2019年西宁市城区PM2.5中重金属污染特征及健康风险评价

目的 分析西宁市城区PM2.5中重金属的污染水平，并对其健康风险进行评价。方法 2019年每月10-16日在西宁市城区2个监测点采集PM2.5样品，分析其中砷、镉、铬、镍、铅、汞、锰7种重金属的含量和污染特征，用健康风险评价模型对重金属进行呼吸暴露健康风险评价。结果 2019年1月至12月西宁市城区2个监测点PM2.5中7种重金属元素的年均浓度范围为2.50×10-8～3.38×10-5 mg/m³，由高到低依次为铅>锰>砷>铬>镍>镉>汞，2个监测点PM2. 5中铅、镉、汞、砷的年均浓度低于GB3095-2012《环境空气质量标准》标准限值,富集因子均小于10。PM2. 5中重金属对人群的超额危险度为6.73×10-13～1.40×10-7，致癌金属的超额危险度由高到低依次为铬>砷>镉>镍，非致癌金属的超额危险度依次为铅>锰>汞，砷、镉、铬、镍的终生致癌超额危险度均低于人群可接受的危险度水平（10-6）。结论 西宁市城区PM2. 5中重金属主要来自自然源，其中铬对人体健康的年均超额危险度较高，应密切关注。     

北京和阿拉善盟沙尘天气PM10和PM2.5中化学元素含量变化的研究

目的探讨北京地区沙尘暴期间PM10、PM2.5中所含化学元素含量变化的规律和特点。方法 2007年5—6月连续30d监测PM10、PM2.5浓度,每天24h连续采样,利用采样前后质量差值的差重法计算每日PM10、PM2.5的日均质量浓度。采用原子吸收光谱法,X-荧光分析法和电感耦合等离子体质谱法(ICP-MS)测量颗粒物的金属元素。气象数据由当地气象局提供。结果北京市大气PM2.5中铝、锰、锶、钛、镍、钙、硅、铁、镁元素含量,PM10中铝、锰、钛、钙、硅、铁、镁元素含量低于阿拉善盟。北京市大气PM2.5中铜、锌、铅、砷、镐、钼、镉、钾、硼元素含量,PM10中铜、锌、铅、砷、镐、钼、镉、钾、钡、汞元素含量高于阿拉善盟。阿拉善盟地区沙尘天气大气PM2.5中镐、钼、镉、汞、铅、铜、锌元素含量,PM10中镐、钼、镉、汞、铅、硼元素含量,与非沙尘天气比较,差异没有统计学意义。其他元素含量在沙尘天气时出现浓度增高的现象,差异有统计学意义。北京地区沙尘天气PM2.5中铝、磷、锰、锶、钡、钛、镍、钙、硅、铁、镁、钠、镐、硼元素含量升高;沙尘天气PM10中铝、磷、锰、锶、钡、镍、钙、硅、铁、镁、钠、镐、硼、钛元素含量升高。沙尘天气时PM2.5和PM10中锌、铅、砷、镉、汞、铜元素含量降低。沙尘天气PM2.5和PM10中钼、钾元素含量与非沙尘天气比较,变化并不明显。结论北京出现沙尘天气时,对汽车尾气带来的锌、铅、铜3种元素的污染有一定的稀释和缓解作用。     

2015年兰州市大气细颗粒物成分监测

目的 了解兰州市大气细颗粒物(PM2.5)含量及成分,为大气污染源解析提供依据.方法 于2015年1-12月分别在兰州市城关区和西固区各1个监测点采集大气PM2.5样品84份,分析样品中PM2.5质量浓度及PM2.5中无机水溶性离子、金属元素、多环芳烃含量.结果 城关区大气PM2.5平均质量浓度高于西固区(Z=-3.226,P＜0.01);西固区大气PM2.5中NO3-质量浓度低于城关区,PM2.5中锑、铍、铬的质量浓度高于城关区,镉、汞、铅、锰、镍的质量浓度低于城关区,差异均有统计学意义(P＜0.05);城关区大气PM2.5中16种多环芳烃均值为1.15 ng/m3,西固区大气PM2.5中16种多环芳烃均值为0.95 ng/m3,城关区高于西固区,差异有统计学意义(P＜0.05).结论 2015年兰州市城关区和西固区大气PM2.5污染水平及主要污染成分不同,需有针对性地制定大气污染防控措施.     

焦化作业环境空气中颗粒物的污染特征研究

目的 了解焦化作业环境空气中颗粒物的污染特征,为制定焦炉逸散物职业接触限值提供科学依据.方法 选取武汉市某焦化厂的附属、炉底、炉侧和炉顶作业区,测定一氧化碳(CO)、二氧化硫(SO2)、苯可溶物(BSM)、苯系物(包括苯、甲苯和二甲苯)、PM10、PM2.5,PM10和PM2.5上16种多环芳烃(PAHs)浓度,分析颗粒物与颗粒物上载带PAHs、BSM以及焦炉逸散物其他组分的关系.结果 焦化作业区空气中CO、SO2、BSM、苯系物、PM10和PM2.5及它们载带总PAHs浓度呈现附属＜炉底＜炉侧＜炉顶的趋势,趋势有统计学意义(P趋势＜0.05).PM2.5,占PM10的比例在焦化作业区间差异无统计学意义(P＞0.05).PM10与CO、SO2、苯、苯系物和BSM呈正相关,相关系数分别为0.705、0.823、0.664、0.624和0.734(P＜0.05);PM2.5与CO、SO2、苯、苯系物和BSM呈正相关,相关系数分别为0.635、0.916、0.680、0.553和0.726(P＜0.05);BSM与苯呈正相关,相关系数为0.698(P＜0.05).PM10和PM2.5上PAHs的环数分布在各作业区相同.各作业区空气中PM10和PM2.5上PAHs的总苯并(a)芘等当量浓度中位数的差异无统计学意义(P＞0.05).结论 焦化厂空气中颗粒物浓度与焦炉逸散物中其他组分相关,单位体积空气中PM10和PM2.5上PAHs的含量和种类相似.     

某市秋冬季大气PM_(2.5)中金属元素的健康风险评价

[目的]分析某市秋冬季大气PM_(2.5)中金属元素的污染特征,并对其健康风险进行评价。[方法]采集该市2016年9—10月(秋季)和2016年12月—2017年1月(冬季)PM_(2.5)样品,采用电感耦合等离子体质谱法分析其中的锑、铝、砷、铍、镉、铬、汞、铅、锰、镍、硒、铊12种元素的含量。利用富集因子法和健康风险指数法对其中7种元素(镉、铅、砷、镍、锰、汞、铬)的危害进行评价。[结果]该市大气PM_(2.5)中12种金属元素含量,秋季为铝锰铅铬砷硒镍汞锑=镉铊铍;冬季为铝铅锰铊铬砷硒锑汞镉镍铍。除了镍和铍,其余元素的含量均为冬季秋季。富集程度分析显示,秋冬两季PM_(2.5)中汞的富集因子均大于2,属于中度富集,2级污染。镉、铅、砷、镍、锰、铬的富集因子均小于1,无富集。致癌金属元素铬、镍、镉、砷通过呼吸途径对暴露人群的年均超额危险度为2.73×10-9~2.02×10~(-6)。非致癌金属元素铅、汞、锰的年均超额危险度为1.20×10~(-10)~1.41×10~(-9)。7种金属元素对不同人群年均超额危险度为:成年男性1.33×10-10~2.02×10-6;成年女性1.20×10-10~1.82×10~(-6);儿童1.20×10~(-10)~1.09×10~(-6)。[结论]某市秋冬季大气PM_(2.5)中,除镍和铍外,金属元素呈现冬季秋季的趋势。     

可吸入颗粒物PM_(2.5)的影响因子分析

运用相关性分析得出了PM2.5与PM10、CO、NO2、SO24项影响因素的相关性,采用多元线性回归方法得到了PM2.5和PM10、CO、NO2和SO2之间的线性回归方程,运用主成分分析方法进行因子分析,结果表明PM2.5与PM10、CO、SO2、NO2呈正相关性。     

汽油车排出颗粒物的化学组分分析

目的 为了进一步了解汽油车尾气颗粒物的化学成分。方法 运用高效液相色谱法测定了尾气颗粒物有机提取物中6种多环芳烃含量,运用原子吸收分光光度法测定了尾气颗粒物无机提取物中5种重金属含量。结果 有提取物中6种多环芳烃按含量高低依次为：苯并（a)芘＞菲＞晕苯＞苯并（a)蒽＞Qu＋芘,其中苯并（a)芘含量占40％。无机提取物中5种重金属按含量高低依次为：铅＞镍＞铬＞镉＞锰,其中铅含量占37％。结论 汽油车尾气颗粒物含量较多的组分是苯并（a）芘和铅。     

南通市大气PM2.5中重金属污染特征及其吸入健康风险评价

目的 了解南通市大气PM2.5中重金属的浓度及其来源,评价重金属的人群健康风险。方法 于2017年和2018年每月10 - 16日在港闸区监测点进行PM2.5采样,共采集样品168份,监测其质量浓度,并采用电感耦合等离子质谱仪（ICP - MS）分析其12种元素的含量,利用富集因子法和主成分分析法识别元素的来源,并对人群进行呼吸暴露健康风险评价。结果 南通市2018年PM2.5中锑、铝、砷、铬、铅、镍、硒、铊浓度均低于2017年,差异有统计学意义(t锑 = 2.36,P＜0.05;t铝 = 5.68,P＜0.05;t砷 = 3.50,P＜0.05 ;t铬 = 2.77,P＜0.05;t铅 = 3.52,P＜0.05;t镍 = 2.03,P＜0.05;t硒 = 3.06,P＜0.05; t铊 = 3.81,P＜0.05);重金属的富集因子（EF）高于10的元素有铍、锑、砷、镉、汞、铅、硒、铊。主成分分析表明南通市PM2.5元素主要来源于工业、交通和自然来源的混合污染等。铅、锰通过呼吸暴露的非致癌风险（HQ）均小于1,砷、铬、镉等元素致癌风险均低于10 - 5。结论 南通大气中重金属污染为复合污染,应从源头治理,从而保护公众健康。     

2019年西安市两城区PM2.5中多环芳烃污染状况及来源分析

目的 调查西安市两城区大气PM2.5中多环芳烃（PAHs）的污染状况,探讨其污染特征及其主要污染来源。方法 2019年每月10—16日和遇到雾霾天气（AQI>200）连续在西安市雁塔区和莲湖区两个监测点采集大气PM2.5样品,按照HJ 647—2013（《环境空气和废气 气相和颗粒物中 多环芳烃的测定 高效液相色谱法》）检测样品中多环芳烃的含量,采用因子分析法对其主要污染来源进行分析。结果 西安市两个主城区PM2.5质量浓度的中位数为0.053mg/m³,低于国家环境空气质量二级标准,超标率为40.50%（81/200）,莲湖区、雁塔区PM2.5质量浓度中位数分别为0.054mg/m³、0.046mg/m³,超标率分别为42.16%（43/102）、38.78%（38/98）,两个地区间的差异无统计学意义（Z=-1.369,P=0.171）。冬季PM2.5质量浓度最高（0.091mg/m³）,夏季PM2.5质量浓度最低,（0.026mg/m³）,不同季节PM2.5质量浓度存在统计学差异（Z=113.949,P<0.001）。莲湖区PM2.5中多环芳烃含量最高的是苯并［g,h,i］苝,其次是茚并［1,2,3-cd］芘、苯并［b］荧蒽,雁塔区PM2.5中多环芳烃含量最高的是荧蒽、芘、茚并［1,2,3-cd］芘,两个地区多环芳烃各成分差异无统计学意义。因子分析法显示西安市PM2.5中多环芳烃的主要来源是汽车尾气（莲湖区、雁塔区贡献率分别为65.32%、61.38%）、燃煤（莲湖区、雁塔区贡献率分别为9.92%、9.34%）、工业来源（莲湖区、雁塔区贡献率分别为7.92%、8.20%）。结论 2019年西安市大气PM2.5超标较严重,主要污染来源于汽车尾气、燃煤和工业来源的混合型污染。     

深圳市罗湖区35户住宅室内环境检测结果分析

目的 了解城市室内环境状况,发现室内环境健康危害因素。方法 分别于2018年夏季和2019年冬季对35户住宅进行室内危害因素检测,采样方法、布点原则及评价参照《室内空气质量标准》（GB/T 18883 - 2002）进行。结果 室内PM10、CO、CO2、NO2、甲醛、苯、甲苯、二甲苯浓度均在标准限值内,配对资料的t检验分析显示冬夏两季室内PM2.5、PM10、CO2、NO2、甲醛浓度差异有统计学意义（PM2.5:t = - 7.151,PM10:t = - 6.693, CO2:t = -3.970,NO2:t = - 4.479,甲醛 t = 2.953, P＜0.05）,其中冬季室内PM2.5、PM10、CO2、NO2总体浓度高于夏季,夏季室内甲醛浓度高于冬季。Pearson相关分析显示室内空气中真菌总数与湿度存在正相关关系（r = 0.244,P＜0.05）,真菌总数与PM2.5呈负相关关系（r = - 0.183,P＜0.05）。结论 深圳市城区室内PM10、CO、CO2、NO2、甲醛、苯、甲苯、二甲苯浓度均在标准限值内,仍需进一步关注室内微生物因素对健康的危害。     

Relationships between air pollution and preterm birth in California

Air pollution from vehicular emissions and other combustion sources is related to cardiovascular and respiratory outcomes. However, few studies have investigated the relationship between air pollution and preterm birth, a primary cause of infant mortality and morbidity. This analysis examined the effect of fine particulate matter (PM(2.5)) and carbon monoxide (CO) on preterm birth in a matched case-control study. PM(2.5) and CO monitoring data from the California Air Resources Board were linked to California birth certificate data for singletons born in 1999-2000. Each birth was mapped to the closest PM monitor within 5 miles of the home address. County-level CO measures were utilised to increase sample size and maintain a representative population. After exclusion of implausible birthweight-gestation combinations, preterm birth was defined as birth occurring between 24 and 36 weeks' gestation. Each of the 10 673 preterm cases was matched to three controls of term (39-44 weeks) gestation with a similar date of last menstrual period. Based on the case's gestational age, CO and PM(2.5) exposures were calculated for total pregnancy, first month of pregnancy, and last 2 weeks of pregnancy. Exposures were divided into quartiles; the lowest quartile was the reference. Because of the matched design, conditional logistic regression was used to adjust for maternal race/ethnicity, age, parity, marital status and education. High total pregnancy PM(2.5) exposure was associated with a small effect on preterm birth, after adjustment for maternal factors (adjusted odds ratio [AOR] = 1.15, [95% CI 1.07, 1.24]). The odds ratio did not change after adjustment for CO. Results were similar for PM(2.5) exposure during the first month of pregnancy (AOR = 1.21, 95% CI [1.12, 1.30]) and the last 2 weeks of pregnancy (AOR = 1.17, 95% CI [1.09, 1.27]). Conversely, CO exposure at any time during pregnancy was not associated with preterm birth (AORs from 0.95 to 1.00). Maternal exposure to PM(2.5), but not CO, is associated with preterm birth. This analysis did not show differences by timing of exposure, although more detailed examination may be needed.     

Associations between air pollution and mortality in Phoenix, 1995-1997

We evaluated the association between mortality outcomes in elderly individuals and particulate matter (PM) of varying aerodynamic diameters (in micrometers) [PM(10), PM(2.5), and PM(CF )(PM(10) minus PM(2.5))], and selected particulate and gaseous phase pollutants in Phoenix, Arizona, using 3 years of daily data (1995-1997). Although source apportionment and epidemiologic methods have been previously combined to investigate the effects of air pollution on mortality, this is the first study to use detailed PM composition data in a time-series analysis of mortality. Phoenix is in the arid Southwest and has approximately 1 million residents (9. 7% of the residents are > 65 years of age). PM data were obtained from the U.S. Environmental Protection Agency (EPA) National Exposure Research Laboratory Platform in central Phoenix. We obtained gaseous pollutant data, specifically carbon monoxide, nitrogen dioxide, ozone, and sulfur dioxide data, from the EPA Aerometric Information Retrieval System Database. We used Poisson regression analysis to evaluate the associations between air pollution and nonaccidental mortality and cardiovascular mortality. Total mortality was significantly associated with CO and NO(2) (p < 0.05) and weakly associated with SO(2), PM(10), and PM(CF) (p < 0. 10). Cardiovascular mortality was significantly associated with CO, NO(2), SO(2), PM(2.5), PM(10), PM(CF) (p < 0.05), and elemental carbon. Factor analysis revealed that both combustion-related pollutants and secondary aerosols (sulfates) were associated with cardiovascular mortality.     

番茄红素对大气可吸入颗粒物致人肺成纤维细胞DNA损伤的保护作用

[目的]探讨大气粗颗粒物(PM10)、细颗粒物(PM2.5)对人肺成纤维细胞(HLF)增殖作用的影响和DNA链的损伤作用以及番茄红素的保护作用.[方法]采用细胞增殖试验(MTT)测定PM10、PM25以及番茄红素对HLF增殖作用.单细胞凝胶电泳法(SCGE)检测PM10、PM25对HLF DNA的损伤程度以及番茄红素对DNA损伤的保护作用.[结果]PM10、PM25均能抑制HLF的增殖,当颗粒物质量浓度为50μg/mL时,HLF的细胞存活率下降约10%,随着染毒剂量的增大细胞存活率进一步下降,具有明显的剂量一效应关系(P<0.01).同样质量浓度下比较,PM25对细胞增殖的抑制作用大干PM10;PM10和PM25均具有明显的DNA损伤作用,当PMs质量浓度仅为50μg/mL时,即能够引起细胞DNA损伤(P<0.01).且具有明显的剂量-反应关系(P<0.01),但PM25的损伤程度小于PM10;番茄红素可以有效地阻止由PM10、PM25导致的DNA损伤,浓度为25μmol/L的番茄红素即可明显减轻PMs对HLF造成的DNA损伤.[结论]PMs能抑制HLF的增殖、诱导HLF的DNA链断裂,番茄红素可以有效地减小PMs对HLF DNA造成的损伤.     

上海市宝山区空气中PM_(10)和PM_(2.5)污染状况分析

[目的]了解上海市宝山区空气中颗粒物PM10和PM2.5的污染水平,为PM2.5污染防治提供参考。[方法]2007年选择钢研所和罗泾监测点分别作为污染区和对照区,采用称重法进行PM10、PM2.5浓度测定。[结果]宝山区空气中PM10、PM2.5年平均浓度分别0.102mg/m3和0.054 mg/m3;冬春季节浓度高于夏秋季;钢研所监测点浓度高于罗泾监测点浓度;PM2.5占PM10的比值为0.55。[结论]上海宝山区空气中颗粒物污染较严重,存在明显季节变化和地区差异。PM2.5在PM10的比例已超半,应重视细颗粒物的空气污染和健康危害。     

Associations between personal exposures and fixed-site ambient measurements of fine particulate matter, nitrogen dioxide, and carbon monoxide in Toronto, Canada

A longitudinal study investigating personal exposures to PM(2.5), nitrogen dioxide (NO(2)), and carbon monoxide (CO) for cardiac compromised individuals was conducted in Toronto, Canada. The aim of the study was (1) to examine the distribution of exposures to PM(2.5), NO(2), and CO; and (2) to investigate the relationship between personal exposures and fixed-site ambient measurements of PM(2.5), NO(2), and CO. In total, 28 subjects with coronary artery disease wore the Rupprecht & Patashnick ChemPass Personal Sampling System one day a week for a maximum of 10 weeks. The mean (SD) personal exposures were 22 microg m(-3) (42), 14 p.p.b. (6), and 1.4 p.p.m (0.5) for PM(2.5), NO(2), and CO, respectively. PM(2.5) and CO personal exposures were greater than central fixed-site ambient measurements, while the reverse pattern was observed for NO(2). Ambient PM(2.5) and NO(2) were correlated with personal exposures to PM(2.5) and NO(2) with median Spearman's correlation coefficients of 0.69 and 0.57, respectively. The correlations between personal exposures and ambient measurements made closest to the subjects' homes or the average of all stations within the study were not stronger than the correlation between personal exposures and central fixed-site measurements. Personal exposures to PM(2.5) were correlated with personal exposures to NO(2) (median Spearman's correlation coefficient of 0.43). This study suggests that central fixed-site measurements of PM(2.5) and NO(2) may be treated as surrogates for personal exposures to PM(2.5) and NO(2) in epidemiological studies, and that NO(2) is a potential confounder of PM(2.5).     

公路收费站作业环境有害因素的监测与分析

目的 监测与评价公路收费站作业环境状况,为加强收费站工作人员的个人防护和职业健康监护提供科学依据.方法 采用GB 3095-96环境空气质量标准、GBZ 1-2002工业企业设计卫生标准、GBZ 2-2002工作场所有害因素职业接触限值等标准检测和采样规范中的方法,对某省内10个收费站亭内外作业环境因素进行监测与分析.结果 收费站车流量为 835-2734辆/h,车型以货车和客车为主;收费亭内外作业环境空气中CO、NO2、SO2、Pb、TSP和PM10的浓度均超过<环境空气质量标准(GB 3095-96)>中二级标准;国道收费站作业环境空气中CO、NO2和SO2的浓度明显高于省道收费站;空气中Pb、TSP和PM10的浓度,省道收费站高于国道收费站;收费亭内外的交通噪声强度分别为(83.4±2.5)和(89.6±3.1)dB(A),等效声级分别为(78.4±2.5)和(82.9±2.6)LAeq dB(A),频谱特性为高、中、低频率均有的非稳态噪声,超过国家规定交通干线两侧,每小时车流量在100辆以上的公路昼间标准70 Leq dB(A);收费亭内外振动强度(ahw)分别为(4.5±1.7)和(3.4±1.4)m/s2,收费亭内高于亭外.结论 公路收费站作业环境较差,受多种有害因素的作用和污染,建议应加强个人防护和职业健康监护.     

沙尘暴细颗粒物致大鼠肺泡巨噬细胞DNA损伤

[目的]探讨沙尘暴和正常天气细颗粒物(PM2.5)及其水提取物和有机提取物对大鼠肺泡巨噬细胞的细胞毒性和DNA的损伤作用。[方法]沙尘暴和正常天气PM2.5于2004年3月采集自甘肃省武威市和内蒙古自治区包头市。细胞毒性用四甲基偶氮唑盐(MTT)分析法观察,细胞DNA损伤用单细胞凝胶电泳(SCGE)技术检测。[结果]沙尘暴和正常天气PM2.5及其水提取物和有机提取物均对大鼠肺泡巨噬细胞产生一定的细胞毒性,且随剂量的增大而增强;然而,沙尘暴与正常天气之间除了包头沙尘暴PM2.5有机提取物之外,余差异均无显著性。正常天气PM2.5和沙尘暴PM2.5水提取物和有机提取物均可引起细胞DNA损伤,且随剂量增加而损伤增大;正常天气PM2.5比沙尘暴PM2.5水提取物和有机提取物对细胞DNA损伤作用更大。不论正常天气PM2.5还是沙尘暴PM2.5,其有机提取物对DNA的损伤作用均比水提取物作用更强,表明PM2.5中引起DNA损伤的主要化学物是有机化合物种类。武威与包头两城市工业水平不同,大气污染程度不同,但两地沙尘暴PM2.5及其水提取物和有机提取物对细胞DNA的损伤作用,在两地之间并无明显差异。[结论]正常天气PM2.5和沙尘暴PM2.5及其水提取物和有机提取物均可引起DNA损伤,且正常天气PM2.5的损伤作用更强;然而不同地方沙尘暴PM2.5毒性作用未见差异,推测其所含遗传毒性化学物可能类似。     

Ambient air pollution and low birth weight in Connecticut and Massachusetts

BACKGROUND: Several studies have examined whether air pollution affects birth weight; however results vary and many studies were focused on Southern California or were conducted outside of the United States. OBJECTIVES: We investigated maternal exposure to particulate matter with aerodynamic diameter < 10, < 2.5 microm (PM(10), PM(2.5)), sulfur dioxide, nitrogen dioxide, and carbon monoxide and birth weight for 358,504 births in Massachusetts and Connecticut from 1999 to 2002. METHODS: Analysis included logistic models for low birth weight (< 2,500 g) and linear models with birth weight as a continuous variable. Exposure was assigned as the average county-level concentration over gestation and each trimester based on mother's residence. We adjusted for gestational length, prenatal care, type of delivery, child's sex, birth order, weather, year, and mother's race, education, marital status, age, and tobacco use. RESULTS: An interquartile increase in gestational exposure to NO(2), CO, PM(10), and PM(2.5) lowered birth weight by 8.9 g [95% confidence interval (CI), 7.0-10.8], 16.2 g (95% CI, 12.6-19.7), 8.2 g (95% CI, 5.3-11.1), and 14.7 g (95% CI, 12.3-17.1), respectively. Lower birth weight was associated with exposure in the third trimester for PM(10), the first and third trimesters for CO, the first trimester for NO(2) and SO(2), and the second and third trimesters for PM(2.5). Effect estimates for PM(2.5) were higher for infants of black mothers than those of white mothers. CONCLUSIONS: Results indicate that exposure to air pollution, even at low levels, may increase risk of low birth weight, particularly for some segments of the population.