Average Excess Lifetime Cancer Risk Research Articles

Measurement of Background Ionizing Radiation Around Beta Glass Plc and Its Environs, Ughelli, Delta State, Nigeria

A study of the background ionizing radiation levels to helps monitor the impact of human activities on the environment, such as mining, farming, glass bottle production and power generation has been carried out around Beta glass Plc and Transcorp Power LTD using a hand-held gamma spectrometer (GAMMA-SCOUT; Geiger counter Radiation meter) and GPS (Oregon-450 Garmin). The study of the BIR levels was carried out between June to July, 2022. The average measured exposure rates (AV. BIR) ranged from 0.007 mRh-1 to 0.013 mRh-1, with 0.010±0.0002 mRh-1 as the average. The estimated mean outdoor absorbed dose rate (ADR) for the study region was 113.10 Gyh-1 to 87.153±2.091 Gyh-1, with an average annual effective dose equivalent (AEDE) of 106.884±2.565 mSvy-1 and an average excess lifetime cancer risk (ELCR) of (0.374±0.009) × 10-3. The measured values of radiological parameters, such as annual dose rate, annual effective dose rate, and excess lifetime cancer, were higher than background radiation levels. The average BIR is in line with the ICRP recommendation of 0.013 (mRh-1), while the effective dose rate (EDR) is somewhat below the ICRP recommendation of 1.00 (mSvy-1) for a normal environment. The obtained values of the radiological indicators, such as ADR, AEDE, and ELCR, are greater than the background radiation norm of 59 (?Gyh-1), 0. 07 (mSvy-1), and 0.29×10-3. The study found that radiation levels and doses in the study location do not immediately harm personnel or residents, but increased lifetime cancer risk values suggest that cumulative dosages may cause cancer.

Radiological landscape of natural resources and mining: Unveiling the environmental impact of naturally occurring radioactive materials in Ghana's mining areas

This study provides a general observation of the status of naturally occurring radioactive materials (NORMs) distribution in mining and industrial areas of Ghana in order to establish regional and national data on NORMs. The study includes data on radioactivity concentrations of U-238, Th-232, and K-40 in soils and for water concentrations of Ra-226, Th-228, and K-40 from various mining, oil, and gas communities, as well as water sources used for crop farming and farmlands. The average activity concentrations of U-238, Th-232, and K-40 in the soil samples were found to be 59 ± 16 Bq/kg, 48 ± 15 Bq/kg, and 286 ± 57 Bq/kg, respectively. The average concentration of Ra-226, Th-228, and K-40 in the water samples were found to be 1.62 ± 0.33 Bq/L, 2.08 ± 0.53 Bq/L, and 22.36 ± 3.44 Bq/L, respectively. The estimated average annual effective doses from external and internal exposure pathways in soil and water samples were 0.09 mSv/y and 0.54 mSv/y, respectively. The total annual effective dose resulting from both exposure pathways was calculated to be 0.63 mSv/y, which is below the 1 mSv/y dose limit recommended by the International Commission on Radiological Protection (ICRP) for controlling public radiation exposure. Based on the radiological hazard indices, the majority of the soil samples were found to be suitable as building materials as their respective indices were below the limits except for two sample locations and the sludge and scale samples. The average Excess Lifetime Cancer Risk (ELCR) value of the water samples was 1.6 times greater than the recommended value of 1.16 × 10−3, presenting a relatively higher risk to the public of developing cancer. No significant regional differences in the levels of radioactive elements. The regression models demonstrate strong interrelationships between the studied elements, with high R-squared values suggesting a predictable nature of one element’s concentration based on others.

Occupational lead exposure health risk assessment and heme biosynthesis: A study on batik artisans in yogyakarta, Indonesia

This study aims to assess dermal and inhalation lead exposure levels among batik industry workers and evaluate noncarcinogenic and carcinogenic health risks associated with lead exposure. We investigate potential relationships between lead exposure (dermal average daily dose and inhalation exposure concentration) and the workers' blood hemoglobin levels (Hb), as well as their urinary ALA (u-ALA) concentrations. Additionally, we explore any possible associations between Hb and u-ALA levels among the workers and identify various factors influencing lead exposure levels. A total of 30 workers were recruited for the study. Interviews and exposure sampling were conducted to measure dermal and inhaled lead exposure. Sample analysis methods include XRF for exposure samples, spectrophotometry for u-ALA, and HiCN colorimetric for Hb. Carcinogenic and noncarcinogenic risk assessments, correlation analysis, as well as ANOVA for factors analysis, were performed. The average dermal exposure dose and inhalation exposure concentration of lead were 6.53 ± 3.2 ng/kg/day and 0.021 ± 0.015 μg/m3, respectively. Hazard Index (HI) values for all workers were below 1 (average: 0.372 ± 0.155), indicating no expected noncarcinogenic health effects due to lead exposure. The average Excess Lifetime Cancer Risk (ELCR) was (5.18 ± 3.84) × 10−8, significantly below acceptable limits. Correlation analysis revealed a significant negative correlation between Hb and u-ALA (r = −0.519, p = 0.058 for male workers and r = −0.531, p = 0.034 for female workers), supporting their use as lead exposure biomarkers. The factors analysis demonstrated a significant impact of working conditions on inhalation exposure (p = 0.018), with outdoor workers experiencing lower lead inhalation. This research provides crucial insights into potential dangers faced by batik workers due to lead exposure, emphasizing the importance of targeted interventions. The strong correlation between Hb and u-ALA indicates their combined effectiveness in detecting lead exposure, even at low levels. The study underscores the significance of outdoor work as a protective measure against inhaling heavy metals, such as lead, present in the air. The assessment of health risks associated with lead exposure in the batik industry lays the groundwork for informed decision-making and interventions to protect workers' well-being, particularly in informal sectors workplaces where health risks are often overlooked.

ASSESSMENT OF INDOOR AND OUTDOOR RADIATION DOSE LEVELS IN DELTA STATE POLYTECHNIC, OGWASHI-UKU, DELTA STATE, NIGERIA

This study assessed the indoor and outdoor radiation dose levels of twelve (12) laboratories of Delta State Polytechnic, Ogwashi-Uku using a handheld inspector survey meter and estimation revealed that the average BIR, average annual equivalent dose rate (EDR), average annual absorbed dose rate (ADR), average annual effective dose equivalent (AEDE), average excess lifetime cancer risk (ELCR) is 0.0116 mR/hr, 0.9733 mSv/yr, 100.69 nGy/hr, 0.4940 mSv/yr and 1.755. Dose to organs showed that the testes received the highest dose, while the liver received the lowest dose indoors and outdoors respectively. In general, indoor and outdoor BIR, ED, AD, and AEDE values ​​are less than the recommended limit of unity (1 mSv/yr) for public exposure (ICRP). ELCR for indoor and outdoor is above the world permissible limit of 0.29×10-3. The calculated ELCR in the study area is 1:29719 (about 33 in 1 million) indoors and 1:115735 (9 in 1 million) outdoors. Although the average value for ELCR in this study is high further analysis and studies need to be carried out to ascertain the risk of staff and students to cancer.

Measurement of Activity Concentration of 40K, 226Ra and 232Th in Commercial Wall Paints Used in Nigeria and Inherent Radiological Hazards

Ionizing radiations from building materials portend serious health risk to atoms and molecules of body cells by damaging tissues and altering the DNA in genes. In this study, the measurement of radioactivity concentration of 40K, 226Ra and 232Th to determine inherent radiological hazards in major brands of commercial wall paints used in Nigeria was carried out. Twenty paint samples were selected based on the popularity and quantity of sales of these paints’ brands as obtained from oral interview with these paints’ marketers. A NaI (Tl) detector (76×76 mm) was employed in the measurements. High mean levels of the radioactivity of 40K, 226Ra and 232Th were observed in emulsion paints 174.73, 58.18 and 56.98 Bq/kg while oil paints gave lower values of 119.66, 44.66 and 37.86 Bq/kg for 40K, 226Ra and 232Th respectively. From results obtained, most of the emulsion and oil paints available in Nigeria present low level of radioactivity concentration which does not pose significant radiological risk to user population. However, average excess lifetime cancer risk of these paints gave a value higher than the recommended limit. Based on this, regulation, quality control and constant monitoring of raw materials used for paint production in Nigeria is highly advised.

Determination of 40K, 226Ra and 228Ra concentrations with dose rates in crayfish from Ode Omi River and radiological implications to the consumers

Natural radionuclides such as 40K, 226Ra and 228Ra are found naturally in water and sediments of rivers, likewise in soils. They are transferred to aquatic animals through ingestion. Radioactivity concentrations and dose rates of 40K, 226Ra and 228Ra in crayfish species from Ode Omi River in coastal region, Ogun State Southwest of Nigeria were determined by gamma spectrometry using NaI (TI) detector coupled with a pre-amplifier base to a multiple channel analyzer (MCA). 15 samples of crayfish were collected. Cherax tenuimanus had the highest mean concentration and dose rate of values 106.87 ± 9.11 Bq kg–1 and 0.00960 mGy hr–1 respectively for 40K. Moreso, for 226Ra, Cherax quadricarinatus had the highest mean concentration and dose rate of values 2.57 ± 0.82 Bq kg–1 and 4.50 x 10–7 mGy hr–1 respectively. Concerning228Ra, Astacopsis gouldi had the highest mean concentration and dose rate of values 5.23 ± 0.46 Bq kg–1 and 5.86 x 10–13 mGy hr–1, respectively. The average dose rate of the radionuclides in all the crayfish was calculated to be 4.62 x 10 ̶ 3 mGy hr–1 which was below the 0.4 mGy hr–1 limit recommended. The average annual committed effective dose and average excess lifetime cancer risk of all the radionuclides to the consumers were 0.0807 mSv yr–1 and 0.589 x 10–4, respectively, which were below global limits of 1.0 mSv yr–1 and 0.29 x 10–3, respectively, therefore, the ingestion of these natural radionuclides could not pose any radiological health hazards to the aquatic animals, likewise man the consumers.
 Keywords: Radionuclide concentration, Dose rate, Cancer Risk.

Assessment of ionizing radiation exposure levels and associated health risk in some selected solid mineral mining sites Edo-North, Nigeria

Ionizing radiation exposure rate and its associated health risks were assessed using Digilert 200 and Rados Radiation Monitoring Meter, integrated with Geographical Positioning System (Garmin GPSMAP 76S) of some selected solid mineral mining sites across Edo-North Nigeria. The mean exposure rates show some characteristic range of 0.010±0.005 𝑚𝑅ℎ𝑟−1 to 0.027 𝑚𝑅ℎ𝑟 −1 across the entire study. The obtained mean exposures rates at all the mining pits were higher than the ICRP standard limit of 0.013 𝑚𝑅ℎ𝑟 −1 , except at freedom limestonesmining pit where we recorded 0.010 mRh-1. It was also observed that limestones mining sites exhibited low exposure rate while granite mining sites exhibited high exposure rate. The computed equivalent dose rate ranges from 1.049 mSvy-1 to 2.287 mSvy-1 , which is well above the recommended permissible limit of 1.0 mSvy-1 for the general public. 91.7% of the mining sites recorded higher absorbed dose rate but the mean AEDE recorded across the entire study area are below the ICRP standard. The average excess lifetime cancer risk shows variation from 0.472 x 10-3 to 1.27 x 10-3 . . By this result, the probability of contacting cancer due to radiation exposure is higher in places like Cinoma pit, Cetraco pit, Niger-Cat pit, Jigom pit, Oaries pit and Petra-Quarries pit.
 Keywords: Assessment, Mining pits, Background, Exposure, lifetime cancer risk

Annual Committed Effective Doses of Primordial Radionuclides and Excess Lifetime Cancer Risk to the Consumers of Some Foodstuffs in Lagos, Southwest of Nigeria

Food plays vital role in the survival of man as it provides necessary nutrients to the body in orderto carry out the daily activities and also to be in good health. Activity concentrations of 40K,238Uand 232Th in some foodstuffs from three highly rated markets in Lagos, Southwest of Nigeriahave been determined by gamma spectrometry method using NaI (TI) detector coupled with a preamplifierbase to a multiple channel analyzer (MCA). Fifteen (15) samples of maize flour, yamflour, beans, cassava flour and rice were randomly purchased from the markets: Ketu, Oyingboand Ikeja. The highest activity concentrations for 40K, 238U and 232Th were 153.47 ± 10.34 Bqkg−1, 9.26 ± 2.17 Bq kg−1 and 15.36 ± 4.05 Bq kg−1, respectively, all from yam flour. The meanconcentrations of 40K for all the samples were obtained to be 102.33 ± 7.04 Bq kg−1, 5.79 ± 1.35Bq kg˗1 for 238U and 9.15 ± 2.36 Bq kg−1 for 232Th. The average annual committed effective doseof all the natural radionuclides to the consumers of the foodstuffs was determined to be 0.144 mSvyr−1 and average excess lifetime cancer risk to the consumers was determined to be 0.503 x 104.The values obtained were below the worldwide limits of 1 mSv yr−1 and 0.29 x 10−3,respectively, which indicated that consumption of the foodstuffs had no significant negativeradiological health risks to the consumers.
 Keywords: Radionuclide; Activity concentration; Foodstuff; Dose; Gamma spectrometry;

Assessment of natural radioactivity and consequent radiological hazard in different brands of commercialized bottled mineral water produced in China.

As one of the drinking water quality parameters, natural radioactivity parameters are recommended to prevent a potential health threat to the public. In this study, the gross-α and gross-β activity concentrations in 15 different brands of commercial bottled mineral water consumed in China were analyzed to evaluate the quality and corresponding health impact on the population. The activity concentrations of gross-α and gross-β in different samples varied from 4.4 to 130.6 and 17.3-320.3 mBq L-1, respectively. The values of the annual effective dose equivalent rate (AED) for infants, children and adults ranged from 1.3 to 21.6, 2.9-52.5 and 5.5-97.8 μSv y-1, respectively. The average excess lifetime cancer risk caused by the consumption of bottled mineral water samples was estimated as 6.0 × 10-5. These results show that all the measured gross-α and gross-β are found to be obviously less than the guidance level by WHO and the domestic standard. The values of AED are below the World Health Organization (WHO) recommended limit of 0.1 mSv y-1. Combined with the lifetime cancer risk assessment, it is concluded that there is no significant risk for consumption of the observed brands of bottled mineral water and it can be consumed safely.

Evaluation of Primordial Radionuclides in <I>Ocimum gratissimum</I> and health Risk to the Consumers at Ewekoro Southwest of Nigeria

Primordial radionuclides are transported in to the plants through the leaves and roots. Medicinal plants are widely used in Africa for prevention and treatment of diseases. Ocimum Gratissimum is medicinal plant that is so used in southwest of Nigeria due to its multifunctional traditional medicinal health uses and as spice in cooking. The research is to determine the radiological health risk of these primordial radionuclides to the consumers of Ocimum Gratissimum in the study area. Fresh leaves of the medicinal plant were plucked from ten (10) different locations at Ewekoro where mining of limestone had been taking place in Ogun State, southwest of Nigeria, been the part of the plant that was commonly used. The concentrations of 40K, 238U and 232Th in the fresh leaves were determined using gamma spectrometry method, and average annual committed effective dose to the adult consumers was determined. No artificial radionuclide was detected. The highest annual committed effective doses of 40K, 238U and 232Th to the consumers of Ocimum Gratissimum were obtained to be 0.00133mSvy-1, 0.00147mSvy-1 and 0.00336mSvy-1 respectively. The highest excess lifetime cancer risk of 40K, 238U and 232Th to the consumers were calculated to be 0.0211 x 10-3, 0.0136 x 10-3 and 0.1434 x 10-3 respectively. The average annual committed effective dose and average excess lifetime cancer risk of the radionuclides to the consumers were calculated to be 0.0109mSvy-1 and 0.0379 x 10-3 respectively. The values were below the limits of 0.3mSvy-1 and 0.29 x 10-3 respectively, recommended globally. The consumers of the medicinal plant do not have significant radiological health risk. Furthermore, the results obtained can serve as reference data for future studies in the study area and its environs.
 Keywords: Primordial Radionuclide, Medicinal plant, Dose, Cancer

Artisanal Gold Mining Activity in Northcentral Nigeria and Its Implications: Radiological Approach

Artisanal gold mining is one of the anthropogenic activities identified by the United Nations Scientific Committee on the Effects of Atomic Radiation as potential source of exposure to naturally occurring radionuclides. 40 surface soil samples collected at random from Gababiyu artisanal gold mining site in Minna Metropolis were assessed for their natural radioactivity using gamma spectrometric technique which employs NaI (Tl) gamma-ray detector. Specific activities of 226Ra, 232Th and 40K in the soil varied from 10.27±2.88 to 152.60±3.80, 32.67±1.93 to 185.90±6.06 and 35.18±1.45 to 947.50±7.51 Bq kg-1 respectively, with mean values of 65.06±4.20, 87.63±2.89 and 267.94±4.29 Bq kg-1 in sequence. Although 226Ra and 232Th recorded activity values slightly above world average, they are still within safety range prescribed by UNSCEAR. Computed average absorbed dose rate at 1 m above ground was 94.16 nGy h-1 with corresponding mean annual dose equivalent of 0.12 mSv.y-1. Furthermore, calculated average excess lifetime cancer risk was found to be 0.40×10-3, which is slightly above the UNSCEAR safety limit. Pearson correlation statistics identified 226Ra and 232Th as principal radionuclides responsible for the computed radiation risk variables. Although the results of this investigation does not show any immediate radiological risk, continuous monitoring of the gold mining site is encouraged in order to keep the radiation effects as low as reasonably achievable.

Estimation of cancer risk due to radiation exposure for some daily consumption of foods.

Considering the increasing concern about the cancer risk caused by environmental radiological effects related to the food consumption, the study was carried out evaluate the activity concentrations and cancer risk assessments of 226 Ra,232 Th, and 40 K in 72 food samples collected from different suppliers in Tehran Province of Iran. The specific activity concentration was determined by means of a high-resolution high-purity germanium gamma-spectroscopy system. The collected various sample groups were wheat, rice, meat, milk, and mushroom. The maximum concentration of 226 Ra and 232 Th was found in the wheat sample, equal to 0.7862 Bq/kg and 0.968 Bq/kg, respectively, whereas for 40 K, it was 598.35 Bq/kg in the milk sample. The annual effective dose rate ranged from 2.47 μSv/y in mushroom to 64.66 μSv/y in rice. The average excess lifetime cancer risk (ELCR) was varied from 1.60 × 10-5 for mushroom to 4.20 × 10-4 for milk, with the total ELCR value from main daily diets 1.37 × 10-3, which was a little more than the acceptable ELCR limit of 10-3. The ELCR due to five main daily diets was a little more than the acceptable ELCR limit of 10-3 for radiological risk in general.

Natural radioactivity in soils around mega coal-fired cement factory in Nigeria and its implications on human health and environment

Cement industry is one of the anthropogenic activities capable of mobilizing and propagating naturally occurring radioactive materials (NORM) in human environment to levels that may become detrimental to human health. A pilot survey of radiological implications of a mega cement factory (AshakaCem), north-eastern Nigeria, on human health and the environment was conducted using high-purity germanium (HPGe) gamma-ray spectrometric technique. Average activity concentrations for 226Ra, 232Th and 40K in the soil samples were found to be 7.41 ± 0.44, 16.27 ± 0.84 and 196.11 ± 9.08 Bq kg−1, respectively. These values were lower than the world mean values documented by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Calculated radiation hazard parameters associated with the studied soil samples showed mean air absorbed dose rate of 21.43 nGy h−1, with attendant annual effective dose of 0.03 mSv y−1 and average excess lifetime cancer risk of 0.9 × 10−4. Statistical analysis revealed strong relationship between calculated hazard parameters and the investigated natural radionuclides in the studied soil samples and confirmed that 226Ra, 232Th and 40K were major contributors to radiation dose. Results obtained from this study fall within acceptable limits provided for human safety and environmental protection. Thus, the operations of AshakaCem did not provide any significant radiological risk to workers nor pose any immediate radiological threat to the environment.

Outdoor radioactivity and health risk assessment for capital city Ankara, Turkey

The aim of this study is to determine the soil radioactivity levels and assess the possible relevant health hazards for the inhabitants of Ankara province. Total of 341 samples were collected from predetermined locations and outdoor gamma dose rate measurements were carried out. The mean activity of 40K, 226Ra, 232Th, and 137Cs with the ranges were determined as 454 (23–1355), 27 (6–186), 33 (2–181) and 3.3 (0.5–20.9) Bq kg−1, respectively. The average annual effective dose equivalent was found to be 71.8 µSv y−1 for public exposure and the average excess lifetime cancer risk value was calculated as 2.69E−04.

Radiological Impacts of Natural Radioactivity in Locally Produced Tobacco Products in Ibadan, Oyo State, Nigeria

Radionuclides are found naturally in air, water and soil. They are even found in vegetation, consumer products and in human body. Everyone on the planet is exposed to some background level of ionizing radiation through external exposures that occurs as a result of irradiation, and internal exposures that occurs as a result of ingestion and inhalation. Studies have shown that tobacco contains minute quantities of radioisotopes from uranium and thorium-decay series which are radioactive and carcinogenic. Tobacco product increases both external and internal exposure due to these radioisotopes. In fact, tobacco products have been considered to be one of the most significant causes of lung cancer. Owing to the large-scale consumption of tobacco in Nigeria at the present time, locally produced tobacco products in Nigeria were collected from the market and the naturally-occurring 238U and 232Th decay series, as well as non-series decay 40K in these products were measured using γ-ray spectrometer. The radiological impacts of the radionuclides in these products were assessed from their specific activities. The average values of the absorbed dose rate were 19.72 and 17.59 nGy h -1 for snuff and cigarette products respectively. The average values of the effective doses due to daily inhalation of smoke by consumers from one wrap of snuff and one stick of cigarette products is 592.32 and 66.62 μSv yr -1 respectively. Similarly, the values of the radium equivalent activity index for snuff and cigarette samples were 40.95 and 38.95 Bq kg -1 respectively. Also the external radiation hazard index were 0.12 and 0.11 for snuff and cigarette samples respectively while the internal radiation hazard index were 0.17 and 0.15 for the two samples respectively. The average excess lifetime cancer risk (x 10 -3 ) values for daily inhalation of smoke from one wrap of snuff and one (1) stick of cigarette were 2.07 and 0.23 x 10 -3 respectively. The estimated values of some of these parameters were found to be lower than the recommended limit by UNSCEAR (2000). However, the effective dose poses a serious health risk to addicted consumers of the product when three (3) or more wraps of snuff and one (1) or more packs of cigarette products are consumed daily. The mean excess lifetime cancer risks values estimated were also much higher than the recommended limits by UNSCEAR (2000). This then makes the risk of suffering cancer and other radiation injuries to be high. Keywords : Radiological impacts, Tobacco, Cigarette, Snuff, Cancer, Radiation injury, Nigeria.

Radiological Impacts of Natural Radioactivity in Locally Produced Tobacco Products in Oyo State, Nigeria

Radionuclides are found naturally in air, water and soil. They are even found in vegetation, consumer products and in human body. Everyone on the planet is exposed to some background level of ionizing radiation through external exposures that occurs as a result of irradiation, and internal exposures that occurs as a result of ingestion and inhalation. Studies have shown that tobacco contains minute quantities of radioisotopes from uranium and thorium-decay series which are radioactive and carcinogenic. Tobacco product increases both external and internal exposure due to these radioisotopes. In fact, tobacco products have been considered to be one of the most significant causes of lung cancer. Owing to the large-scale consumption of tobacco in Nigeria at the present time, locally produced tobacco products in Nigeria were collected from the market and the naturally-occurring 238U and 232Th decay series, as well as non-series decay 40K in these products were measured using γ-ray spectrometer. The radiological impacts of the radionuclides in these products were assessed from their specific activities. The average values of the absorbed dose rate were 19.72 and 17.59 nGy h-1 for snuff and cigarette products respectively. The average values of the effective doses due to daily inhalation of smoke by consumers from one (1) stick of cigarette and one (1) wrap of snuff products were 66.62 and 592.32 μSv yr-1 respectively. Similarly, the values of the radium equivalent activity index for snuff and cigarette samples were 40.95 and 38.95 Bq kg-1 respectively. Also, the external radiation hazard index was 0.12 and 0.11 for snuff and cigarette samples respectively while the internal radiation hazard index was 0.17 and 0.15 for the two samples respectively. The average excess lifetime cancer risk (× 10-3) values for daily inhalation of smoke from one (1) stick of cigarette and one (1) wrap of snuff were 0.23 and 2.07 × 10-3 respectively. The estimated values of some of these parameters were found to be lower than the recommended limit by UNSCEAR (2000). However, the effective dose poses a serious health risk to addicted consumers of the product and passive smokers in the environment when three (3) or more wraps of snuff and one (1) or more packs of cigarette products are consumed daily. The mean excess lifetime cancer risks values estimated were also much higher than the recommended limits by UNSCEAR (2000). This then makes the risk of suffering cancer and other radiation injuries to be high.

Long-term trends (1990–2014), health risks, and sources of atmospheric polycyclic aromatic hydrocarbons (PAHs) in the U.S.

Polycyclic aromatic hydrocarbons (PAHs) are a category of over 100 various chemicals released from numerous combustion sources. The ubiquity and toxicity of PAHs have posed high health risks on human populations. This study aims to examine the long-term trends of atmospheric PAHs at the national-level in the U.S., and evaluate their cancer risks. Daily concentrations of PAHs measured at 169 monitoring stations between 1990 and 2014 were obtained from the U.S. Environmental Protection Agency's Air Quality System. Temporal trends were examined using generalized linear model with generalized estimating equations. Random-effects analysis of variance was performed to explore variance between regions, sites, years, and months with a hierarchical structure. Source categories were identified using diagnostic ratios. National population level cancer risks were estimated using the relative potency factors and inhalation unit risk method. Ambient PAH concentrations displayed an overall downward trend (6–9% annual reduction) in urban areas, but not in rural areas. Seasonal and weekday/weekend effects were significant. Urban concentrations were twice of the rural level. The between-site variation outweighed the temporal variation, indicating large spatial heterogeneity. The predominant PAH sources were from traffic and non-traffic related fuel combustions with a dominant contribution from diesel emissions. The average excess lifetime cancer risk was estimated to be 9.3 ± 30.1 × 10−6 (GM: 4.2 × 10−6) from exposure to ten carcinogenic PAHs. This is the first comprehensive study of the spatiotemporal trends of ambient PAHs at the U.S. national level. The results indicate that future efforts aimed to reduce PAH exposures should focus on diesel emission controls and extending the geographic coverage of air monitoring.

Quantification and Radiological Risk Estimation Due to the Presence of Natural Radionuclides in Maiganga Coal, Nigeria.

Following the increasing demand of coal for power generation, activity concentrations of primordial radionuclides were determined in Nigerian coal using the gamma spectrometric technique with the aim of evaluating the radiological implications of coal utilization and exploitation in the country. Mean activity concentrations of 226Ra, 232Th, and 40K were 8.18±0.3, 6.97±0.3, and 27.38±0.8 Bq kg-1, respectively. These values were compared with those of similar studies reported in literature. The mean estimated radium equivalent activity was 20.26 Bq kg-1 with corresponding average external hazard index of 0.05. Internal hazard index and representative gamma index recorded mean values of 0.08 and 0.14, respectively. These values were lower than their respective precautionary limits set by UNSCEAR. Average excess lifetime cancer risk was calculated to be 0.04×10−3, which was insignificant compared with 0.05 prescribed by ICRP for low level radiation. Pearson correlation matrix showed significant positive relationship between 226Ra and 232Th, and with other estimated hazard parameters. Cumulative mean occupational dose received by coal workers via the three exposure routes was 7.69 ×10−3 mSv y-1, with inhalation pathway accounting for about 98%. All radiological hazard indices evaluated showed values within limits of safety. There is, therefore, no likelihood of any immediate radiological health hazards to coal workers, final users, and the environment from the exploitation and utilization of Maiganga coal.

Cancer Risk due to Radionuclides Concentration in Tin Ores and Sediments at Barkin-Ladi, Plateau State, North Central, Nigeria

The specific activity concentrations of natural radionuclides 40K, 226Ra and 232Th in soil samples of abandoned tin ore and sediment from tin mining areas in Barkin-ladi were measured by gamma-ray spectrometry system using Sodium Iodide [NaI(Tl)] detector. Radiological hazard assessments due to these natural radionuclides were carried out. The aim was to assess the associated lifetime cancer risk owing to inhalation of the short life Radon gas from the tin ore and sediments by the inhabitants of this area after 70 years of exposure. The calculated activity concentrations of 40K, 226Ra and 232Th in the collected ore samples were 275.44 ± 46.14, 239.95 ± 30.82 and 778.78 ± 29.30 Bqkg-1 respectively while those of the sediment samples were 1608.25 ± 55.60, 759.62 ± 47.95 and 4861.82 ±48.78 Bqkg-1 respectively. However, the mean absorbed dose rate in ores (629.86 nGyh-1) and in sediments (3612.05 nGyh-1), the mean radium equivalent in ores (1374Bqkg-1) and in sediments (7835.88 Bqkg-1) and the mean annual effective dose rate in ores (0.77mSvy-1) and in sediments (4.43mSvy-1) were all found to be higher than the recommended global average values of 59nGy-1, 370Bgkg-1 and 0.07mSvy-1 correspondingly. The excess lifetime cancer risk (ELCR) value obtained in this study for the ores samples ranges from 0.0026 to 0.0473 with an average of 0.0107 while the ELCR value in sediments samples was found to range from 0.3205 to 0.0036 with an average of 0.0620. Although the study reveals an average excess lifetime cancer risk value to be more in the sediment samples compare to ore samples, the excess lifetime cancer value within all the sample locations were above the world average value of 0.00029. Therefore, the present study reveals a lifetime cancer risk to the general public within this study area thus precaution need to be taken by ensuring inhabitants live in well ventilated houses since no level of radioactivity is harmless.