Imputing Unmeasured Explanatory Variables in Environmental Epidemiology With Application to Health Impact Analysis of Air Pollution

This paper presents the results of a reconsideration of earlier work that finds an association between daily hospital admissions for respiratory distress and daily concentrations of sulphate (lag 1) as well as daily maximum concentrations of ozone (lags 1 and 3). These associations are found even after clustering the data by hospital of admission and accounting for the effects of temperature. We use an adaptation of their generalized estimating equation technique for clustered data, that daily data being for southern Ontario summers from 1983 to 1988. Like them, we adjust for daily maximum temperatures. However, unlike the earlier work returned to ours includes daily average humidity as a potential explanatory variable in our model. Our analysis also differs from theirs in that we cluster the data by census subdivision to reduce the risk of confounding pollutant levels with population size within regions. Moreover, we log-transform the explanatory variables and then high-pass filter the resulting data. We also deviate from the earlier analysis by taking account of measurement error incurred in using surrogate measures of the explanatory variables. To do so we use new methodology designed for our study but of potential value in other applications. That methodology requires a spatial predictive distribution for the unmeasured explanatory variables. Each day about 700 missing measurements for each of these variables can then be imputed over the geographical domain of the study. With these imputations we get a measure of imputation error through the covariance of the predictive distribution. Along with the predictive distribution we require an impact model to link-up with the predictive distribution. We describe that model and show how it uses the imputed measurements of the missing values of the explanatory variables. We also show how through that model, uncertainty about these values is reflected in our analysis and in commensurate uncertainties in the inferences made. Apart from its substantive objectives, our analysis serves to test the new methods with the earlier results serving as a foil. The reassuring qualitative agreement between our findings and the earlier results seems encouraging.     

Passive sampling of PAHs in indoor air in Nepal

PAHs were sampled in ten homes in the Makwanpur region, Nepal. SPMDs and moss bags (Sphagnum girgensohnii) were used as passive samplers. Soot particles on the SPMD surfaces were also analyzed for PAHs. The overall PAH concentrations in SPMDs were significantly higher than those in moss bags. Total PAH mean concentrations of ten houses were 535μg/g lipid for SPMDs and 7.2 μg/g moss (dw) for moss bags. Ratios of phenanthrene/anthracene in indoor SPMDs and particulate matter varied from 2.9 to 3.5 and ratios of fluoranthene/pyrene varied from 1.1 to 1.4. The values for moss bags were respectively 1.7–3.6 and 0.8–2.4. These ratios indicate that the PAHs are from combustion origin. The PAH concentrations in ambient air were estimated as B(a)P TEQs and they were 17–64 times higher than acceptable limit for Finnish community air. Based on PAH levels in the gas phase (SPMD) we may expect PAHs to have an impact on respiratory disease prevalence in Nepalese villages. Both of the sampling methods were feasible in the difficult conditions under which the study was performed.     

重点行业在用呼吸防护用品质量状况的调查分析

调查重点行业企业在用呼吸防护用品质量状况,发现主要问题并研究对策,促进对呼吸防护用品的监督管理。对106家企业进行问卷调查,并随机抽样37家企业对在用69种呼吸防护用品进行检测。所有企业均配发了呼吸防护用品,样品合格率为40.58%,LA认证率33.33%。防尘口罩过滤效率和泄漏率的合格率较低（40.38%和48.08%）,且国内外品牌差异具有统计学意义（P<0.05）;防毒口罩防护时间合格率35.29%,防护时间、过滤元件通气阻力（30 L/Min和95 L/Min）的国内外品牌差异具有统计学意义（P<0.05）。     

Modification of the activated sludge model for chemical dosage

Full-scale experiments have been carried out to adapt the activated sludge model ASM2d to include the influence of metal dosage (Fe³⁺ and Al³⁺) for phosphorus removal. Phosphorus removal rates, nitrification rates, as well as pH and sludge settling performance, were evaluated as functions of the metal dosages. Furthermore, models relating certain parameters to the dosage of chemicals have been derived. Corresponding parameters in the ASM2d and the secondary settler models, included in the Benchmark Simulation Model No 1 (BSM1), have been modified to take the metal influence into consideration. Based on the effluent limits and penalty policy of China, an equivalent evaluation method was derived for the total cost assessment. A large number of 300-day steady-state and 14-day open-loop dynamic simulations were performed to demonstrate the difference in behavior between the original and the modified BSM1. The results show that 1) both in low and high mole concentrations, Fe³⁺ addition results in a higher phosphorus removal rate than Al³⁺; 2) the sludge settling velocity will increase due to the metal addition; 3) the respiration rate of the activated sludge is decreased more by the dosage of Al³⁺ than Fe³⁺; 4) the inhibition of Al³⁺ on the nitrification rate is stronger than that of Fe³⁺; 5) the total operating cost will reach the minimum point for smaller dosages of Fe³⁺, but always increase with Al³⁺ addition.     

模拟电镀污泥重金属浸出液对氧化亚铁硫杆菌活性的影响

从浙江温州某制革厂污泥中筛选到1株细菌,对其形态和16S rDNA序列研究表明,细菌细胞呈杆状,革兰氏染色阴性,其16S rDNA序列与嗜酸性氧化亚铁硫杆菌标准菌株Acidithiobacillus ferrooxidans ATCC23270的序列相似度为99%,可鉴定为嗜酸性氧化亚铁硫杆菌菌株,暂命名为WZ-1.为了研究电镀污泥浸出液中重金属离子对WZ-1活性的影响,考察了Ni2+、Cr3+、Cu2+、Zn2+这4种重金属离子及5种不同模拟电镀污泥重金属浸出液对WZ-1 Fe2+氧化活性和表观呼吸速率的影响,结果表明菌株在接种量6.7%、初始pH 2.0、温度30℃、转速150 r·min-1的条件下,浓度分别为5.0 g·L-1、0.1 g·L-1的Ni2+、Cr3+对WZ-1的活性没有影响;WZ-1对Ni2+、Cr3+、Cu2+、Zn2+的最大耐受浓度分别为:30.0、0.1、2.5、30.0 g·L-1;5种模拟电镀污泥重金属浸出液对WZ-1活性的影响有明显差异,抑制强弱顺序为:Cu/Ni/Cr/Zn>Cu/Ni/Zn>Cu/Cr/Zn>Cu/Ni/Cr>Ni/Cr/Zn.     

用ESR研究香烟烟气对多形核白细胞呼吸爆发的影响

用自旋捕集技术,以二甲基吡咯啉氮酮DMPO(5,5-dimethyl—1-oxide)作为捕捉剂,对吸烟中的气相物质能否刺激人多形核白细胞(PMN)进行呼吸爆发以及吸烟中的气相物质对促癌剂咐(口拜)醇PMA(phorbol myristate acetate)刺激的PMN释放的O_2~-动力学过程的影响进行了研究。结果表明,香烟烟气不能刺激PMN释放O_2~-,但可以改变受PMA刺激的PMN释放O_2~-的动力学过程,且随香烟烟气量的增加,PMN释放出O_2~-的浓度逐渐减小。     

大气气溶胶粒径分布特征与呼吸系统暴露评估研究进展

近年来气溶胶污染被社会各界密切关注.大气气溶胶的粒径分布和污染物组成特征研究是探究大气气溶胶污染成因的基础,同时也是准确评估人体暴露于气溶胶污染导致的健康风险的关键.多级采样器可分粒径采集大气气溶胶,通过模拟人体呼吸系统进而准确量化大气气溶胶组分被吸入后在人体的沉积部位和沉积量,从而被应用至大气气溶胶粒径分布特征和人体健康风险评估的研究中.本文介绍了大气气溶胶粒径分级方法,探讨了应用多级采样器在气溶胶粒径分布研究中存在的主要问题及解决方案,并综述了大气气溶胶粒径分布特征和人体呼吸系统暴露评估的研究进展,最后结合当前的研究现状对大气气溶胶在粒径分级和人体健康风险研究领域的未来发展方向进行了展望.     

儿童呼吸系统疾病对肺功能影响的探讨

通过 1 995～ 1 996年 3次肺功能测量和家庭健康问卷调查发现 ,患过感冒咳嗽、咳痰、气喘、哮喘和支气管炎的儿童中 FEV1 / FVC、FEV1 /预测值以及 FVC/预测值的异常率比未患过这 5种疾病的儿童都高 ,且前者达到显著性水平。FVC/预测值、FEV1 /预测值有部分疾病异常率达到显著水平。患过呼吸系统疾病 ,且肺功能测量异常的儿童比未患过呼吸系统疾病 ,且肺功能测量正常儿童的 FVC调整预测值下降 3 4 5～ 4 1 8ml,FEV1 调整预测值下降 3 56～ 4 75ml,FEV1 /FVC平均下降 1 4 .2 %～ 1 9.4 %。说明曾患过呼吸系统疾病儿童的肺功能已受到了一定程度的影响     

基于氧利用速率表征好氧吸磷过程特性

过程监测及调控是废水生物除磷工艺得以长期稳定运行的基础。为了获取氧利用速率（OUR）在生物除磷过程的潜在应用及该过程氧利用特性,开展聚磷菌好氧吸磷过程的呼吸测量实验,分析了OUR曲线变化与磷酸盐浓度变化、胞内聚合物（PHAs）氧化、外源COD存在与否与浓度变化及pH变化之间的响应关系。研究得到如下结果：富集污泥无磷酸盐存在时,体系依然存在明显的氧利用行为,在不吸磷的情况下聚磷菌胞内的PHAs依然会好氧氧化;外源COD的存在将改变PAOs吸磷速率并延长好氧吸磷的结束时间;体系初始pH的不同导致好氧吸磷效率、吸磷过程pH变化趋势及变化程度的不同;不同的初始条件得到不同的OUR。分析证实,利用测量OUR来监测聚磷菌好氧吸磷过程的运行状态是可行的。     

毒死蜱对紫金山森林土壤酶活力及微生物毒性影响研究

毒死蜱是有机磷类农药,对乙酰胆碱酯酶具有抑制作用,在农业虫害防治中应用广泛。为掌握毒死蜱对森林土壤酶活力和土壤微生物生态效应,选择紫金山森林土作为受试土壤,采用室内培养法,研究了毒死蜱对土壤蔗糖酶、脲酶、酸性磷酸酶和过氧化氢酶,以及土壤呼吸强度和氮素硝化作用的影响。结果表明:试验期间,1.25 mg a.i.·kg-1、12.5 mg a.i.·kg-1和125 mg a.i.·kg-1毒死蜱对土壤脲酶、酸性磷酸酶总体表现为抑制作用;对土壤蔗糖酶和过氧化氢酶的影响与暴露剂量和暴露时间有关,在60 d时,Z1低剂量处理组(1.25 mg a.i.·kg-1)蔗糖酶和过氧化氢酶可恢复,Z100高剂量处理组(125 mg a.i.·kg-1)抑制作用不能解除。试验初期,毒死蜱对土壤呼吸强度有一定刺激作用随后逐渐恢复;对土壤氮硝化作用影响表现为先促进后抑制,且抑制作用有长期影响。由此可知,毒死蜱使用对紫金山森林土的土壤酶活性和土壤微生物产生毒性效应,具有一定生态风险。