An approach to comparative assessments of potential health risks from exposure to radionuclides and hazardous chemicals

The need to compare potential health risks to the public associated with different activities that can result in releases of hazardous substances to the environment is becoming increasingly important in decision-making. In making such comparisons, it is desirable to use equivalent indicators of potential health risks for radionuclides, chemical carcinogens, and noncarcinogenic hazardous chemicals. Current approaches to risk assessment that were developed for purposes of protecting human health do not provide equivalent indicators of potential risks from exposure to radionuclides and hazardous chemicals. Comparisons of environmental concentrations or calculated exposures or risks with standards for protection of public health also do not provide equivalent indicators of potential risks. We propose a simple approach to comparative risk assessments in which calculated exposures to any hazardous substances are expressed relative to no-observed-effect levels (NOELs) or, preferably, lower confidence limits of benchmark doses (BMDLs) in humans. This approach provides an equivalent, science-based indicator of the relative risks posed by different exposures to any hazardous substances.     

Never smoker lung cancer risks from exposure to particulate tobacco smoke

The average particulate environmental tobacco smoke (ETS) exposure of never and current smokers and the average lung cancer mortality rate for current smokers is estimated from empirical data. These estimates are used in a linear downward extrapolation of the lung cancer risk/mg of particulate ETS exposure for current smokers to calculate the average lung cancer risk for never smokers and the number of never smoker lung cancer deaths (LCD) in the U.S. in 1980 from exposure to particulate ETS. The estimated average daily inhaled particulate ETS exposure for never smokers is 0.62 mg/day for men and 0.28 mg/day for women. The average never smoker is estimated to retain 11% of the inhaled exposure, for a daily retained exposure of 0.07 mg for men and 0.03 mg for women. Other estimates are: a daily retained exposure for current smokers of 310 mg for men and 249 mg for women, a smoking-attributable lung cancer risk for current smokers in 1980 of 284 LCD/100,000 men and 121 LCD/100,000 women, and an annual retained-exposure lung cancer risk for never smokers of 0.64 LCD/100,000 men and 0.015 LCD/100,000 women. These risks and exposures estimate 12 lung cancer deaths among never smokers from exposure to particulate ETS: 8 among the 11.96 million male never smokers and 4 among the 28.85 million female never smokers in the U.S. in 1980. Conversely, between 655 and 3,610 never smoker lung cancer deaths are estimated from methods based on the average lung cancer risk observed in epidemiological studies of exposure to ETS. Three possible reasons for the discrepancy between the exposure and risk-based estimates are discussed: the excess risks observed in epidemiological studies are due to bias, the relationship between exposure and risk is supralinear, or sidestream tobacco smoke is substantially more carcinogenic than an equivalent exposure to mainstream smoke.     

Health risks of dietary exposure to perfluorinated compounds

Perfluorinated compounds (PFCs) form a diverse group of chemicals with surface-active properties manufactured for over 50 years. In recent years, a number of studies have reported the ubiquitous distribution of PFCs in human tissues and wildlife. Although the relative importance of the routes of human exposure to these compounds is not well established yet, it has been suggested that food intake and packaging, water, house dust, and airborne are all potentially significant sources. However, dietary intake is probably the main route of exposure to these compounds, including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), the most extensively investigated PFCs. This paper reviews the state of the science regarding the concentrations of PFCs in foodstuffs, human dietary exposure to these compounds and their health risks. The influence of processing, cooking and packaging on the PFCs levels in food is also discussed. Because of the rather limited information about human dietary exposure, studies to determine exposure to PFCs through the diet for the general population of a number of countries are clearly necessary. The correlation of PFCs body burdens and dietary intake of PFCs should be also established.     

Determination and comparison of uranium and radium isotopes activities and activity ratios in samples from some natural water sources in Morocco.

Radiochemical results (238U, 226Ra and 228Ra activities; 234U/238U, 228Ra/226Ra and 226Ra/238U activity ratios) are reported for 42 natural water samples collected from wells, hot mineral springs, rivers, tap water, lakes and irrigation water in 15 Moroccan locations. Results show that 238U activity varies between 4.5 and about 309 mBq l(-1) in wells, 0.6 and 8.5 mBq l(-1) in hot springs, 9.7 and 28 mBq l(-1) in rivers, 2.5 and 16 mBq l(-1) in tap waters and between 6 and 24 mBq l(-1) in lakes. The 234U/238U activity ratio varies in the range 0.87-3.35 in all analyzed water samples except for hot springs where it reaches values higher than 7. Unlike well water, mineral water samples present low 238U activities and high 234U/238U activity ratios and 226Ra activities. The highest activity of radium in mineral water is 150 times higher than the highest activity of 226 Ra found in well water. 226Ra/238U activity ratios are in the ranges 0.07-1.14 in wells, 0.04-0.38 in rivers, 0.04-2.48 in lakes, and 1.79-2115 in springs. The calculated equivalent doses to all the measured activities are inferior to the maximum contaminant levels recommended by the International Commission of Radioprotection and they do not present any risk for public health in Morocco.     

Health risks from large-scale water pollution: trends in Central Asia

Limited data on the pollution status of spatially extensive water systems constrain health-risk assessments at basin-scales. Using a recipient measurement approach in a terminal water body, we show that agricultural and industrial pollutants in groundwater-surface water systems of the Aral Sea Drainage Basin (covering the main part of Central Asia) yield cumulative health hazards above guideline values in downstream surface waters, due to high concentrations of copper, arsenic, nitrite, and to certain extent dichlorodiphenyltrichloroethane (DDT). Considering these high-impact contaminants, we furthermore perform trend analyses of their upstream spatial-temporal distribution, investigating dominant large-scale spreading mechanisms. The ratio between parent DDT and its degradation products showed that discharges into or depositions onto surface waters are likely to be recent or ongoing. In river water, copper concentrations peak during the spring season, after thawing and snow melt. High spatial variability of arsenic concentrations in river water could reflect its local presence in the top soil of nearby agricultural fields. Overall, groundwaters were associated with much higher health risks than surface waters. Health risks can therefore increase considerably, if the downstream population must switch to groundwater-based drinking water supplies during surface water shortage. Arid regions are generally vulnerable to this problem due to ongoing irrigation expansion and climate changes.     

Fractionation of natural radionuclides in soils from a uranium mineralized area in the south-west of Spain

A new version of a classical method was applied to study the distribution of natural radionuclides (238U, 230Th, and 226Ra) in the soil fractions obtained by a sequential extraction procedure. The potential significance of the fractions obtained with this method was tested on two very similar soils but with very different contents of the three radionuclides, collected in the proximity of a disused uranium mine located in the Extremadura region in the south-west of Spain. The results confirmed that, if only non-residual fractions are considered, the sequential method applied shows a characteristic speciation pattern of these natural radionuclides in this soil matrix, i.e., the distribution of each of the three radionuclides was very similar for the two soil samples.     

Occupational exposure to natural radioactivity in a zircon sand milling plant

Raw zirconium sand is one of the substances (naturally occurring radioactive material, NORM) which is widely used in the ceramic industry. This sand contains varying concentrations of natural radionuclides: mostly U-238 but also Th-232 and U-235, together with their daughters, and therefore may need to be regulated by Directive 96/29/EURATOM. This paper describes the method used to perform the radiological study on a zircon sand milling plant and presents the results obtained. Internal and external doses were evaluated using radioactivity readings from sand, airborne dust, intermediate materials and end products. The results on total effective dose show the need for this type of industry to be carefully controlled, since values near to 1 mSv were obtained.     

Oxidation states of uranium in depleted uranium particles from Kuwait

The oxidation states of uranium in depleted uranium (DU) particles were determined by synchrotron radiation based mu-XANES, applied to individual particles isolated from selected samples collected at different sites in Kuwait. Based on scanning electron microscopy with X-ray microanalysis prior to mu-XANES, DU particles ranging from submicrons to several hundred micrometers were observed. The median particle size depended on sources and sampling sites; small-sized particles (median 13 microm) were identified in swipes taken from the inside of DU penetrators holes in tanks and in sandy soil collected below DU penetrators, while larger particles (median 44 microm) were associated with fire in a DU ammunition storage facility. Furthermore, the (236)U/(235)U ratios obtained from accelerator mass spectrometry demonstrated that uranium in the DU particles originated from reprocessed fuel (about 10(-2) in DU from the ammunition facility, about 10(-3) for DU in swipes). Compared to well-defined standards, all investigated DU particles were oxidized. Uranium particles collected from swipes were characterized as UO(2), U(3)O(8) or a mixture of these oxidized forms, similar to that observed in DU affected areas in Kosovo. Uranium particles formed during fire in the DU ammunition facility were, however, present as oxidation state +5 and +6, with XANES spectra similar to solid uranyl standards. Environmental or health impact assessments for areas affected by DU munitions should therefore take into account the presence of respiratory UO(2), U(3)O(8) and even UO(3) particles, their corresponding weathering rates and the subsequent mobilisation of U from oxidized DU particles.     

Human exposure to environmental pollutants after a tire landfill fire in Spain: Health risks

In May 2016, a fire occurred in one of the largest landfills in Europe (Seseña, Toledo, Spain), where 70,000–90,000 tons of tires had been illegally accumulated for > 15 years. Because of the proximity of population nuclei and the duration of the episode (> 20 days), we conducted a preliminary human health risk assessment study just after the tire fire. Samples of air and soil were collected in 3 areas surrounding the landfill (El Quiñón, at only 500 m, and Seseña Nuevo and Seseña Viejo, both at 4 km), as well as in background sites. In addition, samples of crops (barley, wheat, cabbage and lettuce) were also obtained from local farmers. The concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and a number of trace elements (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Sn, Tl, and V) were analyzed in all the samples. The concentrations of all the target pollutants, excepting PAHs, were relatively similar at the different sampling zones, irrespective of the distance to the landfill. In turn, a significant increase of PAHs was noted near the tire landfill, with air levels up to 6-times higher than those found at 4 km (134 vs. 19.5–22.7 ng/m³). Similarly, PAH concentrations in lettuce were relatively higher than those typically found in monitoring programs of food safety. Because of the increase of airborne PAHs, cancer risks due to exposure to environmental pollutants for the population living at El Quiñón, near the landfill, were between 3- and 5-times higher than those estimated for the inhabitants of Seseña. After this preliminary study, further investigations, focused only on PAHs, but more extensive in terms of number of samples, should be conducted to assure that PAHs have been progressively degraded through time.     

Assessment of natural radiation exposure and radon exhalation from building materials in Greece

In controlling the natural radiation exposure for the residents of dwellings, it is necessary to determine the levels of natural radioactivity (external exposure) and radon exhalation rate (internal exposure) from building materials. Using a high-resolution gamma ray spectrometry system, the activity concentration of natural radionuclides was measured. The radon exhalation rate was measured by hermetically closing the sample in a container and following the radon activity growth as a function of time. Three different methods were applied in order to find the most appropriate, i.e. that with the less uncertainty for the less exposure time. Typical building materials were analyzed in order to examine the external and internal exposures. In addition, the total annual effective dose was evaluated for the residents of a typical Greek dwelling.     

Solid state speciation and potential bioavailability of depleted uranium particles from Kosovo and Kuwait

A combination of synchrotron radiation based X-ray microscopic techniques (μ-XRF, μ-XANES, μ-XRD) applied on single depleted uranium (DU) particles and semi-bulk leaching experiments has been employed to link the potential bioavailability of DU particles to site-specific particle characteristics. The oxidation states and crystallographic forms of U in DU particles have been determined for individual particles isolated from selected samples collected at different sites in Kosovo and Kuwait that were contaminated by DU ammunition during the 1999 Balkan conflict and the 1991 Gulf war. Furthermore, small soil or sand samples heavily contaminated with DU particles were subjected to simulated gastrointestinal fluid (0.16 M HCl) extractions. Characteristics of DU particles in Kosovo soils collected in 2000 and in Kuwait soils collected in 2002 varied significantly depending on the release scenario and to some extent on weathering conditions. Oxidized U (+6) was determined in large, fragile and bright yellow DU particles released during fire at a DU ammunition storage facility and crystalline phases such as schoepite (UO₃·2.25H₂O), dehydrated schoepite (UO₃·0.75H₂O) and metaschoepite (UO₃·2.0H₂O) were identified. As expected, these DU particles were rapidly dissolved in 0.16 M HCl (84 ± 3% extracted after 2 h) indicating a high degree of potential mobility and bioavailability. In contrast, the 2 h extraction of samples contaminated with DU particles originating either from corrosion of unspent DU penetrators or from impacted DU ammunition appeared to be much slower (20–30%) as uranium was less oxidized (+4 to +6). Crystalline phases such as UO₂, UC and metallic U or U–Ti alloy were determined in impacted DU particles from Kosovo and Kuwait, while the UO_2,34 phase, only determined in particles from Kosovo, could reflect a more corrosive environment. Although the results are based on a limited number of DU particles, they indicate that the structure and extractability of DU particles released from similar sources (metallic U penetrators) will depend on the release scenarios (fire, impact) and to some extent environmental conditions. However, most of the DU particles (73–96%) in all investigated samples were dissolved in 0.16 M HCl after one week indicating that a majority of the DU material is bioaccessible.     

Comparison of different methods for uranium determination in water

Photometry, laser photometry, liquid scintillation (LSC), gamma spectrometry and alpha spectrometry were used for estimating waterborne uranium concentration. The chemical procedures applied were pre-concentration, liquid extraction, chromatographic resin extraction and precipitation. Our results show that laser photometry is an easy and accurate method capable of estimating low uranium concentrations, parts of micrograms per litre. It is not applicable for higher concentrations, difficult water matrixes and isotope determination. The classical photometry is complementary, resolving the problem related to high concentrations, practically up to 10 mg/l. Alpha and gamma spectrometry resolve the problem of precise isotope determination, but with the disadvantage of hard chemical preparation and long measurement times. An intermediate method is LSC, with the problem of isotope estimation, due to poor energy resolution.     

The removal of uranium from mining waste water using algal/microbial biomass

We describe a three step process for the removal of uranium (U) from dilute waste waters. Step one involves the sequestration of U on, in, and around aquatic plants such as algae. Cell wall ligands efficiently remove U(VI) from waste water. Growing algae continuously renew the cellular surface area. Step 2 is the removal of U-algal particulates from the water column to the sediments. Step 3 involves reducing U(VI) to U(IV) and transforming the ions into stable precipitates in the sediments. The algal cells provide organic carbon and other nutrients to heterotrophic microbial consortia to maintain the low E(H), within which the U is transformed. Among the microorganisms, algae are of predominant interest for the ecological engineer because of their ability to sequester U and because some algae can live under many extreme environments, often in abundance. Algae grow in a wide spectrum of water qualities, from alkaline environments (Chara, Nitella) to acidic mine drainage waste waters (Mougeotia, Ulothrix). If they could be induced to grow in waste waters, they would provide a simple, long-term means to remove U and other radionuclides from U mining effluents. This paper reviews the literature on algal and microbial adsorption, reduction, and transformation of U in waste streams, wetlands, lakes and oceans.     

Determination of uranium and radon in potable water samples

In this work, potable water samples collected from boreholes of the Migdonia valley, located NE of the city of Thessaloniki, were analyzed for the determination of uranium (238U) and radon (222Rn) concentrations. The objective of the present work is to examine if there is any correlation between radon and uranium concentrations in the water samples. For the determination of traces of uranium in water samples, an analytical technique was developed based on the selective adsorption of uranium on the chelating resin, SRAFION NMRR, and the in situ determination of the retained uranium by instrumental neutron activation analysis (INAA). By the described procedure, it was possible to determine uranium amounts in the range of microg/l. For measuring radon in water, a liquid scintillation counting system, using the Packard protocol was employed. The measured 222Rn activity concentrations are from background level up to 160 Bq l (-1).     

Assessing and managing the risks of accidental releases of hazardous gas: A case study of natural gas wells contaminated with hydrogen sulfide

Natural gas wells contaminated with the toxic gas hydrogen sulfide (i.e., sour-gas wells) pose potential health risks to workers and to nearby residents. The health risks are a function of the dose-response relationship of hydrogen sulfide, the likelihood of accidental releases, gaseous emission rates, the nature of releases at the well head, dispersion of the emitted gas, and the characteristics of the population at risk. We discuss each of these factors and present a risk analysis of a hypothetical sour-gas well in the vicinity of Evanston, WY. We found that the greatest risks for life-threatening effects would occur in the northwest downwind sector after a horizontal release of gas at the well. Subacute effects (e.g., respiratory irritation) after a vertical release of gas would occur primarily to the northeast. Management of health risks involves the use of techniques for preventing inadvertent releases and methods for limiting population exposures.     

Genomic instability in human osteoblast cells after exposure to depleted uranium: delayed lethality and micronuclei formation

It is known that radiation can induce a transmissible persistent destabilization of the genome. We have established an in vitro cellular model using HOS cells to investigate whether genomic instability plays a role in depleted uranium (DU)-induced effects. Transmissible genomic instability, manifested in the progeny of cells exposed to ionizing radiation, has been characterized by de novo chromosomal aberrations, gene mutations, and an enhanced death rate. Cell lethality and micronuclei formation were measured at various times after exposure to DU, Ni, or gamma radiation. Following a prompt, concentration-dependent acute response for both endpoints, there was de novo genomic instability in progeny cells. Delayed reproductive death was observed for many generations (36 days, 30 population doublings) following exposure to DU, Ni, or gamma radiation. While DU stimulated delayed production of micronuclei up to 36 days after exposure, levels in cells exposed to gamma-radiation or Ni returned to normal after 12 days. There was also a persistent increase in micronuclei in all clones isolated from cells that had been exposed to nontoxic concentrations of DU. While clones isolated from gamma-irradiated cells (at doses equitoxic to metal exposure) generally demonstrated an increase in micronuclei, most clonal progeny of Ni-exposed cells did not. These studies demonstrate that DU exposure in vitro results in genomic instability manifested as delayed reproductive death and micronuclei formation.     

Bioaccumulation and biological effects in the earthworm Eisenia fetida exposed to natural and depleted uranium

The accumulations of both natural (U) and depleted (DU) uranium in the earthworms (Eisenia fetida) were studied to evaluate corresponding biological effects. Concentrations of metals in the experimental soil ranged from 1.86 to 600 mg kg⁻¹. Five biological endpoints: mortality, animals’ weight increasing, lysosomal membrane stability by measuring the neutral red retention time (the NRRT), histological changes and genetic effects (Comet assay) were used to evaluate biological effects in the earthworms after 7 and 28 days of exposure. No effects have been observed in terms of mortality or weight reduction. Cytotoxic and genetic effects were identified at quite low U concentrations. For some of these endpoints, in particular for genetic effects, the dose (U concentration)-effect relationships have been found to be non-linear. The results have also shown a statistically significant higher level of impact on the earthworms exposed to natural U compared to depleted U.     

Population exposure to airborne thorium at the high natural radiation areas in India

High natural radiation areas in the coastal and peninsular India were studied for airborne thorium and resultant population exposure due to inhalation. Four locations covering three states viz., Ayiramthengu and Neendakara in Kerala, Kudiraimozhi in Tamil Nadu and Bhimilipatnam in Andhra Pradesh were investigated. External gamma radiation fields 1 m above the monazite ore bodies ranged from 200 to 3000 nGy h^-1. Soil samples showed ²³²Th specific activity varying from 0·1 to 1·5 Bq g^-1 with surface alpha activity in the range of 1·0–12·5 Bq cm^-2. Suspended particulates in the samples ranged from 60–140 μg m^-3 with ²³²Th showing a wider variation of <0·03–0·3 mBq m^-3. There was poor correlation between suspended particulates and long-lived alpha airborne activity . The resuspension factors for ²³²Th were in the range of 1·5×10^-8–7·9×10^-7 cm^-1. Higher resuspension was correlated with dry sand dunes. The upper limits for Committed Effective Dose (CED) due to inhalation of airborne ²³²Th at the respective high natural radiation areas were estimated to range from 50±30 to 300±130 μSv (5–30 mrem) per year per adult member of public assuming an activity median aerodynamic diameter of 1 μm for the airborne particulates.     

Arbuscular mycorrhizas contribute to phytostabilization of uranium in uranium mining tailings

Uranium (U) tailings pose environmental risks and call for proper remediation. In this paper medic and ryegrass plants were used as host plants to examine whether inoculation with an AM fungus, Glomus intraradices, would help phytostabilization of U tailings. The need of amending with uncontaminated soil for supporting plant survival was also examined by mixing soil with U tailing at different mixing ratios. Soil amendment increased plant growth and P uptake. Ryegrass produced a more extensive root system and a greater biomass than medic plants at all mixing ratios. Medic roots were extensively colonized by G. intraradices whereas ryegrass were more sparsely colonized. Plant growth was not improved by mycorrhizas, which, however, improved P nutrition of medic plants. Medic plants contained higher U concentrations and showed higher specific U uptake efficiency compared to ryegrass. In the presence of U tailing, most U had been retained in plant roots, and this distribution pattern was further enhanced by mycorrhizal colonization. The results suggest a role for AM fungi in phytostabilization of U tailings.