Evaluation of environmental and occupational exposure to mercury among Iranian dentists

The first ecological contamination study of avian mercury and lead in southeast Iran, Hamun International Wetlands

The concentrations of mercury (Hg) and lead (Pb) in feather samples of nine bird's species (n = 65) were determined from southeastern areas of Iran, Hamun International Wetlands. Hg concentrations were ranged from 0.40 to 3.00 mg/kg dry wt and from 0.38 to 1.76 mg/kg for primary and secondary feathers, respectively. Furthermore, Pb concentrations were ranged from 1.43 to 4.10 mg/kg and from 1.28 to 3.65 mg/kg for primary and secondary feathers, respectively. Deposition of metals varied significantly among the primary and secondary feathers of systematic category (families) for Hg and Pb (p < 0.001). It was found that there is a significant difference in feather Hg and Pb concentrations across species (p < 0.001) with highest concentrations in saker falcon (Falconidae) (Hg = 3.00 mg/kg and Pb = 4.10 mg/kg, primary feather) followed by little owl (Strigidae). Grey francolin (Phasianidae) contained the least amount of Hg (0.40 mg/kg) and Pb (1.43 mg/kg) in primary feather. The results showed that the highest concentrations of heavy metals were related to carnivores. Fish predators, omnivores, and insectivores were examined at the next level of metal concentration, with herbivores having the lowest concentrations of lead (1.43 mg/kg) and mercury (0.40 mg/kg). Birds with an open grasslands feeding strategy had the highest mercury and lead concentration. The average value for Pb was on the border of harmful effects (4 mg/kg). The results of this study indicate that mercury levels are lower than the threshold level for reproductive and behavioral harm (5 mg/kg).

Understanding the excretion rates of methylmercury and inorganic mercury from human body via hair and fingernails

Effective biomarkers are necessary to better understand the human mercury (Hg) exposure levels. However, mismatched biomarker sampling method causes extra uncertainty in assessing the risk of Hg exposure. To compare the differences between hair and fingernail, and further understand the excretion rates of methylmercury (MeHg) and inorganic mercury (IHg) via hair and fingernails, the total mercury (THg), MeHg, and IHg concentrations in paired hair and fingernail samples were investigated through paired samples collected from two typical mining areas, Wanshan mercury mine area (WMMA) and Hezhang zinc smelting area (HZSA). The positive correlation in THg, MeHg, and IHg concentrations (p <0.01) between hair and fingernail samples indicated that those two biomarkers can be corrected in application of assessing human Hg exposure. Compared to fingernails, the hair was suggested to be a more sensitive biomarker as the concentration of THg, MeHg and IHg were 2 ∼ 4 times higher than those in fingernails. Furthermore, the amounts of THg, MeHg, and IHg excreted via hair were 70 ∼ 226 times higher than that excreted via fingernails, and the hair plays a more important role than fingernails in the excretion of Hg from human bodies. Present study therefore provides some new insights to better understand the fate of human assimilated Hg.

Mercury level in biological samples of dentists in Iran: a systematic review and meta-analysis

Exposure to mercury is an important risk to dentists health. The aim of the present study was to assess the pooled mean mercury level (MML) in the urine, blood, nail, and hair of Iranian dentists (IDs) through the meta-analysis technique. Comprehensive and systematic searches were performed in main local databases including SID, Magiran, Iran medex, and ISC as well as internationally available databases including Embase, PubMed and Scopus for all the relevant studies up to 2018. In order to prevent bias in this study and identify eligible studies, various steps of the study was performed independently by two researchers. Out of 13 studies in the meta-analysis process which included 1499 IDs, the mean of the mercury level in the urine, nail, and blood was estimated to be 6.29 (95% CI: 2.61-9.97, I-square: 62.7%, P: 0.006), 3.54 (95% CI: 2.81-4.28, I-square: 0.0%, P: 0.968), 11.20 (95% CI: 2.28-20.13, I-square: 59.9%, P: 0.082), respectively. The mean mercury level (MML) in the biological samples of IDs was higher than the standard of World Health Organization (WHO). So, in accordance with Article 10 of the European Union Regulations (EUR), in the context of the Minamata Convention (MC) on Dental Amalgam (DA), in order to avoid the dangers of mercury exposure in dentists, it is necessary for Iran and other countries to approve laws and to implement a national plan to reduce mercury levels and replace the appropriate materials.

Occupational exposure to mercury vapor in a compact fluorescent lamp factory: Evaluation of personal, ambient air, and biological monitoring

Compact fluorescent lamps (CFLs) have become a popular lighting choice in recent years despite the good performance of light-emitting diode (LED) lamps. The CFLs that have been produced recently contain 1.5-3.5 mg Hg/lamp. There is evidence that even low doses of mercury are toxic. This study aimed to assess occupational exposure to mercury vapor in workers of a CFLs factory by determining mercury levels in personal and ambient air samples and urine of workers. This cross-sectional study was conducted on 59 workers in a CFLs factory in Iran. Personal and ambient air sampling of mercury vapor levels (MVLs) was performed during a workday. In total, 10 personal samples and 10 ambient air samples of mercury vapor were collected simultaneously from different units of the factory. Urine samples were collected before the work shift. Samples were analyzed using a cold-vapor atomic absorption spectrophotometer (CVAAS). The mean of the MVLs in the personal and ambient air samples was 14.78 ± 5.76 and 67.10 ± 59.37 µg.m^-3, respectively. The highest MVL was measured for the production line supervisor (25 µg.m^-3). There was a significant correlation between the MVLs in the ambient air and personal samples ( r = 0.84, p = 0.005). The mean urinary mercury level (UML) was 13.85 ± 13.14 µg/g creatinine. The UML of 86.4% workers was below the 20 µg/g creatinine recommended by the Centre of Environmental and Occupational Health in Iran. There were significant differences between the UMLs in different areas of the factory ( p = 0.041). Lamp breakage was an important determinant of exposure to mercury vapor; hence, effective programs to control mercury vapor are essential in the CFLs industry.

Baseline heavy metals in plant species from some industrial and rural areas: Carcinogenic and non-carcinogenic risk assessment

This paper provides the first quantitative information on accumulation of cadmium, lead, and arsenic in the soil, leaf, and root of wheat (Triticum aestivum L.), corn (Zea Maize), and tomato (Solanum lycopersicum) in the downstream agricultural lands of an industrial area and agricultural lands of a rural area, Razavi Khorasan province, Iran. The results showed that there is a significant difference among the cadmium concentrations in the soil, root and leaf/seed in various plants (p = 0.00 for wheat and corn and p = 0.0004 for tomato). There was no significant difference between the lead concentrations in the soil, root and leaf/seed in the case of wheat (p > 0.05), but there was a significant difference for other plants. Furthermore, statistical analysis was done on arsenic concentrations of soil, root and leaf/seed in the wheat, tomato, and corn. In the case of rural area, the results showed significant difference between the cadmium and lead concentrations of soil, root and leaf/seed in the wheat and tomato. In this area, statistical analysis was done on the arsenic concentrations of soil, root and leaf/seed in wheat, tomato, and corn (p = 0.00 for wheat, p = 0.00 for tomato, and p > 0.05 for corn). The heavy metals concentrations in some parts of the plants in the industrial area were above the standards. The concentrations of cadmium, lead, and arsenic for soil were below the limits proposed by WHO, EPA, and EU. In this study, the Total Hazard Quotient (THQ) through consumption of wheat was less than 1, indicating no significant potential health risk associated with the consumption of wheat from the areas. The cancer risk of arsenic from wheat consumption was as 255 × 10⁻⁶ and 0.00 in the industrial and rural areas, respectively.

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Atomic absorption spectrophotometer (AAS) equipped with graphite furnace was used for heavy metal analysis.

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The general results revealed that the levels of Cd, Pb, and As in the industrial area were higher than the rural area.

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The cancer risk of arsenic in wheat for the industrial area is greater than 1 × 10⁻⁶, which is unacceptable.

Measurement and modeling of particulate matter concentrations: Applying spatial analysis and regression techniques to assess air quality

This paper presented the levels of PM_2.5 and PM₁₀ in different stations at the city of Sabzevar, Iran. Furthermore, this study was an attempt to evaluate spatial interpolation methods for determining the PM_2.5 and PM₁₀ concentrations in the city of Sabzevar. Particulate matters were measured by Haz-Dust EPAM at 48 stations. Then, four interpolating models, including Radial Basis Functions (RBF), Inverse Distance Weighting (IDW), Ordinary Kriging (OK), and Universal Kriging (UK) were used to investigate the status of air pollution in the city. Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) were employed to compare the four models. The results showed that the PM_2.5 concentrations in the stations were between 10 and 500 μg/m³. Furthermore, the PM₁₀ concentrations for all of 48 stations ranged from 20 to 1500 μg/m³. The concentrations obtained for the period of nine months were greater than the standard limits. There was difference in the values of MAPE, RMSE, MBE, and MAE. The results indicated that the MAPE in IDW method was lower than other methods: (41.05 for PM_2.5 and 25.89 for PM₁₀). The best interpolation method for the particulate matter (PM_2.5 and PM₁₀) seemed to be IDW method.

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The PM₁₀ and PM_2.5 concentration measurements were performed in the period of warm and risky in terms of particulate matter at 2016.

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Concentrations of PM_2.5 and PM₁₀ were measured by a monitoring device, environmental dust model Haz-Dust EPAM 5000.

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Interpolation is used to convert data from observation points to continuous fields to compare spatial patterns sampled by these measurements with spatial patterns of other spatial entities.

Quantification of Hg excretion and distribution in biological samples of mercury-dental-amalgam users and its correlation with biological variables

This is the first study conducted to quantify the excretion and distribution of mercury (Hg) with time (days) in the biological samples collected from Hg dental amalgam users (MDA). The individuals, with Hg-based dental filling were selected, and their biological samples (red blood cells (RBCs), plasma, urine, hair, and nails) were collected on first, third, and 12th day of fillings. The concentrations of Hg observed in the biological samples of MDA were also correlated with the biological variables such as age, weight, restoration, fish consumption, number, and surface area of fillings. The concentrations of Hg in the biological samples of MDA were found 6-8 times higher than the non-amalgam users (control). The concentrations of Hg in the RBCs (4.39 μg/L), plasma (3.02 μg/L), and urine (22.5 μg/L) on first day of filling were found comparatively higher than the concentrations observed on third day (2.15, 1.46, and 12.3 μg/L for RBCs, plasma, urine, respectively) and 12th day (3.05, 2.5, 9.12 μg/L for RBCs, plasma, urine, respectively), while Hg concentrations were found lower in the hair and nails on third day of fillings (1.53 μg/g for hair and 2.35 μg/g for nails) as compared to the 12th day (2.95 μg/g for hair and 3.5 μg/g for nails). The correlations were found significant (p ˂ 0.05) between Hg concentrations in the biological samples of MDA and biological variables (the number of restoration, fish consumption, number, and surface area of fillings), while no significant (p ˃ 0.05) correlations were observed for Hg concentrations in the biological samples with age and weight of MDA. These observations unveil the fact that the use of Hg-based dental filling is the undesirable exposure to Hg which should be replaced by composite (a safer filling material).

Use of Mercury in Dental Silver Amalgam: An Occupational and Environmental Assessment

The objective of this study was to assess the occupational exposure to mercury in dentistry and associated environmental emission in wastewater of Lahore, Pakistan. A total of ninety-eight blood samples were collected comprising 37 dentists, 31 dental assistants, and 30 controls. Results demonstrate that the dentistry personnel contained significantly higher mean concentration of mercury in their blood samples (dentists: 29.835 µg/L and dental assistants: 22.798 µg/L) compared to that of the controls (3.2769 µg/L). The mean concentration of mercury was found maximum in the blood samples of older age group (62.8 µg/L) in dentists and (44.3 µg/L) in dental assistants. The comparison of mercury concentration among dentists, dental assistants, and controls (pairing based on their ages) revealed that the concentration increased with the age and experience among the dentists and dental assistants. Moreover, the mercury concentration in all the studied dental wastewater samples, collected from twenty-two dental clinics, was found to be exceeding the recommended discharge limit of 0.01 mg/L. Therefore, we recommend that immediate steps must be taken to ensure appropriate preventive measures to avoid mercury vapors in order to prevent potential health hazards to dentistry personnel. Strong regulatory and administrative measures are needed to deal with mercury pollution on emergency basis.

Mercury contamination in fish and human hair from Hainan Island, South China Sea: Implication for human exposure

Hair has long been recognized as a good biomarker for human exposure to Hg. The mercury concentrations in 14 species of marine fish and hair samples from 177 coastal residents in Hainan, South China Sea were investigated to assess the status of mercury exposure associated with marine fish consumption. Concentrations of total Hg (THg) and methylmercury (MeHg) in the fish muscles were 0.094 ± 0.008 and 0.066 ± 0.006 μg/gww, respectively, which were far below the limit considered safe for consumption (0.5 μg/g). The average THg concentrations in hair of adults (1.02 ± 0.92 μg/g) were lower than the provisional tolerable weekly intake (PTWI) level of 2.2 μg/g. However, 23.7% of children had a hair THg level exceeding the RfD level of 1μg/g, indicating a great risk of Hg exposure to children via fish consumption. The concentration of THg in hair was significantly correlated with fish consumption but not with gender-specific fish intake. With higher fish consumption frequency, the fishermen had significantly elevated hair Hg levels compared to the students and the other general public, who had similar hair THg levels but different fish consumption patterns, indicating the existence of other sources of Hg exposure to the residents of Hainan Island.

Determination of Mercury Exposure among Dental Health Workers in Nakhon Si Thammarat Province, Thailand

Objectives. The main objective of this study was to assess the mercury exposure levels in dental health workers that work in dental clinics. The study evaluated the airborne and urinary mercury levels, the type of work done in the clinic, and the effect of mercury exposure on health of dental health workers. Material and Methods. A case-control study was conducted with 124 exposed and 124 matched nonexposed subjects. Personal and area samplings were conducted to quantify mercury concentrations by solid sorbent tube. Urine samples were collected to determine mercury levels by cold-vapor atomic absorption spectrometer mercury analyzer. Results and Discussion. 17.6% (n = 32/182) of the air samples were higher than the occupational exposure limit (OEL). A multiple regression model was constructed. Significant predictors of urinary mercury levels included dietary consumption (fish or seafood), duration of work (yrs), work position, personal protection equipment used (PPE), and personal hygiene behaviors. Significant correlations were observed between mercury levels in urine and mercury in storage areas (r = 0.499, P < 0.05) and between mercury levels in urine and airborne mercury in personal samplings (r = 0.878, P < 0.001). Conclusion. Improvements in working conditions, occupational health training, and PPE use are recommended to reduce mercury exposure.

Current approaches of the management of mercury poisoning: need of the hour

Mercury poisoning cases have been reported in many parts of the world, resulting in many deaths every year. Mercury compounds are classified in different chemical types such as elemental, inorganic and organic forms. Long term exposure to mercury compounds from different sources e.g. water, food, soil and air lead to toxic effects on cardiovascular, pulmonary, urinary, gastrointestinal, neurological systems and skin. Mercury level can be measured in plasma, urine, feces and hair samples. Urinary concentration is a good indicator of poisoning of elemental and inorganic mercury, but organic mercury (e.g. methyl mercury) can be detected easily in feces. Gold nanoparticles (AuNPs) are a rapid, cheap and sensitive method for detection of thymine bound mercuric ions. Silver nanoparticles are used as a sensitive detector of low concentration Hg²⁺ ions in homogeneous aqueous solutions. Besides supportive therapy, British anti lewisite, dimercaprol (BAL), 2,3-dimercaptosuccinic acid (DMSA. succimer) and dimercaptopropanesulfoxid acid (DMPS) are currently used as chelating agents in mercury poisoning. Natural biologic scavengers such as algae, azolla and other aquatic plants possess the ability to uptake mercury traces from the environment.

Exposure to mercury among dental health workers in Turkey

Purpose:

To investigate the current status of exposure to mercury (Hg) among dental health workers in Turkey.

Methods:

A total of 115 persons working in the same hospital were included in the study and were divided into three groups. Group 1 consisted of 67 dentists; group 2 consisted of 21 dental personnel who work with amalgam, and group 3 consisted of 27 control subjects who work in the same hospital but are non-dental personnel. The number of amalgam fillings that have been made by the dentists and the number of own fillings of the subjects were recorded.

Results:

Plasma Hg levels were found to be 3.76 ± 1.84, 3.54 ± 1.83, and 2.69 ± 0.97 µg/L in groups 1, 2, and 3, respectively. Hg concentrations in group 1 were significantly higher than the control group. There was no significant difference between groups 1 and 2. The number of amalgam fillings made by the dentists in the previous year correlated significantly with plasma Hg levels ( r = 0.378, p < 0.01). There was no significant correlation between the own amalgam fillings in the teeth of the subjects and Hg levels.

Conclusion:

Preventive measures for protection from exposure to Hg are necessary for occupational health in dentistry and proper industrial hygiene rules should be emphasized to avoid contamination during work.

Hair mercury concentrations of lactating mothers and breastfed infants in Iran (fish consumption and mercury exposure)

Coastal populations with high seafood consumption in the South Caspian Sea (Iran) have a significant exposure to dietary mercury. This study assesses the biomonitoring of mercury in mothers and breastfed infants in the South Caspian Sea. The mean of mercury concentration in the hair of 93 pairs of mothers and infants was obtained and was 3.55 and 1.89 μg g(-1), respectively. A statistically significant correlation (R = 0.850, P = 0.000) was seen between mercury concentration in the hair of mothers and infants. The results of this study indicate that hair mercury concentrations exceeded the USEPA reference dose of 1 μg g(-1) in 82.7 % of mothers and 61.2 % of infants. Also, 31 % of the mothers and 10.7 % of the infants had mercury concentrations more than the WHO "threshold" level (5 μg g(-1)). The age and fish consumption of mothers were the factors that significantly affected the hair mercury concentration of mothers and infants. Number of dental amalgam fillings of mothers was the factor that only affected mercury in the hair of mothers. According to the results, we can conclude that the main determinant of mercury exposure was the intake of mercury through fish consumption of mothers.

Improper waste disposal of silver-mercury amalgam

The objective of this work was to estimate the quantity of mercury residue present in dental amalgam that is generated and discarded in the city of Manaus (Amazon-Brazil). For this purpose, the locations of amalgam usage (10 public and 31 private dental clinics), the method by which the residue is discarded (14 clinics improper disposal), and the analysis of total mercury in the sediment of the controlled landfill (2.68-3 μgHg/g), were described. It was concluded that: there are dental clinics in the city that discard mercury residue into the common waste disposal system, which contravenes health safety standards.

Mercury (Hg) burden in children: the impact of dental amalgam

The risks and benefits of using mercury (Hg) in dental amalgam have long been debated. This study was designed to estimate Hg body burden and its association with dental amalgam fillings in 182 children (ages: 5-15 years) living in Taif City. Hg was measured in urine (UHg), hair (HHg) and toenails (NHg) by the Atomic Absorption Spectrophotometer with Vapor Generator Accessory system. Urinary Hg levels were calculated as both micrograms per gram creatinine (μg/g creatinine) and micrograms per liter (μg/L). We found that children with amalgam fillings (N=106) had significantly higher UHg-C levels than children without (N=76), with means of 3.763 μg/g creatinine versus 3.457 μg/g creatinine, respectively (P=0.019). The results were similar for UHg (P=0.01). A similar pattern was also seen for HHg, with means of 0.614 μg/g (N=97) for children with amalgam versus 0.242 μg/g (N=74) for those without amalgam fillings (P=0). Although the mean NHg was higher in children without amalgam (0.222 μg/g, N=61) versus those with (0.163 μg/g, N=101), the relationship was not significant (P=0.069). After adjusting for many confounders, the multiple logistic regression model revealed that the levels of UHg-C and HHg were 2.047 and 5.396 times higher, respectively, in children with dental amalgam compared to those without (P<0.01). In contrast, a significant inverse relationship was seen between NHg levels and dental amalgam fillings (P=0.003). Despite the controversy surrounding the health impact of dental amalgam, this study showed some evidence that amalgam-associated Hg exposure might be related with symptoms of oral health, such as aphthous ulcer, white patches, and a burning-mouth sensation. Further studies are needed to reproduce these findings. The present study showed that significant numbers of children with or without amalgam had Hg levels exceeding the acceptable reference limits. The detrimental neurobehavioral and/or nephrotoxic effects of such an increased Hg on children should be a cause of concern, and further investigation is warranted. Our results are alarming and indicate an urgent need for biomonitoring and assessment of exposure. Changes in dental practices involving amalgam, especially for children, are highly recommended in order to avoid unnecessary exposure to Hg.

Impact of occupational exposure to elemental mercury on some antioxidative enzymes among dental staff

OBJECTIVES

The aim of this study is to investigate the effect of elemental mercury exposure on renal function and antioxidative enzymes activity as a possible mechanism of renal affection among dental staff.

METHODS

This study was performed on a group of dental staff exposed to elemental mercury (N = 32) and matched control group (N = 37). Urinary and blood level of mercury, albumin α1 microgloblin in urine, glutathione peroxidase and superoxide dismutase blood level were measured for the exposed and control group.

RESULTS

Compared to the control group, urinary and blood mercury were significantly higher in the exposed group. Glutathione peroxidase and superoxide dismutase activities in blood were significantly decreased and were negatively correlated with duration of work.

CONCLUSION

Oxidative stress is an important molecular mechanism for renal dysfunction in mercury exposure, manifested by decreased activities of antioxidant enzymes.

Hair mercury levels in pregnant women in Mahshahr, Iran: fish consumption as a determinant of exposure

MeHg is a well-documented neurotoxicant even at low levels of exposure. Developing brain, in particular, is vulnerable to that. Through bioaccumulating to differing degrees in various fish species, it can have serious adverse effects on the development and functioning of the human central nervous system, especially during prenatal exposure. Therefore, the purpose of this study was to investigate mercury concentration in hair samples of pregnant women living in Mahshahr located in Khuzestan province, Iran. It assessed the association between fish consumption and specific characteristics that can influence exposure. From April to June 2008, 149 pregnant women were invited to participate in this study. An interview administered questionnaire was used to collect information about age, body weight, height, fish (fresh, canned and shrimp) consumption, pregnancy stage, residence duration, education level, family income and number of dental amalgam fillings. The obtained results showed that the geometric mean and range for hair total Hg concentration was 3.52 microg/g (0.44-53.56 microg/g). About 5.4% of mothers had hair total Hg levels in excess of 10 microg/g. Maternal hair mercury level was less than threshold level of WHO (5 microg/g). As expected, there was a clear increase in hair Hg with reported fresh marine fish consumption (p=0.04). The highest mean for hair mercury level in a group who consumed fish several times per week, was 4.93 microg/g. Moreover, a significant effect of age and residential time on Hg concentration in the hair of the women was found. Pregnant women in Mahshahr consumed large amounts of fish; consequently, most of their offspring were prenatally exposed to moderately high levels of mercury. The results found suggest that pregnant women should decrease their fish consumption.

Mercury exposure assessment in Iranian women's hair of a port town with respect to fish consumption and amalgam fillings

In this study we aimed to estimate the level of mercury in women's hair and its association with fish consumption and amalgam fillings in an Iranian southern port town (named Mahshahr). A total number of 195 hair samples were collected randomly from women aged 25-45 years free from occupational exposures to mercury. Additional information about these women's age, weight, height, number of pregnancies, level of education, number of amalgam fillings and fish consumption were also gathered. The determination of Hg level in hair samples was carried out by the LECO, AMA 254, Advanced Mercury Analyzer, according to ASTM standard No. D-6722. The average mercury level in these women's hair was 2.95+/-2.33microg/g (ranged from 0.07 to 24.46microg/g). In the next stage, the study participants were divided into four groups with respect to their fish consumption and number of amalgam fillings; A) <3 amalgam fillings, <3 times fish consumption per month, B) <3 amalgam fillings, >7 times fish consumption per month, C) >6 amalgam fillings, <3 times fish consumption per month, and D) >6 amalgam fillings, >7 times fish consumption per month. Statistical analysis showed that the Hg level was significantly different in these four groups (P<0.001). Mercury levels in this sample exceeded the USEPA-recommended 1microg/g in 76.4% of the studied population. Finally, the multiple linear regression results revealed that frequency of fish consumption and amalgam restorations are the most important routes of Hg exposure. However, the main determinant of Hg exposure was the intake of Hg through fish consumption.

Hair mercury concentration and fish consumption: risk and perceptions of risk among women of childbearing age

The purposes of this study were to assess the hair mercury concentration of women of childbearing age in Taiwan, and to calculate a hazard quotient (HQ) to evaluate the risk of fish consumption for these women. We also examined perceptions of risk associated with fish consumption and whether women in our study changed their habits in response to such risks. The average concentration of mercury was 1.73+/-2.12microgg(-1) (range: 0.02-16.34microgg(-1)), exceeding the US EPA reference dose of 1microgg(-1) in 52.9% of study subjects. The WHO tolerance limit of 10microgg(-1) was exceeded in 1.5% of study subjects. Hair mercury concentration in groups who consumed fish was significantly higher than in groups who never consumed fish (p<0.05). The hazard quotient (exposure estimate/oral reference dose) exceeded 1.0 for 29% of subjects, based on the US EPA's reference dose (0.1microgkg(-1)d(-1)), and the average HQ equaled 1.26. When told that some fish contain high levels of mercury that may be harmful for unborn babies, 67.6% of women still indicated that they would not change their amount of fish intake. The high hair mercury concentrations among women of childbearing age in Taiwan are a cause for concern, due to the effect on babies' brain development. The government should provide specific information about risks and benefits of fish consumption for women to make risk-balancing decisions.

A multispecies-monitoring study about bioaccumulation of mercury in Iranian birds (Khuzestan to Persian Gulf): Effect of taxonomic affiliation and trophic level

In the present study, the first baseline concentration of mercury (Hg) in different species of Iranian birds was investigated. From April to October 2005, the tail feathers of 100 birds belonging to 27 species (14 families) from different places in southwest Iran (Khuzestan to Persian Gulf) were collected. The Hg levels were evaluated in relation to taxonomic affiliation and trophic level (type of food). The results showed that the Hg levels in the feathers were between 0.07 and 4.71mg/kg dry weight (dw), and there was a significant effect of taxonomic groups in relation to Hg concentration (p<0.001). The highest mercury concentrations were in Laridae and Ciconidae. Alcedinidae had intermediate values, whereas Upupidae, Glareolidae, Scolopacidae, Turdidae, Ardeidae, Anatidae were in subsequent orders; and the lowest concentrations of Hg were in Rallidae, Cuculidae, Pycnonotidae, Corvidae and Columbidae. The results indicated a significant difference between the trophic levels (p<0.001). Fish predators had the highest level of Hg (3.07mg/kg). Invertebrate predators and herbivorous birds had the lowest concentration of Hg (0.84 and 0.64mg/kg, respectively), whereas crab and fish predators and omnivorous birds had moderate values (1.73 and 1.70mg/kg, respectively). In the present study, the concentration of Hg was significantly higher in tail feathers than in primary and secondary (p<0.001). A significant positive correlation among Hg concentration of feather types was observed (r>0.96). The results obtained in this study indicated that among 100 birds tested, 6% of them had Hg concentrations greater than 5mg/kg in feather (adverse level).

Blood levels of lead, cadmium, and mercury in residents of Tehran

Monitoring of toxic trace elements for human blood has been of interest to researchers in the fields of environmental chemistry and medical science. The amount of blood toxic elements can reflect the disease state of the person or the environment where that person resides or works. Chronic, low-level exposure to toxic metals such as lead (Pb), cadmium (Cd), and mercury (Hg) is an increasing global problem. This study focuses on obtaining the usual value of Pb, Cd, and Hg in normal human blood. These elements were determined in 61 male and 40 female volunteers resident in Tehran (Iran). The subjects were non-drug abusers and aged 6-62 years old. Procedures were developed for the collection, storage, and preanalytical treatment of samples. The lead and cadmium were determined by graphite furnace atomic absorption spectrometry, and mercury was measured by cold vapor atomic absorption spectrometry technique. The blood levels of Pb, Cd, and Hg in normal volunteers living in Tehran were 123.75 +/- 56.42, 1.82 +/- 0.67, and 8.48 +/- 4.42 microg/L. There was no significant gender-related difference in blood Cd and Hg concentrations (p < 0.06 and p < 0.41). However, the results indicated significantly higher content of Pb in blood of males compared to females (138.11 +/- 65.43 and 101.84 +/- 51.38 microg/L, respectively, p < 0.05).