there, into the bloodstream.
To do this, they analysed data from 419 men with a mean (SD) age of 75.3 (6.9) years from the Boston area who had been participating since the 1960s in a larger US Department of Veterans Affairs aging study. The men had health exams every three to five years after joining the study and as part of those exams intraocular pressure was measured by Goldmann applanation tonometry.
But one thing we’re starting to appreciate more is how the environment impacts health outcomes
Validated spatiotemporal models were used to generate one year black carbon exposure levels at the addresses of the participants.
An independently developed genetic score approach was used to calculate allelic risk scores for three pathways associated with black carbon toxicity: endothelial function, oxidative stress, and metal processing. The associations among black carbon exposure, allelic risk scores, and intraocular pressure were explored using linear mixed-effects models.
Researchers notes the mean (SD) 1-year black carbon exposure was 0.51 (0.18) μg/m3, and the mean (SD) intraocular pressure for the left eye was 14.1 (2.8) mm Hg and for the right eye was 14.1 (3.0) mm Hg. Of the 911 visits, 520 (57.1 per cent) had a high endothelial function allelic risk score, 644 (70.7 per cent) had a high metal-processing allelic risk score, and 623 (68.4 per cent) had a high oxidative stress allelic risk score. In fully adjusted linear mixed-effects models, the association of black carbon with intraocular pressure was greater in individuals with a high oxidative stress allelic score (β = 0.36; 95% CI, 0.003-0.73) compared with individuals with a low score (β = −0.35; 95% CI, −0.86 to 0.15).
The authors concluded that “ambient black carbon exposure may be a risk factor for increased intraocular pressure in individuals susceptible to other biological oxidative stressors”.
Additional studies will need to be conducted and if the results are confirmed, they noted that ambient black carbon exposure and physiological oxidative stress should be monitored in an effort to prevent the development and progression of intraocular pressure–related disease.