Organic and elemental carbon in atmospheric particles

The carbonaceous material, present especially in the respirable atmospheric particulate, is emitted directly from the combustion processes and it is composed of an organic fraction, organic carbon (OC) and of a fraction which is resistant to oxidation at temperatures below approximately 400 degrees C, elemental carbon (EC). In this paper OC and EC concentrations are reported measured in downtown Rome and in a park, Villa Ada, by means of an analyzer which utilizes the thermal properties of the particles. The temporal trends of EC and OC in Rome are in good agreement during the entire period investigated (correlation coefficient between 0.86-0.90). On the other hand the comparison with Villa Ada shows a different contribution from secondary origin pollutants. The carbonaceous fraction in the total particulate mass, measured by means of a TEOM analyzer, varies between 30-40% in downtown and 20-25% in the park, respectively.     

The NAS perchlorate review: questions remain about the perchlorate RfD

Human exposure to perchlorate is commonplace because it is a contaminant of drinking water, certain foods, and breast milk. The U.S. Environmental Protection Agency (EPA) conducted a perchlorate risk assessment in 2002 that yielded a reference dose (RfD) based on both the animal and human toxicology data. This assessment has been superceded by a recent National Academy of Science (NAS) review that derived a perchlorate RfD that is 20-fold greater (less stringent) than that derived by the U.S. EPA in 2002. The NAS-derived RfD was put on the U.S. EPA's Integrated Risk Information System (IRIS) database very quickly and with no further public review. In this commentary we raise concerns about the NAS approach to RfD development in three areas of toxicity assessment: the dose that the NAS described as a no observable adverse-effect level is actually associated with perchlorate-induced effects; consideration of uncertainties was insufficient; and the NAS considered the inhibition of iodine uptake to be a nonadverse effect. We conclude that risk assessors should carefully evaluate whether the IRIS RfD is the most appropriate value for assessing perchlorate risk.     

快速二氧化碳结合力测定器的研制

介绍了一种测定二氧化碳结合力的新型仪器.根据ISO15189实验室认可的要求,对该测定器性能进行评价.结果表明,该测定器安全无污染,测定结果准确,具有一定的实用性.     

Uptake of perchlorate in terrestrial plants

Cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.), and soybean (Glycine max) were used to determine uptake of the perchlorate anion (100 ppb) from sand. Plants were watered with different ratios of Hydrosol (a diluted solution of Peters All-Purpose Plant Food) to Milli-Q water (18 MOmega) to determine if the presence of other nutrients (such as nitrate) influenced perchlorate uptake. Perchlorate concentrations in sand and plant tissues were determined weekly. Perchlorate uptake was observed in all three plant species. In most experiments, perchlorate was completely depleted from sand in which plants were growing. Perchlorate concentrations in lettuce were also significantly higher than those in cucumber and soybean (P < 0.0001). Perchlorate concentrations in sand decreased at a higher rate at lower ratios of Hydrosol to Milli-Q, indicating that plant (cucumber) uptake of perchlorate is influenced by the presence of external nutrients. The results of an 8-week uptake study in cucumber and a 6-week uptake study in lettuce suggest that a threshold perchlorate concentration is reached: for cucumber, 150 ppm and for lettuce, 750 ppm. Although the presence of external nutrients decreases the rate of perchlorate uptake by plants, significant concentrations of perchlorate occur in aboveground plant tissues even after relatively short periods of growth. The potential for trophic transfer of perchlorate from soil to higher organisms through plants exists.     

Reduction of perchlorate in river sediment

The transformation of perchlorate was investigated in river sediment during laboratory batch and column studies to determine if reduction of perchlorate is a viable pathway in natural sediment without previous exposure to perchlorate. Perchlorate at an initial concentration of 10 microM was reduced quantitatively to chloride in 3 d after a lag phase of 2 d in sediment slurries amended with lactate. Raising the initial concentration of perchlorate to 1,000 microM increased the lag phase to 20 d before reduction occurred. At perchlorate concentrations greater than 1,000 microM, the reduction of perchlorate was not observed within 40 d. We speculate that the high concentration of perchlorate specifically was problematic to the microbes mediating the reduction of perchlorate. High levels of nitrate inhibited the reduction of perchlorate as well. In sediment slurries amended with 870 microM sodium nitrate, the reduction of perchlorate at an initial concentration of 100 microM did not occur before day 15 of the experiment, but complete removal of nitrate had occurred by day four. Sediment column studies further demonstrated the dependence of perchlorate reduction on endogenous nitrate levels.     

Novel biomarkers of perchlorate exposure in zebrafish

Perchlorate inhibits iodide uptake by thyroid follicles and lowers thyroid hormone production. Although several effects of perchlorate on the thyroid system have been reported, the utility of these pathologies as markers of environmental perchlorate exposures has not been adequately assessed. The present study examined time-course and concentration-dependent effects of perchlorate on thyroid follicle hypertrophy, colloid depletion, and angiogenesis; alterations in whole-body thyroxine (T4) levels; and somatic growth and condition factor of subadult and adult zebrafish. Changes in the intensity of the colloidal T4 ring previously observed in zebrafish also were examined immunohistochemically. Three-month-old zebrafish were exposed to ammonium perchlorate at measured perchlorate concentrations of 0, 11, 90, 1,131, and 11,480 ppb for 12 weeks and allowed to recover in clean water for 12 weeks. At two weeks of exposure, the lowest-observed-effective concentrations (LOECs) of perchlorate that induced angiogenesis and depressed the intensity of colloidal T4 ring were 90 and 1,131 ppb, respectively; other parameters were not affected (whole-body T4 was not determined at this time). At 12 weeks of exposure, LOECs for colloid depletion, hypertrophy, angiogenesis, and colloidal T4 ring were 11,480, 1,131, 90, and 11 ppb, respectively. All changes were reversible, but residual effects on angiogenesis and colloidal T4 ring intensity were still present after 12 weeks of recovery (LOEC, 11,480 ppb). Whole-body T4 concentration, body growth (length and weight), and condition factor were not affected by perchlorate. The sensitivity and longevity of changes in colloidal T4 ring intensity and angiogenesis suggest their usefulness as novel markers of perchlorate exposure. The 12-week LOEC for colloidal T4 ring is the lowest reported for any perchlorate biomarker in aquatic vertebrates.     

高氯酸盐的环境毒理学效应及其机制的研究进展

高氯酸盐是一种具有持久性的有毒污染物质,其环境污染问题引起了人类的广泛关注.天然环境中的高氯酸盐比例很少,主要存在于土壤中;此外,在某些环境条件下,大气中也能产生一定量的高氯酸盐;其人为污染主要来源于大量生产和使用的高氯酸铵和高氯酸钾.高氯酸盐易溶于水,可以在水环境中快速迁移扩散,在动植物体内富集并通过人类摄食作用进入人体.高氯酸根能够竞争性利用钠/碘转运体(NIS),抑制甲状腺吸收碘离子,进而影响甲状腺和脑垂体的激素水平,阻碍生物体正常的新陈代谢和生长发育.笔者基于高氯酸盐对甲状腺、生长发育、生殖行为及神经系统等潜在危害的毒理学研究,综述了高氯酸盐对生物体的毒性作用机制,并对其研究前景进行了展望.     

过氯酸铵对家兔的毒作用影响

目的 研究过氯酸铵(AP)对家兔的毒作用影响,为其应用和防护提供毒理学依据.方法 选用家兔25只,随机分为低、中、高剂量组(AP 22.5、45.0、90.0 mg/kg)、对照组(生理盐水)和博来霉素(BLM A5)组(4 mg/只).经气管每周染毒1次并称体重,染毒13周,于第23周进行耳缘采血并处死.解剖取各脏器称重,计算各脏器指数.检测血常规、血清生化及甲状腺激素指标.结果 染毒至第8、11、12周,高剂量组和BLM A5组家兔体重均比对照组明显降低,差异有统讣学意义(P＜0.05).BLMA5组肺脏器指数(5.05‰)比对照组及低、中剂量组(3.32‰、3.94‰、3.58‰)明显升高,差异有统计学意义(P＜0.05或P＜0.01).中、高剂量组WBC计数明显低于低剂量组,差异有统计学意义(P＜0.05);低、中剂量组及BLM A5组:RBC计数均低于对照组,差异有统计学意义(P＜0.05或P＜0.01).高剂量组羟脯氨酸(HYP)含量(26.5μg/ml)明显高于对照组,差异有统计学意义(P＜0.05).血清FT3有随染毒剂量升高的趋势;高剂量组FT4(19.76 pmol/L)明显高于对照组和低剂量组,差异有统计学意义(P＜0.05或P＜0.01).结论 肺脏器系数有随AP染毒剂量增加而升高的趋势;AP对WBC和RBC未见明显毒作用影响;在AP停止染毒的第10周,血清FT3、FT4升高,其变化与AP染毒剂量大小趋向一致,可能与甲状腺功能的反馈性调节有关,但还需进一步证实.     

Development of freshwater water-quality criteria for perchlorate

The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for rockets and missiles; in explosives, flares, fireworks, chemical processes, and automobile air-bag inflators; and for other assorted uses. With recent advances in analytical detection capability, perchlorate has been found in a variety of ground and surface waters throughout the United States. Because perchlorate has been associated with thyroid problems in humans and may have similar effects on wildlife, it is desirable to develop a water-quality criterion to assist in identifying concentrations of perchlorate in water likely to pose an ecological health risk. In the present study, we compiled all available data regarding the effects of perchlorate to aquatic organisms, and we performed additional toxicity and bioconcentration tests as required by the U.S. Environmental Protection Agency (U.S. EPA) for the development of water-quality criteria for aquatic life. A criterion maximum concentration of 20 mg/L and a criterion continuous concentration of 9.3 mg/L were calculated based on the test results. Although these are not formal Clean Water Act Section 304(a) criteria, which must be published by the U.S. EPA, these criteria may be useful in the determination of remedial action levels for contaminated sites, for National Pollutant Discharge Elimination System permit limits, and other water-quality management practices.     

过氯酸铵对大鼠甲状腺的毒作用

目的　研究过氯酸铵 (AP)对甲状腺的毒作用影响。方法　用Wistar大鼠 88只 ,随机分为 4组 ,分别经口染毒 13周和 36周。染毒 13周 ,3个组AP剂量分别为 12 9、2 5 7、5 14mg·kg-1·d-1,1个对照组则饮水 ;染毒 36周 ,3个组AP剂量分别为 1.2、4 6 .5、4 6 5 .0mg·kg-1·d-1,1个对照组则饮水。观察大鼠活动表现及体重变化 ,检测血清中甲状腺激素水平及观察其病理改变。结果　不同时间AP染毒后大鼠活动未见异常 ,体重增长亦无明显差异。染毒 13周 ,5 14mg组游离三碘甲状腺原氨酸(FT3 2 .4 8pmol/L)、游离甲状腺素 (FT413.33pmol/L)均低于对照组 (3.2 4、2 0 .92pmol/L) ,促甲状腺激素 (TSH 0 .38mIU/L)、甲状腺球蛋白 (TG 3.37μg/L)均高于对照组 (0 .2 9mIU/L、2 .0 0μg/L) ,差异均有显著性 (P <0 .0 5 ) ;其他组各指标差异均无显著性 (P >0 .0 5 ) ;染毒 36周 ,4 6 5mg组FT3 (2 .6 5pmol/L)明显低于对照组 (4.97pmol/L) ,差异有显著性 (P <0 .0 1) ;4 6 .5、4 6 5mg组FT4(10 .6 3、2 .17pmol/L)明显低于对照组 (15 .74pmol/L) ,差异有显著性 (P <0 .0 5 ,P <0 .0 1) ;4 6 5mg组TSH(0 .34mIU/L)与对照组 (0 .14mIU/L)比较 ,差异有显著性 (P <0 .0 5 ) ;1.2mg组各指标均未见明显损害变化。镜检 1.2mg组甲     

Benchmark calculations for perchlorate from three human cohorts

The presence of low concentrations of perchlorate in some drinking water sources has led to concern regarding potential effects on the thyroid. In a recently published report, the National Academy of Sciences indicated that the perchlorate dose required to cause hypothyroidism in adults would probably be > 0.40 mg/kg-day for months or longer. In this study, we calculated benchmark doses for perchlorate from thyroid-stimulating hormone (TSH) and free thyroxine (T4) serum indicators from two occupational cohorts with long-term exposure to perchlorate, and from a clinical study of volunteers exposed to perchlorate for 2 weeks. The benchmark dose for a particular serum indicator was defined as the dose predicted to cause an additional 5 or 10% of persons to have a serum measurement outside of the normal range. Using the data from the clinical study, we estimated the half-life of perchlorate in serum at 7.5 hr and the volume of distribution at 0.34 L/kg. Using these estimates and measurements of perchlorate in serum or urine, doses in the occupational cohorts were estimated and used in benchmark calculations. Because none of the three studies found a significant effect of perchlorate on TSH or free T4, all of the benchmark dose estimates were indistinguishable from infinity. The lower 95% statistical confidence limits on benchmark doses estimated from a combined analysis of the two occupational studies ranged from 0.21 to 0.56 mg/kg-day for free T4 index and from 0.36 to 0.92 mg/kg-day for TSH. Corresponding estimates from the short-term clinical study were within these ranges.     

Neonatal thyroxine level and perchlorate in drinking water

Environmental contamination of drinking water has been observed for perchlorate, a chemical able to affect thyroid function. This study examines whether that exposure affected the thyroid function of newborns. Neonatal blood thyroxine (T4) levels for days 1 to 4 of life were compared for newborns from the city of Las Vegas, Nevada, which has perchlorate in its drinking water, and those from the city of Reno, Nevada, which does not (detection limit, 4 micrograms/L [ppb]). This study is based on blood T4 analyses from more than 23,000 newborns in these two cities during the period April 1998 through June 1999. No difference was found in the mean blood T4 levels of the newborns from these two cities. Drinking water perchlorate levels measured monthly for Las Vegas ranged during this study period from non-detectable for 8 months to levels of 9 to 15 ppb for 7 months. Temporal differences in mean T4 level were noted in both cities but were unrelated to the perchlorate exposure. This study was sufficiently sensitive to detect the effects of gender, birth weight, and the day of life on which the blood sample was taken on the neonatal T4 level, but it detected no effect from environmental exposures to perchlorate that ranged up to 15 micrograms/L (ppb).     

离子色谱法测定饮用水中高氯酸盐含量研究

目的:建立一种简便快速梯度淋洗离子色谱法测定饮用水中高氯酸盐含量。方法:选用以高容量、强亲水性IonPac AS23阴离子分析柱,0 mmol/L~40 mmol/LKOH淋洗液,流速为1.0 m l/m in,电导检测器,样品经0.45μm滤膜过滤后直接进样。结果:本法相关性好(r=0.9998),相对标准偏差(RSD)为2.15%~5.99%,样品加标平均回收率为87.9%~101%,最低检出量为3.0μg/L。结论:该法操作简单、快速、准确、灵敏、适用于大批水样分析。