Exposure to radionuclides in smoke from vegetation fires

Assessment of Be-7, Pb-210 and Po-210 Activities in Airborne Particulate Matter Over Istanbul, Türkiye

Airborne particulate matter is one of the air pollutants which can have detrimental health effects in the human body. Radionuclides adsorb onto air particles and make their way to humans primarily through inhalation. Naturally-occurring radionuclides, 210Pb and 210Po, are of notable health concern due to their relatively elevated ingestion and inhalation doses. In the current study, activity concentrations of 7Be, 210Pb and 210Po were determined in air particulate matter (PM). PM2.5 was collected on the European side, while PM10 was collected on the Anatolian side of Istanbul. Be-7, 210Pb and 210Po activities were found to be 5.17 ± 2.35, 0.96 ± 0.42; 0.25 ± 0.14 mBq m- 3 in Anatolian side, respectively. Be-7, 210Pb and 210Po activities were found to be 3.81 ± 2.27, 0.62 ± 0.29, 0.29 ± 0.26, mBq m- 3 in European side, respectively. The ratio of 210Po/210Pb was found to be higher (0.47 ± 0.31 for PM2.5 and 0.34 ± 0.27 for PM10) than the global average of 0.1. This result can be explained by the fact that Po is more volatile than Pb and enhanced in the air by the combustion process. Inhalation dose rates of 210Pb and 210Po due to PM10 exposure were calculated to be 7.70 ± 3.30 and 4.05 ± 2.31 µSv year- 1, respectively. Pb-210 bioaccessibility was assessed by the extraction of the particles in simulated lung fluids. Approximately 24.8% of inhaled 210Pb was estimated to be bioaccessible. This study suggests that 210Po and 210Pb activities are partially enhanced in the air particles in Istanbul and should be regularly monitored.

A sensitive method to determine 210Po and 210Pb in environmental samples by alpha spectrometry using CuS micro-precipitation

A new sensitive method to determine polonium-210 (210Po) and lead-210 (210Pb) in a diversity of environmental samples was developed. For fresh and marine waters, Po was pre-concentrated using a titanium (III) hydroxide (Ti(OH)3) co-precipitation. Solid environmental samples were digested with nitric acid (HNO3) and hydrogen peroxide (H2O2). The alpha thin layer source was prepared using CuS micro-precipitation and 210Po was measured by alpha spectrometry. Lead-210 was left to decay for up to a year and indirectly measured via its progeny, 210Po. The chemical recoveries for 210Po and 210Pb were high, 90% and 97%, respectively, for a large variety of samples and a very low minimum detectable activity (MDA) was obtained. The method was validated using standardized solutions and certified reference materials.

Enhanced Polonium Concentrations in Aerosols from the Gulf Oil Producing Region and the Role of Microorganisms

This study provides the first data set of 210Po and 210Pb activity concentrations in the organic and inorganic components of several particle size classes of aerosols collected at two sampling stations in Kuwait. The 210Po concentrations in the aerosols (Bq/g) were similar in all of the particle size classes, but as most (91%) of the aerosol load was made of fine fraction particles of PM0.39-2.5 µm, most of the 210Po activity was carried by this aerosol fraction. At the two sampling stations, the 210Po/210Pb activity concentration ratios in the aerosols were similar, stable around the year, and averaged 1.5 (range 1.2-1.9), much higher than the typical activity concentration ratios of these radionuclides in unmodified (background) aerosols, with Po/Pb < 0.1. The aerosol enrichment in 210Po was likely originated from the oil industry, specifically by gas flaring and oil refining in the Gulf region. Radionuclide analysis in the organic and inorganic components of aerosols showed that the 210Po concentration in the organic component was one order of magnitude higher than the 210Po concentration in the inorganic component, in contrast with 210Pb, which displayed similar concentrations in both organic and inorganic aerosol components. The 210Po carrying organic component of aerosols was investigated and it was found to be largely composed of microorganisms with high microbial and fungi diversity, with the phyla Proteobacteria, Ascomycota, and Basidiomycota being dominant among the bacteria and with Zygomycota being dominant among the fungi. Therefore, we are facing an active concentration process of the atmospheric 210Po carried out by microorganisms, which underlies the 210Po enrichment process in the organic component of aerosols. This bioconcentration of polonium in bioaerosols was unknown.

Europe-Wide Atmospheric Radionuclide Dispersion by Unprecedented Wildfires in the Chernobyl Exclusion Zone, April 2020

From early April 2020, wildfires raged in the highly contaminated areas around the Chernobyl nuclear power plant (CNPP), Ukraine. For about 4 weeks, the fires spread around and into the Chernobyl exclusion zone (CEZ) and came within a few kilometers of both the CNPP and radioactive waste storage facilities. Wildfires occurred on several occasions throughout the month of April. They were extinguished, but weather conditions and the spread of fires by airborne embers and smoldering fires led to new fires starting at different locations of the CEZ. The forest fires were only completely under control at the beginning of May, thanks to the tireless and incessant work of the firefighters and a period of sustained precipitation. In total, 0.7-1.2 TBq ¹³⁷Cs were released into the atmosphere. Smoke plumes partly spread south and west and contributed to the detection of airborne ¹³⁷Cs over the Ukrainian territory and as far away as Western Europe. The increase in airborne ¹³⁷Cs ranged from several hundred μBq·m^-3 in northern Ukraine to trace levels of a few μBq·m^-3 or even within the usual background level in other European countries. Dispersion modeling determined the plume arrival time and was helpful in the assessment of the possible increase in airborne ¹³⁷Cs concentrations in Europe. Detections of airborne ⁹⁰Sr (emission estimate 345-612 GBq) and Pu (up to 75 GBq, mostly ²⁴¹Pu) were reported from the CEZ. Americium-241 represented only 1.4% of the total source term corresponding to the studied anthropogenic radionuclides but would have contributed up to 80% of the inhalation dose.

GIS-Based Forest Fire Risk Model: A Case Study in Laoshan National Forest Park, Nanjing

Fire risk prediction is significant for fire prevention and fire resource allocation. Fire risk maps are effective methods for quantifying regional fire risk. Laoshan National Forest Park has many precious natural resources and tourist attractions, but there is no fire risk assessment model. This paper aims to construct the forest fire risk map for Nanjing Laoshan National Forest Park. The forest fire risk model is constructed by factors (altitude, aspect, topographic wetness index, slope, distance to roads and populated areas, normalized difference vegetation index, and temperature) which have a great influence on the probability of inducing fire in Laoshan. Since the importance of factors in different study areas is inconsistent, it is necessary to calculate the significance of each factor of Laoshan. After the significance calculation is completed, the fire risk model of Laoshan can be obtained. Then, the fire risk map can be plotted based on the model. This fire risk map can clarify the fire risk level of each part of the study area, with 16.97% extremely low risk, 48.32% low risk, 17.35% moderate risk, 12.74% high risk and 4.62% extremely high risk, and it is compared with the data of MODIS fire anomaly point. The result shows that the accuracy of the risk map is 76.65%.

Gis and fuzzy logic applied to modelling forest fire risk

Fire risk mapping is a basic planning and protection element. This study presents the application of fuzzy logic in a geographic information system (GIS) as an alternative multi-criteria analysis for determining the areas of highest risk of forest fire in natural forest remnants in the Brazil. In the decision-making process, a set of factors that are relevant to fire safety were identified in the study area. For each input variable chosen for the model, a pertinence function was defined that best described its influence on fire risk. Subsequently, the variables were combined for the presentation of the final fire risk map. Concluded in the study that an increased risk of fire occurs at the wildland - urban interface. A strong relationship was observed between the fire ignition points and proximity to roads and urban areas. The proposed model was efficient to integrate the variables and determine areas of greatest risk.

Transfer of radionuclides from soil to Acacia auriculiformis trees in high radioactive background areas in North Vietnam

The Acacia auriculiformis is a tree common in tropical Asian countries, capable of growing in many different soil types, so it could be used for biomonitoring for high natural radionuclide areas in tropical and subtropical climates. The transfer factor (TF) of radionuclides from soil to A. auriculiformis in eight uranium and rare earth element (REE) mining areas of North Vietnam was investigated. The activity concentrations ²²⁶Ra, ²³⁸U, ¹³⁷Cs, ²²⁸Ra, and ⁴⁰K in both soil and A. auriculiformis showed considerable variation. The TFs of these radionuclides also varied in a wide range. In most of the eight areas, the highest TF was observed for ¹³⁷Cs and ²²⁸Ra. While the TFs for ²²⁶Ra and ²³⁸U were smallest. In addition, the TFs for radionuclides near REE mines were similar to those observed near uranium mines. The TFs for A. auriculiformis were within the ranges of TF reported for other plants, except for ¹³⁷Cs.

210Po concentration in different size fractions of aerosol likely contribution from industrial sources

²¹⁰Po, being a highly radiotoxic isotope, could contribute to significant inhalation dose to humans. This study establishes the first set of atmospheric ²¹⁰Po data in aerosol samples collected across Kuwait. The primary focus of this study is to investigate spatio-temporal variability of atmospheric ²¹⁰Po and assess its sources, including anthropogenic contributions. Measurements of ²¹⁰Po in aerosols collected over a period of 23 months (January 2018-November 2019) from three different locations, i.e., a remote area (120 km) north of Kuwait City, Kuwait city and an industrial site (60 km from Kuwait City center). Specific activities of ²¹⁰Po were determined in 3 different size fractions (0.39-2.5 μm, 2.5-10 μm and ≥10 μm) and the highest activity was observed in the fine fraction (PM_{0.39- 2.5}) across all sampling stations during both the summer and winter seasons. The highest activities in all the size fractions were measured downwind of the Industrial site that houses oil refineries, cement factory and some other industries including a Power and Desalination Plant. In terms of temporal variations, higher summertime activities were observed across the spatial domain. Longer residence time of atmospheric ²²²Rn-produced ²¹⁰Pb resulting in lower scavenging of atmospheric ²¹⁰Pb, due to very little precipitation in summer, will result in higher atmospheric ²¹⁰Po.

Cancer risk among career male and female Florida firefighters: Evidence from the Florida Firefighter Cancer Registry (1981-2014)

BACKGROUND

Firefighters are at increased risk for select cancers. However, many studies are limited by relatively small samples, with virtually no data on the cancer experience of female firefighters. This study examines cancer risk in over 100,000 career Florida firefighters including 5000 + females assessed over a 34-year period.

METHODS

Florida firefighter employment records (n = 109 009) were linked with Florida Cancer Data System registry data (1981-2014; ~3.3 million records), identifying 3760 male and 168 female-linked primary cancers. Gender-specific age and calendar year-adjusted odds ratios (aOR) and 95% confidence intervals for firefighters vs non-firefighters were calculated.

RESULTS

Male firefighters were at increased risk of melanoma (aOR = 1.56; 1.39-1.76), prostate (1.36; 1.27-1.46), testicular (1.66; 1.34-2.06), thyroid (2.17; 1.78-2.66) and late-stage colon cancer (1.19;1.00-1.41). Female firefighters showed significantly elevated risk of brain (2.54; 1.19-5.42) and thyroid (2.42; 1.56-3.74) cancers and an elevated risk of melanoma that approached statistical significance (1.68; 0.97-2.90). Among male firefighters there was additional evidence of increased cancer risk younger than the age of 50 vs 50 years and older for thyroid (2.55; 1.96-3.31 vs 1.69; 1.22-2.34), prostate (1.88; 1.49-2.36 vs 1.36; 1.26-1.47), testicular (1.60; 1.28-2.01 vs 1.47; 0.73-2.94), and melanoma (1.87; 1.55-2.26 vs 1.42; 1.22-1.66) cancers.

CONCLUSION

Male career firefighters in Florida are at increased risk for five cancers with typically stronger associations in those diagnosed younger than the age of 50, while there was evidence for increased thyroid and brain cancer, and possibly melanoma risk in female firefighters. Larger cohorts with adequate female representation, along with the collection of well-characterized exposure histories, are needed to more precisely examine cancer risk in this occupational group.

The sources and fate of (210)Po in the urban air: A review

The origin of (210)Po activity and its fluctuations in the air are discussed in this paper. In the case of atmospheric aerosol samples, a comparison of the (210)Po/(210)Pb and (210)Bi/(210)Pb activity ratios makes it possible not only to determine aerosol residence times but also to appraise the contribution of the unsupported (210)Po coming from other sources than (222)Rn decay, such as human industrial activities, especially coal combustion. A simple mathematical method makes it possible to observe the seasonal fluctuations of the anthropogenic excess of (210)Po in the urban air. The average doses of (210)Po intake with food (including drinking water) and inhalation of urban aerosols are usually lower than those from (210)Po intake by cigarette smokers and negligible in comparison to total natural radiation exposure.

GIS applied to location of fires detection towers in domain area of tropical forest

In most countries, the loss of biodiversity caused by the fires is worrying. In this sense, the fires detection towers are crucial for rapid identification of fire outbreaks and can also be used in environmental inspection, biodiversity monitoring, telecommunications mechanisms, telemetry and others. Currently the methodologies for allocating fire detection towers over large areas are numerous, complex and non-standardized by government supervisory agencies. Therefore, this study proposes and evaluates different methodologies to best location of points to install fire detection towers considering the topography, risk areas, conservation units and heat spots. Were used Geographic Information Systems (GIS) techniques and unaligned stratified systematic sampling for implementing and evaluating 9 methods for allocating fire detection towers. Among the methods evaluated, the C3 method was chosen, represented by 140 fire detection towers, with coverage of: a) 67% of the study area, b) 73.97% of the areas with high risk, c) 70.41% of the areas with very high risk, d) 70.42% of the conservation units and e) 84.95% of the heat spots in 2014. The proposed methodology can be adapted to areas of other countries.