Arsenism Clinical Stages and their Relation with Hair Arsenic Concentration of Residents of Bayinmaodao Rural District, Inner Mongolia, China

The clinical skin lesions of arsenism in men and women in Bayinmaodao rural district in Inner Mongolia, Peoples Republic of China, have been examined by doctors, and their hair and drinking water samples analysed for arsenic by hydride generation and ICP-AES. Altogether 311 arsenism patients with a 15.53% prevalence rate for the district were recorded. The disease prevalence rate was positively related to population, age, and their exposure to elevated arsenic concentrations in the drinking water from 1983 when new wells were dug and drinking of surface water was abandoned. Hyperkeratosis was the most serious skin lesion with the highest occurrence rate, then depigmentation and pigmentation in decreasing order. With increasing severity of the disease, ranging from skin lesion with single hyperkeratosis 1° to hyperkeratosis 3° with depigmentation 3° and pigmentation 3°, the results showed that arsenic concentrations in head hair had increased. Arsenic concentrations in hair were positively correlated with the arsenic concentrations in drinking water obtained from local wells.     

Health Risks Associated with Contamination of Groundwater by Abandoned Mines Near Twisp in Okanogan County, Washington, USA

Abandoned mines are known to contaminate private drinking water wells with toxic metals and arsenic (As). Little attention is given, however, to sites in rural areas with low population densities where natural, geogenic sources of contaminants might also occur. This study measured arsenic and trace element exposure among residents consuming water from wells adjacent to abandoned mines near Twisp, in Okanogan County, Washington, USA, estimated the risk of adverse health effects, and considered the degree of uncertainty associated with the assessed risk. Water samples were collected between October 1999 and June 2001. Average As concentrations ranged from <1 to 298 microg L(-1), lead (Pb) ranged from 0 to 94 microg L(-1), cadmium (Cd) 0-5 microg L(-1), and selenium (Se) 0-390 microg L(-1). Concentrations varied seasonally with maximum concentrations occurring in conjunction with snow-melt. The calculated risk of mortality from cancer following exposure to As at average concentrations as low as 8 microg L(-1) was greater than one in 10,000. Additional noncarcinogenic risks are associated with exposure to As, Cd, Pb and Se. A potentially affected population, estimated to be between 1000 and 1287 residents, live within a 6.5-km (4-mile) radius of the study site. This study emphasises the need to test drinking water wells in the vicinity of abandoned mines during times of maximum snow-melt to determine the extent of risk to human health. Residents drinking water from wells tested in this study who want to reduce the estimated carcinogenic risk and the noncarcinogenic hazard quotient should consider treating their water or find alternative sources.     

Arsenic and other trace elements in groundwater and human urine in Ha Nam province,the Northern Vietnam: contamination characteristics and risk assessment

The contamination characteristics of arsenic and other trace elements in groundwater and the potential risks of arsenic from the groundwater were investigated. Elevated contamination of arsenic, barium and manganese was observed in tube-well water of two villages (Chuyen Ngoai and Chau Giang) in Ha Nam province in the Northern Vietnam. Concentrations of As in the groundwater ranged from 12.8 to 884 µg/L with mean values in Chuyen Ngoai and Chau Giang were 614.7 and 160.1 µg/L, respectively. About 83 % of these samples contained As concentrations exceeding WHO drinking water guideline of 10 μg/L. The mean values of Mn and Ba in groundwater from Chuyen Ngoai and Chau Giang were 300 and 657 μg/L and 650 and 468 μg/L, respectively. The mean value of Ba concentration in groundwater in both Chuyen Ngoai and Chau Giang was about 22 % of the samples exceeded the WHO guideline (700 µg/L). Arsenic concentrations in human urine of residents from Chuyen Ngoai and Chau Giang were the range from 8.6 to 458 µg/L. The mean values of Mn and Ba in human urine of local people from Chuyen Ngoai were 46.9 and 62.8 μg/L, respectively, while those in people from Chau Giang were 25.9 and 45.9 μg/L, respectively. The average daily dose from ingesting arsenic for consuming both untreated and treated groundwater is from 0.02 to 11.5 and 0.003 to 1.6 μg/kg day, respectively. Approximately, 57 % of the families using treated groundwater and 64 % of the families using untreated groundwater could be affected by elevated arsenic exposure.     

Chinese population exposure to triclosan and triclocarban as measured via human urine and nails

Triclosan (TCS) and triclocarban (TCC) exposures are highly concerned due to their suspected endocrine-disrupting effects. The present study investigated TCS and TCC exposure levels in the general Chinese population by biomonitoring human urine and nail samples. TCS (69–80 %) and TCC (99–100 %) were frequently detected, which demonstrates that the general Chinese population has extensive exposure to these chemicals. The geometric mean (GM) urinary concentrations were 0.40 μg/g creatinine (creat), 95 % confidence interval (CI) 0.30–0.56, for TCS and 0.40 μg/g creat, 95 % CI 0.29–0.56, for TCC. On the other hand, the GM levels of TCS and TCC were 13.57 (5.67 μg/kg) and 84.66 μg/kg (41.50 μg/kg) in fingernail (toenail) samples, respectively, indicating that the levels in fingernails were approximately twice as high as those in toenails. Pearson’s correlation coefficients between the urine and fingernail (toenail) samples were 0.715 (0.614) for TCS and 0.829 (0.812) for TCC. These data suggest that nail samples can be applied to the biomonitoring for TCS and TCC in the general population. We observed that the levels of both chemicals were higher in females than in males for urine and fingernail samples, but no significant differences were found between different genders for either compound in toenails. Nineteen- to 29-year-olds had the highest TCS levels in their nail samples, whereas TCC levels did not differ with regard to age. Region of residence significantly influenced TCS and TCC concentrations in the three biological matrices measured.     

Chronic exposure of arsenic via drinking water and its adverse health impacts on humans

Worldwide chronic arsenic (As) toxicity has become a human health threat. Arsenic exposure to humans mainly occurs from the ingestion of As contaminated water and food. This communication presents a review of current research conducted on the adverse health effects on humans exposed to As-contaminated water. Chronic exposure of As via drinking water causes various types of skin lesions such as melanosis, leucomelanosis, and keratosis. Other manifestations include neurological effects, obstetric problems, high blood pressure, diabetes mellitus, diseases of the respiratory system and of blood vessels including cardiovascular, and cancers typically involving the skin, lung, and bladder. The skin seems to be quite susceptible to the effects of As. Arsenic-induced skin lesions seem to be the most common and initial symptoms of arsenicosis. More systematic studies are needed to determine the link between As exposure and its related cancer and noncancer end points.     

Long-distance transport of Hg, Sb, and As from a mined area, conversion of Hg to methyl-Hg, and uptake of Hg by fish on the Tiber River basin, west-central Italy

Stream sediment, stream water, and fish were collected from a broad region to evaluate downstream transport and dispersion of mercury (Hg) from inactive mines in the Monte Amiata Hg District (MAMD), Tuscany, Italy. Stream sediment samples ranged in Hg concentration from 20 to 1,900 ng/g, and only 5 of the 17 collected samples exceeded the probable effect concentration for Hg of 1,060 ng/g, above which harmful effects are likely to be observed in sediment-dwelling organisms. Concentrations of methyl-Hg in Tiber River sediment varied from 0.12 to 0.52 ng/g, and although there is no established guideline for sediment methyl-Hg, these concentrations exceeded methyl-Hg in a regional baseline site (<0.02 ng/g). Concentrations of Hg in stream water varied from 1.2 to 320 ng/L, all of which were below the 1,000 ng/L Italian drinking water Hg guideline and the 770 ng/L U.S. Environmental Protection Agency (USEPA) guideline recommended to protect against chronic effects to aquatic wildlife. Methyl-Hg concentrations in stream water varied from <0.02 to 0.53 ng/L and were generally elevated compared to the baseline site (<0.02 ng/L). All stream water samples contained concentrations of As (<1.0–6.2 μg/L) and Sb (<0.20–0.37 μg/L) below international drinking water guidelines to protect human health (10 μg/L for As and 20 μg/L for Sb) and for protection against chronic effects to aquatic wildlife (150 μg/L for As and 5.6 μg/L for Sb). Concentrations of Hg in freshwater fish muscle ranged from 0.052–0.56 μg/g (wet weight), mean of 0.17 μg/g, but only 17 % (9 of 54) exceeded the 0.30 μg/g (wet weight) USEPA fish muscle guideline recommended to protect human health. Concentrations of Hg in freshwater fish in this region generally decreased with increasing distance from the MAMD, where fish with the highest Hg concentrations were collected more proximal to the MAMD, whereas all fish collected most distal from Hg mines contained Hg below the 0.30 μg/g fish muscle guideline. Data in this study indicate some conversion of inorganic Hg to methyl-Hg and uptake of Hg in fish on the Paglia River, but less methylation of Hg and Hg uptake by freshwater fish in the larger Tiber River.     

High soil and groundwater arsenic levels induce high body arsenic loads,health risk and potential anemia for inhabitants of northeastern Iran

Arsenic bioavailability in rock, soil and water resources is notoriously hazardous. Geogenic arsenic enters the body and adversely affects many biochemical processes in animals and humans, posing risk to public health. Chelpu is located in NE Iran, where realgar, orpiment and pyrite mineralization is the source of arsenic in the macroenvironment. Using cluster random sampling strategy eight rocks, 23 soils, 12 drinking water resources, 36 human urine and hair samples and 15 adult sheep urine and wool samples in several large-scale herds in the area were randomly taken for quantification of arsenic in rock/soil/water, wool/hair/urine. Arsenic levels in rock/soil/water and wool/hair/urine were measured using inductively coupled plasma spectroscopy and atomic absorption spectrophotometry, respectively. While arsenic levels in rocks, soils and water resources hazardously ranged 9.40–25,873.3 mg kg^?1, 7.10–1448.80 mg kg^?1 and 12–606 μg L^?1, respectively, arsenic concentrations in humans’ hair and urine and sheep’s wool and urine varied from 0.37–1.37 μg g^?1 and 9–271.4 μg L^?1 and 0.3–3.11 μg g^?1 and 29.1–1015 μg L^?1, respectively. Local sheep and human were widely sick and slightly anemic. Hematological examination of the inhabitants revealed that geogenic arsenic could harm blood cells, potentially resulting in many other hematoimmunological disorders including cancer. The findings warn widespread exposure of animals and human in this agroecologically and geopolitically important region (i.e., its proximity with Afghanistan, Pakistan and Turkmenistan) and give a clue on how arsenic could induce infectious and non-infectious diseases in highly exposed human/animals.     

Quality of tube well water intended for irrigation and human consumption with special emphasis on arsenic contamination at the area of Punjab,Pakistan

In the present study, the tube well water quality and the associated health risks, emphasizing on arsenic contamination, were investigated in rural and urban samples from Tehsil Mailsi located in Punjab, Pakistan. Arsenic concentrations (μg/L) were ranged from 12 to 448.5 and which exceeded the WHO recommended limit (10 μg/L) in all cases. The calculated average daily dose (3.3 × 10^?0.4 to 1.2 × 10^?0.2 mg/kg day) and hazard quotient (1.1–40) reflected the potential health risk to local population due to tube well water consumption as drinking purpose. Sodium percent (Na%), sodium absorption ratio, residual sodium carbonate, Kelly’s index and magnesium absorption ratio were also determined to assess the suitability of tube well water for irrigation purpose. The resulting piper plot revealed the Na–Ca–HCO₃ type water chemistry of the area and generally alkaline environment. The spatial distribution of arsenic in the tube well waters pinpoints the significant contribution of anthropogenic activities to arsenic pollution. Nevertheless, different statistical tools, including principal component analysis, hierarchical cluster analysis and correlation matrices, revealed the contribution of both natural and anthropogenic activities and alkaline type of aquifers toward the high level of arsenic contamination.     

Health risk assessment of groundwater arsenic pollution in southern Taiwan

Residents of the Pingtung Plain, Taiwan, use groundwater for drinking. However, monitoring results showed that a considerable portion of groundwater has an As concentration higher than the safe drinking water regulation of 10 μg/L. Considering residents of the Pingtung Plain continue to use groundwater for drinking, this study attempted to evaluate the exposure and health risk from drinking groundwater. The health risk from drinking groundwater was evaluated based on the hazard quotient (HQ) and target risk (TR) established by the US Environmental Protection Agency. The results showed that the 95th percentile of HQ exceeded 1 and TR was above the safe value of threshold value of 10^?6. To illustrate significant variability of the drinking water consumption rate and body weight of each individual, health risk assessments were also performed using a spectrum of daily water intake rate and body weight to reasonably and conservatively assess the exposure and health risk for the specific subgroups of population of the Pingtung Plain. The assessment results showed that 0.01–7.50 % of the population’s HQ levels are higher than 1 and as much as 77.7–93.3 % of the population being in high cancer risk category and having a TR value >10^?6. The TR estimation results implied that groundwater use for drinking purpose places people at risk of As exposure. The government must make great efforts to provide safe drinking water for residents of the Pingtung Plain.     

A seasonal study of arsenic in groundwater,Snohomish County,Washington, USA

A series of arsenic poisonings near Granite Falls in Snohomish County, Washington, were identified during 1985–87. An initial investigation revealed the source of arsenic exposure to be high levels of arsenic in well water. A large number of wells in eastern Snohomish County were tested, residents were interviewed and sources of contamination, both natural and man-made, were investigated. More than 70 private drinking-water wells were found to contain elevated levels of arsenic . One well contained 33 mg As L^–1. The finding of elevated arsenic levels in a previously approved drinking-water well for a restaurant, plus suggestions of symptoms consistent with arsenic poisoning among people with wells with no detectable arsenic, raised concern over possible temporal variation in arsenic levels. To evaluate this temporal variation, a 12-month study of arsenic in groundwater was conducted in selected wells near Granite Falls. The 12-month study of 26 wells, conducted between February 1988 and January 1989, found arsenic levels for individual wells to vary from one to 19 fold over time. Because of this variability, four out of the eight wells with arsenic levels close to the Maximum Contamination Level (MCL) of 0.050 mg As L^–1 would have been considered safe on the basis of a single sample, but would have exceeded the MCL at another time of the year.In areas with a high occurrence of arsenic contaminated drinking water, approval of well water prior to the sale of a house or issuance of a building permit which is based on a single arsenic test may result in later findings of unacceptable drinking water. When the arsenic is near the MCL, it may be prudent to follow well-water arsenic concentrations over time to assure that the arsenic level remains within acceptable bounds. If lower arsenic standards are adopted for drinking water, the issue of temporal variation around the standard will become a matter of more widespread concern.To whom correspondence should be addressed. The contents of this paper do not necessarily reflect the views and policies of the US Environmental Protection Agency.     

Health risk of arsenic in the alluvial aquifers of Lahore and Raiwind,Punjab Province,Pakistan: an investigation for safer well water

Environmental pollution has generated release of high amounts of arsenic (As) which ultimately are detected in the water of Indus Basin Punjab, Pakistan. The area is characterized by a semiarid climate, and alluvial deposits. This investigation, an extension of previously reported As-affected area in Lahore and Kasur, aimed to (1) assess the extent of water contamination in this area and (2) determine possible safer sites for future water use. In a comparative study, total As contamination of underground water from individual dwellings and community water supply of some villages located at the boundary of the Sheikhopura and Lahore districts, Pakistan were measured to compare with previously published data of villages located at the boundary of the Lahore and Kasur districts. The results showed variable levels of As in shallow drinking water wells and average concentration exceeding WHO guidelines value. As levels ranged from below 5.2 to 80 µg/L and mean 45.5 µg/L. The As concentrations were higher than WHO limits but lower than previous studied area. In addition, high salinity was found to be a serious concern for deteriorating groundwater quality rendering it unsuitable for drinking. Groundwater is predominantly of the Na–HCO₃ type with slightly alkaline pH. High pH values and competition of As with HCO₃ may serve as an important process for mobilization of As in the shallow groundwater of the region. Continuous monitoring and expansion of monitoring systems are necessary to establish safer wells within As-contaminated areas.     

Association between skin lesion and arsenic concentration in hair by mixed bivariate model in chronic arsenic exposure

Skin lesion is one of the important health hazards caused by high intake of arsenic through drinking water and diet, and the other hazards include several types of cancers (viz. skin, lung and urinary bladder), ischemic heart disease, hypertension, etc. Two most important biomarkers to measure arsenic intake in a human body are arsenic concentration in urine and hair. The primary interest of this paper is the association between skin lesion and arsenic concentration in hair for participants with chronic arsenic exposure from West Bengal, India, using bivariate regression model based on copula function. The result showed participants with high arsenic concentration in hair had higher incidence of developing skin lesion. Arsenic concentration in hair was significantly higher for the participants with an arsenic concentration in water?>?10 mg/L.     

Urinary cadmium concentrations in a population downstream: from a zinc mining area in Mae Sot District, Tak Province, Thailand

Urinary cadmium (UCd) is a good indicator of long-term exposure to cadmium. UCd concentrations resulting from juvenile cadmium exposure in 3 sub-districts of Tak Province, Thailand, were investigated. The target population was divided by gender and into 2 age subgroups: 9–12 and 13–15 years. A total of 748 urine samples were collected and analyzed by spectrophotometer. All samples had UCd of more than 1.0 μg/g creatinine (Cr). Total UCd means among the 3 sub-districts were 1.31, 1.01, and 0.87 μg/g Cr; the Thai population mean is 0.5 μg/g. The difference among the three sub-districts was statistically significant (p < 0.05). Total means for UCd were 1.13 μg/g Cr for boys, 1.00 for girls, 1.01 μg/g Cr for those 9–12 years old, and 1.18 for those 13–15. UCd concentrations were not significantly different between genders and age groups. Likely dietary sources of cadmium exposure for the subject population were surveyed.     

Geochemical occurrences of arsenic and fluoride in bedrock groundwater: a case study in Geumsan County,Korea

Bedrock groundwaters in Geumsan County, Korea, were surveyed to investigate the distribution and geochemical behaviors of arsenic and fluoride, mobilized through geogenic processes. The concentrations were enriched up to 113 μg/L for arsenic and 7.54 mg/L for fluoride, and 16% of 150 samples exceeded World Health Organization drinking water guidelines for each element. Simple Ca-HCO₃ groundwater types and positive correlations with pH, Ca, SO₄, and HCO₃ were characteristics of high (>10 μg/L) As groundwaters. The oxidation reaction of sulfide minerals in metasedimentary rocks and locally mineralized zones seems to be ultimately responsible for the existence of arsenic in groundwater. Desorption process under high pH conditions may also control the arsenic mobility in the study area. High (>1.5 mg/L) F groundwaters were found in the Na-HCO₃ type and with greater depth. Fluoride seemed to be enriched by deep groundwater interaction with granitic rocks, and continuous supply to shallow Ca-HCO₃-type groundwater kept the concentration high. In the study area, drinking water management should include periodic As and F monitoring in groundwater.

     

广州市饮用水中挥发性有机物的研究

饮用水中的挥发性有机化合物（VOCs）来源于水源水受到的环境污染或是在净化消毒工艺处理工程中反应产生的副产物,可对人体健康造成极大的危害。改革开放以来,广州人口和经济得到突飞猛进的发展,也带来了包括饮用水安全在内的诸多严重的社会和环境问题。虽然饮用水中VOCs的研究已经得到越来越多的重视,但是目前对广州市饮用水中挥发性有机物的研究还鲜有报道。本文在广州市中心城区选取15个不同位置的采样点进行了自来水水样采集,并利用吹扫-捕集-气相色谱-质谱（GC-MS）联用系统分析技术测定水中 VOCs 的种类和三卤甲烷的质量浓度。结果表明,广州市中心城区的自来水中VOCs有20种,以三卤甲烷（THMs）和芳香烃类为主,占了所检出的物质总量的78%以上。THMs中四种化合物（氯仿、一溴二氯甲烷、二溴一氯甲烷、溴仿）的检出率达100%,总三卤甲烷的平均质量浓度为46.46μg· L-1,最大值为53.31μg· L-1,最小值39.91μg· L-1。根据2006版国家饮用水标准,四种三卤甲烷质量浓度均低于标准限值,符合标准要求。对市面上一般的瓶装水的研究发现,瓶装水中三卤甲烷的质量浓度非常低,总三卤甲烷平均质量浓度仅为1.47μg·L-1,约是自来水中质量浓度的1/30。为了解温度及煮沸对自来水中 THMs 质量浓度的影响,本研究设计了实验进行探究。结果发现加热至沸腾过程中,THMs质量浓度随温度升高而升高,而沸腾后THMs骤降,煮沸5 min可降低水中约95%的THMs,接近瓶装水中THMs质量浓度。     

Selenium and arsenic content of agricultural soils from Bangladesh and Nepal

Arsenic (As) contamination of the available domestic drinking water from shallow aquifers to villagers in Bangladesh often exceeds the newest WHO standard of <10 µg As L^?1 and the older Bangladeshi standard of <50 µg As L^?1. An estimated 9.2 million shallow tube wells in Bangladesh deliver water to 97% of the rural population, placing an estimated 57 million people at risk for arsenicosis. The contamination of drinking water by As extends to W. Bengal, India and Nepal. The same shallow aquifers used for domestic water are also used to irrigate food crops, particularly rice. Irrigation adds As to soils and increases exposure of the population to additional As via foods consumed. Selenium (Se), an essential trace mineral found in soils, is absorbed by plants, entering the human food chain. It was suggested that a low dietary intake of Se may be contributing to the problem of human arsenicosis in Bangladesh. Dietary Se acts as a natural antidote to As by (1) accelerating As excretion, (2) sequestering As by complexation and (3) as an antioxidant component of the enzyme glutathione peroxidase that may counteract the prooxidant effects of As that contribute to arsenicosis and cancer. Analysis of 70 agricultural soil samples from Bangladesh by fluorimetry, ICP-AES and Neutron Activation Analysis showed the soils analyzed to be high in As (～33 µg g^?1) and biologically low in soluble Se (～0.02 µg g^?1). A low dietary intake of Se related to low soil content and this mineral in foods may be contributing to human arsenicosis in the Ganges–Brahmaputra delta.     

杀虫剂三唑磷在室内淡水微宇宙中的生态效应

作为一种中等毒性的有机磷杀虫剂,三唑磷在稻区的使用十分普遍。为弄清其对淡水生态系统的影响,选择5组浓度(0、0.35、1.75、17.5、52.5μg·L~(-1)),在以藻类作为营养源的室内微宇宙系统内进行研究,采用多变量分析软件CANOCO 5对数据进行分析。非限制性排序和多重比较的结果表明,给药后0~6 d,三唑磷对于浮游动物群落的最高无作用浓度(NOEC_(community))和最低有效浓度(LOEC_(community))分别为17.5μg·L~(-1)和52.5μg·L~(-1)。给药后第9天,最高浓度组(52.5μg·L~(-1))的群落结构开始恢复,此刻三唑磷在水中的实测浓度平均值为4.35μg·L~(-1)。对于单个物种种群密度做差异显著性分析和多重比较,结果显示浮游动物当中受影响最大的是绿色湖湾介Strandesia viridis。给药30 d后,该物种在52.5μg·L~(-1)处理组的种群密度明显下降,历时57 d的试验结束时,种群密度仍未恢复到对照水平。对于藻类,非限制性排序和多重比较的结果显示三唑磷在群落层次的影响未达到能够明显区分NOEC_(community)和LOEC_(community)的程度。在单物种层面,在给药后9~12 d,三唑磷对单细胞的羊角月牙藻Selenastrum capricornutum种群有刺激作用。其NOECspecies和LOECspecies分别为1.75μg·L~(-1)和17.5μg·L~(-1)。没有迹象表明三唑磷的引入能够明显改变水体pH、电导、浊度和水体C循环状况。结合暴露评估软件GNEEC(Version 2.0)输出的环境浓度(峰值为2.44μg·L~(-1)),本研究结果显示三唑磷在正常使用剂量下有可能对稻田周边浮游动物群落的内部结构造成扰动,但是它不会对整个系统造成不可恢复的影响。     

水环境中藻毒素生态风险的物种敏感性分布评价

藻毒素对人体的健康风险已受普遍关注,然而其对水生态物种敏感性分布的影响尚不明朗。本研究采集已有实验数据,利用种间相关性分析(ICE)模型和物种敏感性分布评估(SSDs)方法,筛选了64个水生生物物种的71组急性毒性数据(EC50),构建水生生物对肝毒素(节球藻毒素、柱孢藻毒素)和神经毒素(类毒素、贝毒素)的SSD方程。在此基础上,计算不同暴露浓度下的潜在影响比例(PAF)以及保护95%物种基础上藻毒素对水生生物的生态风险阈值(HC5),比较不同类别生物对藻毒素的敏感性以及藻毒素对水生生物的生态风险。结果表明:(1)在95%物种保护保证率下,节球藻毒素、柱孢藻毒素、类毒素和贝毒素对全部物种的HC5值分别为74.96、205.39、194.39、0.3μg·L~(-1),贝毒素水生态风险最高,柱孢藻毒素最低。(2)柱孢藻毒素、类毒素对无脊椎动物的HC5值分别为122.93、95.19μg·L~(-1),低于全部物种的HC5值,无脊椎动物受柱孢藻毒素、类毒素影响较其他物种大。(3)物种潜在影响比例可明确表征敏感性,柱孢藻毒素、类毒素在各浓度暴露情景下对无脊椎动物的PAF值均高于脊椎动物,显示无脊椎动物的敏感性较高。     

Dental caries in fluorine exposure areas in China

In this study, fluorine concentrations in drinking water and in urine of residents from a fluorine exposure area in China were tested. DMFT (average number of decayed, missing and filled teeth) of local residents in four age groups were also determined. The results of the study indicate that in fluorine exposure areas, there is a strictly positive correlation between fluorine content in urine and the fluorine content in drinking water. Effect of dental caries by high fluorine content drinking water is different for the different age groups. High fluorine content drinking water is more dangerous for 15-and 18-year-old groups than 5- and 12-year-old groups.     

Geological factors controlling occurrence and distribution of arsenic in groundwaters from the southern margin of the Duero Basin,Spain

Groundwater from springs and boreholes on the southern edge of the Cenozoic Duero Basin (DB) of Spain has concentrations of arsenic (As) which are commonly above the EC drinking-water limit of 10 μg/L and reach observed values up to 241 μg/L. Groundwater compositions within the sedimentary aquifer vary from Ca–HCO₃ type, variably affected by evaporation and agricultural pollution at shallow levels, to Na–HCO₃ compositions in deeper boreholes of the basin. Groundwater conditions are mainly oxidising, but reducing groundwaters exist in sub-basins within the aquifer, localised flow paths likely being influenced by basement structure. Arsenic concentrations are spatially variable, reaching up to 38 μg/L in springs of the Spanish Central System (SCS) basement aquifer and up to 62 μg/L in springs from the DB. Highest As concentrations are associated with the Na–HCO₃ compositions in deep boreholes (200–450 m depth) within the DB. These have high pH values (up to 9.6) which can give rise to associated elevated concentrations of V and U (up to 64 and 30 μg/L, respectively). In the deep borehole waters of the DB, oxidising flows derived from the mineralised igneous–metamorphic basement and discharging via major faults, and are considered the origin of the higher concentrations. Compositions are consistent with desorption of As and other anionic species from metal oxyhydroxides in an oxic environment. Under locally reducing conditions prevalent in some low-flow parts of the DB, an absence of detectable dissolved As is coincident with low or undetectable SO₄ concentrations, and consistent with loss via formation of authigenic sulphide minerals. Mitigation measures are needed urgently in this semi-arid region where provision of alternative sources of safe drinking water is logistically difficult and expensive.