Short-term effects of particle gamma radiation activities on pulmonary function in COPD patients

It is not known whether environmental gamma radiation measured in US cities has detectable adverse health effects. We assessed whether short-term exposure to gamma radiation emitted from ambient air particles [gamma particle activity (PRγ)] is associated with reduced pulmonary function in chronic obstructive pulmonary disease (COPD) patients.

We hypothesize that the inhalation of gamma radiation emitted from ambient air particles may be associated with reduced pulmonary function in individuals with COPD.

In 125 patients with COPD from Eastern Massachusetts who had up to 4 seasonal one-week assessments of particulate matter ≤2.5 μm (PM_2.5), black carbon (BC), and sulfur followed by spirometry. The US EPA continuously monitors ambient gamma (γ) radiation including γ released from radionuclides attached to particulate matter that is recorded as 9 γ-energy spectra classes (i = 3-9) in counts per minute (CPMγ) in the Boston area (USA). We analyzed the associations between ambient and indoor PRγi (up to one week) and pre and post-bronchodilator (BD) forced expiratory volume in 1 s (FEV₁) and with forced vital capacity (FVC) using mixed-effects regression models. We estimated indoor PRγi using the ratio of the indoor-to-outdoor sulfur in PM_2.5 as a proxy for infiltration of ambient radionuclide-associated particles.

Overall, exposures to ambient and indoor PRγi were associated with a similar decrease in pre- and post-BD FEV₁ and FVC. For example, ambient PRγ₃ exposure averaged from the day of pulmonary function testing through the previous 3 days [IQR of 55.1 counts per minute (CPMγ)] was associated with a decrease in pre-BD FEV₁ of 21.0 ml (95%CI: -38.5 to -3.0 ml; p < 0.01) and pre-BD FVC of 27.5 ml [95% confidence interval (CI): -50.7 to -5.0 ml; p < 0.01] with similar effects adjusting for indoor and outdoor BC and PM_2.5.

Our results show that short-term ambient and indoor exposures to environmental gamma radiation associated with particulate matter are associated with reduced pre- and post-BD pulmonary function in patients with COPD.