Analysis of gross alpha, gross beta activities and beryllium-7 concentrations in surface air: their variations and statistical prediction model

Measurements of Gross α- and β-Activities of Archived PM2.5 and PM10 Teflon Filter Samples

The adverse effects of ambient particulate matter (PM) on human health have been well demonstrated, but the underlying properties responsible for its toxicity are still unclear. We hypothesized that particulate radioactivity, which is due to the attachment of radioactive nuclides on particle surfaces, may be responsible for part of PM toxicity. We measured the gross α- and β-activities for daily PM_2.5 and PM₁₀ filters collected at the Harvard Supersite in downtown Boston from 2005 to 2006 and calculated the radioactivities at the time of air sampling retrospectively based on a previously established formula. We examined the relationship between different radioactivities and compared our measurements to those measured at the Boston EPA RadNet Station. The results showed that the majority of PM₁₀ radioactivity is associated with that of PM_2.5 samples for both α-activity (98%) and β-activity (83%). A strong linear relationship was observed between the α- and β-activities for both PM_2.5 [slope = 0.47 (±0.03); p-value < 0.0001] and PM₁₀ [slope = 0.46 (±0.09); p-value < 0.0001] samples. Measurements at the Harvard Supersite and at EPA RadNet sites are highly correlated for both α-activities [slope = 0.17 (±0.02), p-value < 0.0001] and β-activities [slope = 0.30 (±0.05), p-value < 0.0001]. Additionally, we identified several significant predictors for PM_2.5 α-activities. This novel method we developed to measure α- and β-activities from archived filters will make it possible to assess the retrospective particle radioactivity exposure for future epidemiological studies.

Exposure to Particle Beta Radiation in Greater Massachusetts and Factors Influencing Its Spatial and Temporal Variability

Particle radioactivity is a property of airborne particles caused by the presence of naturally occurring or anthropogenic radionuclides. Recent studies have found associations between particle radioactivity and adverse health outcomes, including changes in blood pressure and lung function. However, the spatiotemporal distribution of particle radioactivity and factors influencing its variability have not been extensively studied. We address these knowledge gaps using measurements of gross beta activity, collected at seven Environmental Protection Agency (EPA) RadNet monitors located in and around Massachusetts. We apply back-trajectory analysis to identify prevailing air mass trajectories and find that these trajectories strongly influence seasonal trends in beta activity. We also evaluate the effects of different meteorological predictors on daily beta activity concentrations using a mixed-effect model. Important predictors of beta activity include air mass trajectories, temperature, and relative humidity. Finally, we create a series of random forest models to impute missing beta activity concentrations at each RadNet monitor for use in future health studies. This is the first study to analyze spatiotemporal trends in particle radioactivity using measurements from the EPA RadNet system.

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

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 (PM2.5)-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 F2α, 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 PM2.5. We also examined whether the associations differed by median age, sex, diabetes status, PM2.5 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 F2α 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 F2α among our study participants.

Analysis of the evolution of gross alpha and gross beta activities in airborne samples in Valencia (Spain)

Gross alpha (A_α) and gross beta activities (A_β) were measured weekly in the airborne of the Universitat Politècnica de Valencia campus (in the east of Spain) during the period 2009-2015 (7 years). The geometric mean values of weekly A_α and A_β were 0.53·10^-4 Bq m^-3 and 5.77·10^-4 Bq m^-3, respectively; with an average ratio A_α/A_β of 0.097. This study highlights the heterogeneity of gross alpha and gross beta activities depending on the different periods of the year. Data show seasonal variations with the highest activity in summer months and the lowest one in winter months. Several atmospheric factors were considered in order to explain this intra-annual variation (wind speed, temperature, relative humidity, precipitations, dust content and prevailing wind directions). Multiple Linear Regression Analysis were performed in order to obtain information on significant atmospheric factors that affect gross α and gross β variability, which could be useful in identifying meteorological or atmospheric changes that could cause deviations in gross α and gross β activity depending on the seasons considered. Models obtained explain more than 60% of variability for global data, and also for winter and spring-autumn months. However, more research is needed to explain gross α and gross β variability in summer months, because the atmospheric factors considered in the MLR explain less than 35% of variability.

The effects of large-scale atmospheric flows on berylium-7 activity concentration in surface air

Understanding the exchange mechanism between stratosphere and troposphere is one of the most important concerns of meteorologists and climatologists for decades. Different methods are being adopted to study those mechanisms. One of those methods is the study upon the tropospheric concentration of conserve or passive entities with stratospheric origin. One of those passive entities is (7)Be that is produced upon the incident of cosmic rays on light atmospheric nuclei in the stratosphere. The availability of 5 years observations of (7)Be concentration in surface air in Tehran (35 degrees 41(') N, 51 degrees 18(') E) encouraged us to investigate meteorological condition effect on the surface concentration of (7)Be. Also, the intention was to see if there was any intrusion of stratospheric air into the troposphere at the time of high surface concentration of (7)Be and scavenging mechanism when the concentration was low. During the course of this study, it has been found that (7)Be concentration is high whenever there is a jet stream over Tehran. Since high-level jet streams normally form near tropopause folding, it could be interpreted as a sign of the intrusion of stratospheric air into the troposphere. It was also found that high concentration of (7)Be in the Tehran surface air in summer is associated with an upper ridge on 500 hPa surface located east of the city, and low concentration in winter is associated with an upper trough. The latter normally is seen whenever there is precipitation that suggests wet scavenging could be the reason for that observed low concentration.