Relationship between environmental exposure to toluene,xylene and ethylbenzene and the expired breath concentrations for gasoline service workers

This study evaluated the relationship between the breath concentrations of, and personal exposure to, toluene, xylene and ethylbenzene of thirty workers from ten gasoline stations. Personal exposure air samples and workplace samples were collected simultaneously. Each subject provided a sample of exhaled breath after his or her personal exposure air was sampled. Twenty-five personal air, 17 workplace and 30 breath samples were collected in this study. Results indicated that breath concentrations of toluene and xylene were significantly correlated with personal monitoring concentrations. Furthermore, multiple regression analysis showed that exhaled toluene levels were highly influenced by personal toluene concentrations and the amount of personal gasoline sold (r2 = 0.762), while exhaled xylene levels depended on wind speed and personal xylene exposure concentrations (r2 = 0.665). Exhaled ethylbenzene levels were too low to present a relationship between concentrations and personal exposure levels. The exhaled toluene, xylene and ethylbenzene concentrations ranged from 4.3 to 41.8, 0.9 to 13.9, and 0.2 to 6.5 ppb, and the corresponding personal monitoring concentrations ranged from 60.3 to 572.3, 16.4 to 156.6, and 10.7 to 136.6, respectively. The average number of symptoms per person, according to neurotoxic questionnaire 16 (abbreviated as Q16) was 4.1 and six workers showed over six symptoms in Q16. This study suggests that exhaled toluene and xylene levels are suitable for use as biological exposure indices even at the ppb-level of exposure. Gasoline service workers are exposed to high levels of volatile organic compounds (VOCs) and the potential threats to their neurological systems deserve further investigation.     

Validation of diffusive mini-samplers for aldehyde and VOC and its feasibility for measuring the exposure levels of elementary school children

Exposure to various chemicals can cause adverse effects to health, such as asthma and allergies, especially in children. Data on personal exposure levels in children are scarce, thus small lightweight diffusive mini-samplers for aldehydes and volatile organic compounds (VOCs) were designed to measure the exposure level of children to these chemicals. The aim of the study was to validate and examine the applicability of these mini-samplers for measuring daily chemical exposure. The diffusive mini-samplers are 20 mm in length, 11 mm in diameter, and 1.67 g in weight. The devices are cylindrically shaped with polytetrafluoroethylene membrane filters placed at each end. To measure aldehydes and acetone, 20 mg of 2,4-dinitrophenylhydrazine was used as an absorbent. To measure VOCs, a carbon molecular sieve was used. The sampling rate for each chemical was determined by parallel sampling with active samplers in a closed exposure bag. The blank levels of the chemicals and the storage stability of the device were tested. The mini-samplers were compared to commercially available diffusive samplers. To examine the applicability of the samplers, 65 elementary school children carried them for 24 h. The sampling rates for formaldehyde, acetaldehyde, and acetone were 20.9, 22.9, and 19.7 mL min(-1), respectively. The limits of quantification (LOQ) for the 24-hour sampling by high-performance liquid chromatography/ultraviolet (HPLC/UV) analysis were 8.3, 7.6, and 8.8 μg m(-3) for formaldehyde, acetaldehyde, and acetone, respectively. The sampling rates for the 11 VOCs were determined and ranged from 3.3 mL min(-1) for styrene and 2-ethyl-1-hexanol to 11.7 mL min(-1) for benzene. The LOQ for the 24-hour sampling by gas chromatography-mass spectrometry (GC-MS) analysis ranged from 5.9-105.2 μg m(-3), 1.1-24.7 parts per billion. The storage stability after 5 days ranged from 94.8 to 118.2%. Formaldehyde, acetone, benzene, and toluene were detected above the LOQ in more than 90% of the children, and the median concentrations were 21.7, 20.9, 10.1, and 21.5 μg m(-3), respectively. This study shows that the diffusive samplers developed were suitable for children to carry and were capable of measuring the children's daily chemical exposure.     

Pollution characteristics of volatile organic compounds in the atmosphere of Haicang District in Xiamen City, Southeast China

The compositions, spatial distributions, seasonal variations and ozone formation potential (OFP) of volatile organic compounds (VOCs) were investigated in the atmosphere of Haicang District, Xiamen City, Southeast China. Twenty-four types of VOCs were measured in this study, and ethanol, methylene chloride, toluene, ethyl acetate and isopropyl alcohol were the abundant species based on concentration rank. The concentrations of total VOCs (TVOCs) in industrial areas were higher than those in residential and administrative areas and background site. For industrial areas, the TVOCs concentrations in summer were higher than those in winter, which might result from higher emissions from industrial activities because of stronger evaporation in summer. In contrast, non-industrial areas showed higher concentrations in winter due to the unfavorable meteorological conditions. The spatial distribution of BTEX (benzene, toluene, ethylbenzene and xylene) followed the order of industrial areas > residential and administrative areas > background site, and the concentrations in summer were lower than those in winter for most sites. The high ratios (8.9-14.0) of T/B in this study indicated that industrial emissions were the main sources in this district. X/B ratios were used to assess the ages of air parcels and provided evidence of the transport of air parcels among these sites. Total OFP (TOFP) showed the trend of increase with the increase of TVOCs, and toluene was found as the major contributor to TOFP.     

A Multivariate Time Series Approach to Study the Interdependence among O3, NO x , and VOCs in Ambient Urban Atmosphere

A multivariate time series approach vector autoregression (VAR) along with impulse response function and variance decomposition technique has been employed to look into the interrelationship among O₃, NO, NO₂, and volatile organic compounds (VOCs, namely, benzene, ethylbenzene, toluene, and xylene in the present study) using 3 months long continuous time series data of 1 h average concentration of these pollutants at one of the traffic sites in Delhi, India. It is found that the VAR of order 2 (i.e., past two lagged values of 1 h interval) is sufficient to represent the observed time series at the station studied. The impulse response function and variance decomposition analysis indicate that O₃ concentration shows an immediate rise and persists for a longer duration (typically 8–10 h) once the impulse of NO₂, benzene, ethylbenzene, or xylene is given in the ambient environment. However, in case of toluene, the reverse effect has been observed. Since O₃ forms in the troposphere due to photolysis of NO₂, it is not surprising that its impulse triggers O₃ formation in the ambient environment. However, in case of VOCs, this has been attributed to their tendency to show higher inclination toward intermediary reactions leading to the formation of O₃ rather than their (VOCs) reaction with O₃. Among VOCs, only toluene has been observed to show higher inclination toward its reaction with O₃. Apart from this, variance decomposition technique also reveals that the relation of NO with NO₂ is more important than the relation of NO with O₃ creating a conducive atmosphere for O₃ formation in the present scenario. Thus, the multivariate time series approach provides significant insight about the role played by the dominant individual VOCs and NO _x in influencing the O₃ concentration in ambient urban atmosphere whereas a photochemical modeling approach gives an overall view of NO _x and VOCs behavior with respect to O₃ by using the O₃ isopleth technique.     

Background concentrations of individual and total volatile organic compounds in residential indoor air of Schleswig-Holstein, Germany

During a monitoring campaign concentrations of volatile organic compounds (VOCs) were measured in indoor air of 79 dwellings where occupants had not complained about health problems or unpleasant odour. Parameters monitored were the individual concentration of 68 VOCs and the total concentration of all VOCs inside the room. VOCs adsorbed by Tenax TA were then analysed by means of thermal desorption, gas chromatography and mass spectrometry. The analytical procedure and quantification was done according to the recommendation of the ECA-IAQ Working Group 13 which gave a definition of the total volatile organic compound (TVOC) concentration. Using this recommendation TVOC-concentrations ranged between 33 and 1600 microg m(-3) with a median of 289 microg m(-3). Compounds found in every sample and with the highest concentrations were 2-propanol, alpha-pinene and toluene. Save for a few samples, all concentrations measured have been a factor 2 to 10 lower, compared to data from similar studies. Only a few terpenes and aldehydes were found exceeding published reference data or odour threshold concentrations. However, it has been found that sampling and analysing methods do have a considerable impact on the results, making direct comparisons of studies somewhat questionable. 47% of all samples revealed concentrations exceeding the threshold value of 300 microg TVOC m(-3) set by the German Federal Environmental Agency as a target for indoor air quality. Using the TVOC concentration as defined in the ECA-IAQ methodology is instrumental in assessing exposure to VOCs and identifying sources of VOCs. The background concentrations determined in this study can be used to discuss and interpret target values for individual and total volatile organic compounds in indoor air.     

宁波市环境空气中VOCs污染状况及变化趋势分析

基于近7年来的连续监测数据,对宁波市环境空气中挥发性有机物(VOCs)的污染状况及变化趋势进行了初步分析。研究表明:在宁波市环境空气中检测出94种VOCs,其主要成分是饱和烷烃、芳烃、烯烃、卤代烃、卤代芳烃、含氧有机物等,有37种属有毒有害物质,其中苯系物含量最高;宁波市环境空气中苯系物的污染程度与国内外城市基本处于同一水平,近年来的污染状况变化不大,没有明显恶化;空间分布特征显示一类保护区VOCs的排放以天然源为主,二类各功能区VOCs的排放由天然源和局部人为污染源共同形成,三类区以工业污染源排放为主;时间变化趋势显示VOCs在冬季和春季的平均浓度比其他季节高,VOCs的日变化基本呈现2个主浓度峰值特征,跟城市交通流量变化具有很好相关性。     

典型化工园区大气中挥发性有机物污染调查

对常州市某典型化工园区大气中挥发性有机物(VOCs)污染状况进行了调查。结果表明,该化工园区大气中检出挥发性有机物共有58种,组分有芳香烃、饱和烷烃、卤代烃、烯烃、醛酯类化合物及其他类;苯、甲苯、乙苯、二甲苯为主要挥发性有机污染物,质量浓度为1.0~194μg/m~3;均未超出参考标准的限值。背景点位和园区点位大气中主要ρ总(VOCs)在秋冬季最高,敏感点大气VOCs随季节变化也较为明显;园区T1和T2ρ总(VOCs)年均值高于敏感点位,背景点位年均值最低;园区点位除了汽车尾气排放之外,溶剂的挥发和生产工艺中污染物的排放也增加了大气中苯系物的浓度,同时也对敏感点位和对照点位的大气质量产生了一定的影响。     

Analysis of volatile organic compounds (VOCs) in sediments using in situ SPME sampling

A new method of determining the composition of sediment/soil gases and their volatile organic compound (VOC) content is described. VOCs were collected in situ from intertidal sediments in the Menai Strait and surrounding areas. The sampling was performed using a portable sampler comprising a funnel coupled to a SPME fibre. Gases were extracted from the sediments using a small vacuum pump pulling 100 mL min(-1) at atmospheric pressure. Sixty one different compounds were detected in the samples, and their fluxes and concentrations were determined. The compounds were classified into groups: halogenated, sulfur containing compounds, aldehydes, BTEXs (benzene, toluene, ethyl benzene and xylene) and aliphatic hydrocarbons. Results of principal component analysis (PCA) showed that the chemical composition of extracted gas was influenced primarily by sediment type. Muddy anoxic sediments were dominated by halogenated and sulfur containing compounds and sandy sediments had more aldehydes and BTEXs.     

Assessment of dermal exposure to benzene and toluene in shoe manufacturing by activated carbon cloth patches

OBJECTIVES: The aim of this investigation was to use activated carbon cloth (ACC) patches to study the probability and extent of dermal exposure to benzene and toluene in a shoe factory. METHODS: Inhalation and dermal exposure loading were measured simultaneously in 70 subjects on multiple days resulting in 113 observations. Dermal exposure loading was assessed by ACC patches attached to likely exposed skin areas (e.g. the palm of the hand and abdomen). A control patch at the chest and an organic vapor monitor (OVM) were used to adjust the hand and abdomen patches for the contribution from the air through passive absorption of benzene and toluene on the ACC patches. Systemic exposure was assessed by quantification of unmetabolized benzene (UBz) and toluene (UTol) in urine. RESULTS: Mean air concentrations for the study population were 1.5 and 7.5 ppm for benzene and toluene, respectively. Iterative regression analyses between the control patch, OVM and the dermal patches showed that only a small proportion of the ACC patches at the hand had likely benzene (n = 4; mean 133 microg cm(-2) h(-1)) or toluene (n = 5; mean 256 microg cm(-2) h(-1)) contamination. Positive patches were exclusively observed among subjects performing the task of gluing. Significant dermal exposure loading to the abdomen was detected only for toluene (n = 2; mean 235 microg cm(-2) h(-1)). No relation was found between having a positive hand or abdomen ACC patch and UBz or UTol levels. In contrast a strong association was found between air levels of benzene (p = 0.0016) and toluene (p < 0.0001) and their respective urinary levels. CONCLUSIONS: ACC patches are shown to be a useful technique for quantifying the probability of dermal exposure to organic solvents and to provide estimates of the potential contribution of the dermal pathway to systemic exposure. Using ACC patches we show that dermal exposure to benzene and toluene in a shoe manufacturing factory is probably rare, and when it occurred exposures were relatively low and did not significantly contribute to systemic exposure.     

Assessment of indoor airborne contamination in a wastewater treatment plant

The main objective of this work was to quantify and characterize the major indoor air contaminants present in different stages of a municipal WWTP, including microorganisms (bacteria and fungi), carbon dioxide, carbon monoxide, hydrogen sulfide ammonia, formaldehyde, and volatile organic compounds (VOCs). In general, the total bacteria concentration was found to vary from 60 to >52,560 colony-forming units (CFU)/m³, and the total fungi concentration ranged from 369 to 14,068 CFU/m³. Generally, Gram-positive bacteria were observed in higher number than Gram-negative bacteria. CO₂ concentration ranged from 251 to 9,710 ppm, and CO concentration was either not detected or presented a level of 1 ppm. H₂S concentration ranged from 0.1 to 6.0 ppm. NH₃ concentration was <2 ppm in most samples. Formaldehyde was <0.01 ppm at all sampling sites. The total VOC concentration ranged from 36 to 1,724 μg/m³. Among the VOCs, toluene presented the highest concentration. Results point to indoor/outdoor ratios higher than one. In general, the highest levels of airborne contaminants were detected at the primary treatment (SEDIPAC 3D), secondary sedimentation, and sludge dehydration. At most sampling sites, the concentrations of airborne contaminants were below the occupational exposure limits (OELs) for all the campaigns. However, a few contaminants were above OELs in some sampling sites.     

中国沿海三省主要饮用水源有机物监测

采用固相萃取、吹扫捕集和气相色谱-质谱联用仪(GC-MS)对江苏、浙江、山东省的21个主要地表饮用水源、126份水样中的25种VOCs、38种SVOCs进行定量检测。结果有19种VOCs、10种SVOCs至少在一个水源地多次被检出,其中挥发性氯代烃、苯系物、氯代苯类、酚类、硝基苯类、酞酸酯类、农药为中国或美国环境保护局提出的"水中优先控制污染物",最高检出量为27.79μg/L。三省主要地表水受到有机物轻度污染,水体中VOCs、SVOCs含量尚未超过《地表水环境质量标准》(GB 3838-2002)和《生活饮用水卫生标准》(GB 5749-2006)限值,工业废水排放及农田雨水径流是地表水有机物的重要来源。     

Investigation and assessment of volatile organic compounds in water sources in China

456 water samples collected from 152 water sources in 2006 were analyzed for 21 volatile organic compounds (VOCs). Concentrations of 21 VOCs ranged from below method detection limits of the laboratory to 7.65 ??g/L (toluene), but seldom exceeded the concentration limits set in the National Drinking Water Quality Standards (GB5749-2006) or the National Environmental Quality Standards for Surface Water (GB3838-2002) of China. Of the 21 individual VOCs analyzed, 11 VOCs were detected in at least one sample at or above 1.0 ??g/L; 6.6% of the water samples had a detection of at least one VOC at or above 1.0 ??g/L, and 2.6% had a detection of at least two VOCs at or above 1.0 ??g/L. Based on the statistical data of detection frequencies above the method detection limits, 75% of the samples detected at least one VOC, and 65% of the samples detected at least two VOCs. Chloroform, toluene, and 1,2-dichloroethene were the three most frequently detected VOCs, with detection frequencies of 76.97%, 68.42%, and 44.08%, respectively. Volatile halogenated hydrocarbons and gasoline components were the two most frequently detected VOC groups.     

Lipid peroxidation and antioxidant defense enzymes in Clarias gariepinus as useful biomarkers for monitoring exposure to polycyclic aromatic hydrocarbons

The toxicological evaluations of crude oil, xylene, toluene and benzene were carried out against juvenile stages of Clarias gariepinus. On the basis of LC(50) value, benzene (0.017 ml/l) was found to be the most toxic followed by xylene (0.086 ml/l), toluene (0.398 ml/l) and crude oil (2.219 ml/l) was the least toxic. The results of the lipid peroxidation assay showed that the level of malonaldehyde (MDA) in liver and gills of fish exposed to all the test chemicals increased significantly (P < 0.05) when compared to control. Measurement of activities of antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) in liver and gill of fishes exposed to sublethal concentration of the test chemicals over a 28-day period was found to decrease significantly (P < 0.05) when compared to control. The observed reduction in the activities of antioxidant defense enzymes such as SOD, CAT and GST in conjunction with an increase in MDA levels in the gill and liver tissues of test animals exposed to aromatic hydrocarbon compounds were recommended as a good battery of biomarkers for early detection of pollution during biomonitoring programmes.     

盐城市城区VOCs污染特征及来源解析

2020年4—9月通过离线采样研究了盐城市城区大气中的挥发性有机物(VOCs)浓度水平及组成特征、臭氧生成潜势、二次有机气溶胶生成潜势以及毒性效应等多效应评估和来源贡献。结果表明:盐城市城区VOCs平均体积浓度为35.09×10^-9,盐塘湖公园站点浓度最高;盐城市VOCs主要组分为含氧有机物(OVOCs)和烷烃。通过挥发性有机物多效应评估发现,关键物种为乙醛、对二乙苯、丙酮、甲苯和间/对二甲苯等。采样期间对VOCs浓度的主要贡献来源为二次生成、工业排放和交通排放。     

Analysis of volatile organic compounds released during food decaying processes

A number of volatile organic compounds (VOCs) including acetone, methyl ethyl ketone, toluene, ethylbenzene, m,p-xylene, styrene, and o- xylene released during food decaying processes were measured from three types of decaying food samples (Kimchi (KC), fresh fish (FF), and salted fish (SF)). To begin with, all the food samples were contained in a 100-mL throwaway syringe. These samples were then analyzed sequentially for up to a 14-day period. The patterns of VOC release contrasted sharply between two types of fish (FF and SF) and KC samples. A comparison of data in terms of total VOC showed that the mean values for the two fish types were in the similar magnitude with 280 ± 579 (FF) and 504 ± 1,089 ppmC (SF), while that for KC was much lower with 16.4 ± 7.6 ppmC. There were strong variations in VOC emission patterns during the food decaying processes between fishes and KC that are characterized most sensitively by such component as styrene. The overall results of this study indicate that concentration levels of the VOCs differed significantly between the food types and with the extent of decaying levels through time.     

Performance evaluation of a sorbent tube sampling method using short path thermal desorption for volatile organic compounds

Air sampling, using sorbents, thermal desorption and gas chromatography, is a versatile method for identifying and quantifying trace levels of volatile organic compounds (VOCs). Thermal desorption can provide high sensitivity, appropropriate choices of sorbents and method parameters can accommodate a wide range of compounds and high humidity, and automated short-path systems can minimize artifacts, losses and carry-over effects. This study evaluates the performance of a short-path thermal desorption method for 77 VOCs using laboratory and field tests and a dual sorbent system (Tenax GR, Carbosieve SIII). Laboratory tests showed that the method requirements for ambient air sampling were easily achieved for most compounds, e.g., using the average and standard deviation across target compounds, blank emissions were < or = 0.3 ng per sorbent tube for all target compounds except benzene, toluene and phenol; the method detection limit was 0.05 +/- 0.08 ppb, reproducibility was 12 +/- 6%, linearity, as the relative standard deviation of relative response factors, was 16 +/- 9%, desorption efficiency was 99 +/- 28%, samples stored for 1-6 weeks had recoveries of 87 +/- 9%, and high humidity samples had recoveries of 102 +/- 12%. Due to sorbent, column and detector characteristics, performance was somewhat poorer for phenol groups, ketones, and nitrogen containing compounds. The laboratory results were confirmed in an analysis of replicate samples collected in two field studies that sampled ambient air along roadways and indoor air in a large office building. Replicates collected under field conditions demonstrated good agreement except for very low concentrations or large (> 41 volume) samples of high humidity air. Overall, the method provides excellent performance and satisfactory throughput for many applications.     

Diffusive Sampling of VOCs as an Aid to Monitoring Urban Air Quality

Diffusive sampling of Volatile Organic Compounds (VOCs) onto thermal desorption tubes, followed by gas chromatography, is an established technique for area or personal monitoring of typical workplace concentrations and there has been increasing interest in extending the application to environmental levels, particularly for benzene, toluene and xylene (BTX). Diffusive sampling rates for BTX on Chromosorb 106 and Carbograph-1 (a graphitised carbon) were measured over periods of 1-4 weeks in field validation experiments using ambient air and parallel pumped sampling (the reference method) at the HSL site in central Sheffield. The reference method was also used to investigate the possible bias of an open-path spectrophotometer (OPSIS) used by Sheffield City Council. A bias for BTX was suspected from results of a two-week initial exercise in which several diffusive samplers were placed close to the light path. In the full field validation of the diffusive samplers carried out subsequently, the significant bias of BTX concentrations reported by OPSIS were confirmed when compared with concurrent results from the reference method. OPSIS gave benzene and toluene values up to eight times higher than expected from the GC measurements. Xylene discrepancies were smaller, but in one 3-day peak episode, OPSIS demonstrated a negative correlation with GC.     

嘉善夏季典型时段大气VOCs的臭氧生成潜势及来源解析

2016年8—9月对长三角南部区域嘉善的大气中挥发性有机化合物(VOCs)变化特征、臭氧生成潜势、臭氧生成控制敏感性和来源进行了研究。结果表明,观测期间VOCs总平均值为27.3×10-9,表现为烷烃卤代烃含氧有机物芳香烃烯烃炔烃;VOCs浓度变化较大,早晚出现峰值,与风速呈负相关的关系,与温度没有明显相关性。VOCs的臭氧生成潜势表现为芳香烃烯烃烷烃含氧有机物卤代烃炔烃。甲苯等10种物质对臭氧生成潜势的贡献达到63%。夏季典型时段臭氧生成对VOCs较敏感,属于VOCs控制区。观测期间测得对VOCs浓度贡献较大的物种来源于溶剂涂料和工业排放。     

Determination of volatile organic compounds pollution sources in malaysian drinking water using multivariate analysis

A field investigation was conducted at all water treatment plants throughout 11 states and Federal Territory in Peninsular Malaysia. The sampling points in this study include treatment plant operation, service reservoir outlet and auxiliary outlet point at the water pipelines. Analysis was performed by solid phase micro-extraction technique with a 100 μm polydimethylsiloxane fibre using gas chromatography with mass spectrometry detection to analyse 54 volatile organic compounds (VOCs) of different chemical families in drinking water. The concentration of VOCs ranged from undetectable to 230.2 μg/l. Among all of the VOCs species, chloroform has the highest concentration and was detected in all drinking water samples. Average concentrations of total trihalomethanes (THMs) were almost similar among all states which were in the range of 28.4--33.0 μg/l. Apart from THMs, other abundant compounds detected were cis and trans-1,2-dichloroethylene, trichloroethylene, 1,2-dibromoethane, benzene, toluene, ethylbenzene, chlorobenzene, 1,4-dichlorobenzene and 1,2-dichloro - benzene. Principal component analysis (PCA) with the aid of varimax rotation, and parallel factor analysis (PARAFAC) method were used to statistically verify the correlation between VOCs and the source of pollution. The multivariate analysis pointed out that the maintenance of auxiliary pipelines in the distribution systems is vital as it can become significant point source pollution to Malaysian drinking water.     

Mixing ratios of carbonyls and BTEX in ambient air of Kolkata, India and their associated health risk

Mixing ratios of 15 carbonyls and BTEX (benzene, toluene, ethyl benzene, xylenes) were measured for the first time in ambient air of Kolkata, India at three sites from March to June 2006 and their photochemical reactivity was evaluated. Day and nighttime samples were collected on weekly basis. Formaldehyde was the most abundant carbonyl (mean concentration ranging between 14.07 microg m(-3) to 26.12 microg m(-3) over the three sites) followed by acetaldehyde (7.60-18.67 microg m(-3)) and acetone (4.43-10.34 microg m(-3)). Among the high molecular weight aldehydes, nonanal showed the highest concentration. Among the mono-aromatic VOCs, mean concentration of toluene (27.65-103.31 microg m(-3)) was maximum, closely followed by benzene (24.97-79.18 microg m(-3)). Mean formaldehyde to acetaldehyde (1.4) and acetaldehyde to propanal ratios (5.0) were typical of urban air. Based on their photochemical reactivity towards OH. radical, the concentrations of the VOCs were scaled to formaldehyde equivalent, which showed that the high molecular weight carbonyls and xylenes contribute significantly to the total OH-reactive mass of the VOCs. Due to the toxic effect of the VOCs studied, an assessment for both cancer risk and non-cancer hazard due to exposure to the population were calculated. Integrated life time cancer risk (ILTCR) due to four carcinogens (benzene, ethyl benzene, formaldehyde and acetaldehyde) and non-cancer hazard index for the VOCs at their prevailing level were estimated to be 1.42E-04 and 5.6 respectively.