Recent exposure to particle radioactivity and biomarkers of oxidative stress and inflammation: The Framingham Heart Study

Abstract

Background: Decay products of radioactive materials may attach to ambient fine particles and form radioactive aerosol. Internal ionizing radiation source from inhaled radioactive aerosol may contribute to the fine particulate matter (PM_2.5)-inflammation pathway. However, few studies in humans have examined the associations.

Objectives: To examine the associations between particle radioactivity and biomarkers of oxidative stress and inflammation among participants from the Framingham Offspring and Third Generation cohorts.

Methods: We included 3996 participants who were not current smokers and lived within 50 km from our central air pollution monitoring station. We estimated regional mean gross beta radioactivity from monitors in the northeastern U.S. as a surrogate for ambient radioactive particles, and calculated the 1- to 28-day moving averages. We used linear regression models for fibrinogen, tumor necrosis factor α, interleukin-6, and myeloperoxidase which were measured once, and linear mixed effect models for 8-epi-prostaglandin F_2α, C-reactive protein, intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), P-selectin, and tumor necrosis factor receptor-2 that were measured up to twice, adjusting for demographics, individual- and area-level socioeconomic positions, time, meteorology, and PM_2.5. We also examined whether the associations differed by median age, sex, diabetes status, PM_2.5 levels, and black carbon levels.

Results: The mean age was 54 years and 54% were women. An interquartile range (3 × 10^-3 pCi/m³) higher beta radioactivity level at the 7-day moving average was associated with 5.09% (95% CI: 0.92, 9.43), 2.65% (1.10, 4.22), and 4.71% (95% CI: 3.01, 6.44) higher levels of interleukin-6, MCP-1, and P-selectin, but with 7.01% (95% CI: -11.64, -2.15) and 2.70% (95% CI: -3.97, -1.42) lower levels of 8-epi-prostaglandin F_2α and ICAM-1, respectively.

Conclusions: Regional mean particle radioactivity was positively associated with interleukin-6, MCP-1, and P-selectin, but negatively with ICAM-1 and 8-epi-prostaglandin F_2α among our study participants.

Keywords: Environment; Epidemiology; Gross beta radiation; Inflammation; Oxidative stress; Particle radioactivity.

Figure 1.. Map of the study region showing the distribution of the study participants and the locations of monitors.

To protect the confidentiality of the participants, the residential locations on the map were masked by altering the longitude and latitude by a small random amount. Thus, although these locations are representative of the distribution of participants’ residential locations, none of them represent actual residential locations of the study participants. Circle indicates the 50 km radius from Supersite. Dots: residential locations of the study participants.

Figure 2.. Associations of 1- to 28-day moving averages of gross beta radioactivity with (A) interleukin-6, (B) MCP-1, (C) P-selectin, (D) CRP, (E) 8-epi-PGF_2α, (F) ICAM-1, (G) fibrinogen, (H) MPO, (I) TNF-α, and (J) TNFR-2 from participants of the Framingham Offspring and Third Generation cohorts.

Models were adjusted for centered age and (centered age)²; sex; body mass index; cigarette smoking status; cigarette pack-years; alcohol intake; educational level; median household income in the participant’s census tract from U.S. Census 2000 data; linear term of examination date, day of week of examination date, and sine and cosine term of the examination date; temperature and relative humidity; and PM_2.5. We added an examination identifier for 8-epi-PGF_2α, CRP, fibrinogen, ICAM-1, interleukin-6, MCP-1, Pselectin, and TNFR-2. Results were scaled by 3×10⁻³ pCi/m³. Error bars indicate the 95% confidence intervals.

Figure 3.

Associations of 1- to 28-day moving averages of gross beta radioactivity with (A) TNFR-2 by median age, and of (B) CRP and (C) P-selectin by diabetes status. Models were adjusted for centered age and (centered age)²; sex; body mass index; cigarette smoking status; cigarette pack-years; alcohol intake; educational level; median household income in the participant’s census tract from U.S. Census 2000 data; linear term of examination date, day of week of examination date, and sine and cosine term of the examination date; temperature and relative humidity; and PM_2.5; and an exam identifier. Results were scaled by 3×10⁻³ pCi/m³. Error bars indicate the 95% confidence intervals.