Introduction

Benzene and toluene are volatile organic compounds (VOCs) that significantly threaten human health and the environment. These compounds, part of the BTEX group (benzene, toluene, ethylbenzene, and xylene), contribute to poor air quality and adverse health outcomes. They play an important role in the formation of ground-level ozone, a secondary pollutant that poses risks to respiratory health, particularly in the summer when high temperatures increase ozone levels (Petrus et al. 2024; Zawacki et al. 2018). Additionally, they contribute to the formation of secondary organic aerosols (Henze et al., 2008), affecting climate (Zhu et al. 2022). Major human factors include vehicular emissions, petroleum refineries gasoline evaporation, fuel combustion, solvent use, and gas system leaks. Tobacco smoke and solid waste breakdown also emit these VOCs (Caselli et al. 2010). Benzene and toluene are hazardous air pollutants as classified by US Clean Air Act of 1990, in terms of its carcinogenicity and mutagenicity. Among them, benzene is considered the most toxic, earning a Group 1 human carcinogen classification by the International Agency for Research on Cancer and a Class A human carcinogen designation by the US Environmental Protection Agency. Long-term exposure to benzene can cause serious health problems, including various types of leukaemia, anaemia, genetic mutations, blood disorders, multiple cancers, reproductive issues, and damage to the kidneys, liver, and central nervous system. Short-term exposure to benzene and toluene can result in eye, nose, and throat irritation, fatigue, respiratory difficulties, lung damage, dizziness, memory loss, and a range of respiratory symptoms. Chronic exposure may also have detrimental effects on maternal health and infant development (Kim et al. 2009; IARC 2002; USEPA 1997, 1998). To compute the harmful impacts researchers often compute, Hazard Quotient (HQ), and Lifetime Cancer Risk (LTCR). HQ is used to gauge non-cancerous health effects from a particular substance by comparing the exposure level to a Reference Dose (RfD), which is the maximum daily amount of a substance that can be taken over a lifetime without significant risk. Expressed as a probability, it reflects the chance of developing cancer over a lifetime due to exposure, considering factors like substance potency, exposure duration, and route. In India, the levels of anthropogenic VOCs in the atmosphere have become a significant concern, particularly in urban areas with heavy traffic and industrial activities. Studies show that the amount of VOCs often exceeds the safe limits, contributing to air pollution and posing health risks to the population (Rizwan et al. 2013). Additionally, studies have shown that post-harvest burning of agricultural residue of paddy fields leads to significant contribution to ambient levels of benzenoids in the Northwest Indo Gangetic Plains of India (Chandra & Sinha 2016). In Delhi NCR, where air pollution is a pressing issue, volatile organic compounds (VOCs) such as benzene and toluene pose significant challenges. The rapid pace of urbanization and industrial expansion has only served to amplify the emission of these deleterious substances, predominantly stemming from vehicular exhaust, industrial processes, and combustion activities (Kermani et al. 2021; Mehta et al. 2020). The impact of BTEX in the context of atmospheric chemistry and public health is significant; yet, within the Indian regulatory guidelines, only benzene is subject to an annual threshold limit as per the National Ambient Air Quality Standards (NAAQS). Apart from benzene, there are no established protocols for the quantification of ambient VOC levels. However, the Central Pollution Control Board (CPCB) is progressing in this field and has set an annual limit of 5 μg/m3 for benzene (CPCB 2009). While, BTEX pollutants are recognized for their health hazards, research into their precise concentrations and impacts in India is insufficient, primarily due to the focus on larger cities (Ramírez et al. 2012). In India, previous studies on air pollution have mostly focused on parts of Delhi (Garg et al. 2018; Singh et al. 2016, Kumar et al. 2014) neglecting the entire NCR region, a key factor in the area's overall pollution. Delhi, a landlocked city surrounded by high-rise buildings of Gurugram, Noida, and other parts of NCR, traps pollutants, leading to severe pollution events. The poor ventilation coefficient during winter exacerbates the city's air quality issues, indicating a high pollution potential (Saha et al. 2019; Iyer and Raj 2013). This research addresses this gap by covering the entire Delhi NCR region, known for its high pollution levels, and aims to improve air quality management strategies like the Graded Response Action Plan, crucial during winter and post-monsoon seasons. The study measures benzene and toluene levels, identifies their sources, examines their roles in ozone formation, and assesses both cancerous and non-cancerous health risks for residents and commuters in the region.

Methodology

Site selection and analysis

The study area consists of entire Delhi and National Capital Region (NCR) of India, spanning from coordinates 28.4020° N, 76.8260° E, which includes 62.52% of urban, and 37.48% of rural sections of Haryana, Uttar Pradesh, and Rajasthan. Regions under Haryana and Uttar Pradesh are fast growing areas of the NCR and are about 275 m above the mean sea level, surround Delhi on three sides. The NCR region is a part of the Indo-Gangetic Plain (IGP), and has an area of 55,083 km2 and a population of 46 million with density of population as 1,105 persons per square kilometre which is too high compared to the national levels (National Capital Region Planning Board 2016). The study analysed data from 56 continuous monitoring stations across the National Capital Region of Delhi. After refining the dataset by excluding zero values, outliers, and duplicates, the analysis focused on 10 stations in Haryana, 7 in Uttar Pradesh, 2 in Rajasthan, and 26 in Delhi. Details of these stations along with demography details of NCR is shown in Fig. 1 and Table 1. The area's dynamic weather patterns, characterized by mild winters (December-February; 5–10 °C), semi-arid climate with hot summers (March–May; 40–48 °C), monsoon season (June–August) with heavy rainfall, and the post-monsoon season (September–November) (Praveen et al. 2020). The winds change direction seasonally, blowing from the southwest in summer and from the northwest in winter (Shukla et al. 2020). These unique weather patterns, combined with strategic geographical features, provide an excellent opportunity to study less-known cancer-causing chemicals in the air and their impacts. The region is a hub for commerce, transportation, industry, and some agriculture, with significant pollution coming from vehicles, factories, services, and construction. On regular workdays, many vehicles commute between the NCR and Delhi, influencing the area's dynamics.

Fig. 1
figure 1

Study area map showing Delhi NCR CPCB continuous air quality monitoring stations

Full size image
Table 1 Continuous Air Quality Monitoring Stations across Delhi NCR
Full size table

This study investigates hourly data for two-years, from January 2022 to January 2024, encompassing continuous data for 24 months (730 days) with 24 readings per day per CAAQMS station, for VOCs (benzene and toluene), as well as NO2, NO, and O3. The data collection has adhered to the guidelines of the Central Pollution Control Board (CPCB) and the U.S. Environmental Protection Agency (EPA). A variety of measurement techniques were utilized, including gas chromatography with a photoionization detector (GC-PID) for VOCs, chemiluminescence for NO2 and NO, and ultraviolet (UV) photometry for O3. Meteorological information was obtained from the CPCB’s database, and the planetary boundary layer height (PBLH) data was acquired from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) with a resolution of 0.5 × 0.625° for the years 2022 and 2023. The objective was to identify variations in the benzene and toluene concentrations during rush hours, defined as 9:00 AM to 11:00 AM, and the low traffic hours, from 2:00 PM to 4:00 PM, to understand the impact of vehicular flow on pollutant levels.

Assessment of health risks

To evaluate the health risk assessments, LTCR and HQ have been computed according to USEPA methodology and Zhang et al. (2015). The LTCR calculation begins with determining the daily exposure (E) in mg/kg/day using the Eq. (1):

$$\text{E}=(\text{C x IRa x DA})/\text{BW}$$
(1)

where,

C = benzene concentration in ambient air (mg/m3),

IRa = respiratory rate (0.83m3 h−1 for adults, 0.87m3h−1 for children; Zhang et al. 2015).

DA = duration of exposure (8 h/day) (Indian working hours; as per Ministry of Labour & Employment, Government of India 2023).

BW = body weight (65 kg for adults, 36 kg for children as per USEPA, 2009).

The calculated value of daily exposure (E) has been employed in the Eq. (2), to estimate.

the LTCR,

$$\text{LTCR}=\text{E x SF}$$
(2)

where, SF = Slope Factor (2.9 × 10–2 mg/kg/day−1), as classified by the EPA Cancer classification and stated in the Risk Assessment Information System.

Similarly, the hazard quotient (HQ) has also been estimated through Eq. (3)

$$\text{HQ}=\text{CY}/\text{RfD}$$
(3)

where,

CY = average daily concentration,

RfD = BTEX inhalation reference dose i.e., 0.003, 5, 1, and 0.1 mg/m3, respectively according to ATSDR 2005.

Potential for ozone formation

The ozone formation potential (OFP) has been computed using Carter’s 1994 methodology which considers the maximum incremental reactivity (MIR) to measure this reactivity. The MIR indicates the amount of ozone (in grams) produced for each gram of VOC that initiates the VOC–NOx reaction. It measures a compound’s contribution to ozone production in the atmosphere (Carter 1990, 1994, 2010; Hoque et al. 2008). The MIR value for toluene is 4.02, and for benzene, it is 0.79. The OFP calculation involves multiplying the VOC concentration by its MIR value (Tiwari et al. 2010).

Results and discussion

Hotspot areas

The analysis of data from 56 monitoring stations across Delhi NCR revealed that 18 locations are hotspots for benzene, a known carcinogen, with levels surpassing the NAAQ standard of 5 µg/m3 annually. The monthly hotspot data is catalogued in Table 2, with consistent hotspots including Anand Vihar, Chandni Chowk, Shadipur, Siri fort, NSIT Dwarka, and Okhla from Delhi; Charkhi Dadri, Gwal Pahadi, Jind, Karnal, Palwal, Panipat, Sector 11 Faridabad, Sector 51 Gurgaon, Vikas Sadan Gurgaon from Haryana; and Loni, Muzaffarnagar, and Sector 125 Noida from Uttar Pradesh. These findings highlight the urgent need for interventions to control benzene pollution and safeguard public health in these areas. Similar to the European Commission's progressive measures, which set a benzene limit of 5 µg/m3 in 2000, reduced it to below 1 µg/m3 in 2006, and successfully achieved undetectable levels of benzene in the air by 2010. Similarly, in the context of NCR, these strategies should prioritize reducing benzene exposure through enhanced monitoring, rigorous regulatory measures, and widespread community awareness initiatives.

Table 2 Monthly hotspot areas of benzene (> 5 µg/m3)
Full size table

Effect of meteorology on levels of benzene

Figure 2 illustrates the seasonal changes in the planetary boundary layer (PBL) and wind patterns that influence benzene levels across various locations in Delhi NCR. Benzene concentrations peak at an average of 15.06 µg/m3 in the Loni area of Ghaziabad, Uttar Pradesh. During the winter (PBL height: 376 m) and post-monsoon (PBL height: 438 m) seasons, the maps show a higher prevalence of orange and red dots, indicating benzene concentrations above 5 and 10 µg/m3. The lower PBL height and colder air during these seasons trap benzene at ground level due to inversion, preventing its dispersion (Hosseinpour et al. 2024). In contrast, the summer and monsoon seasons exhibit fewer or no red dots on the map. The higher PBL and increased wind speeds during these seasons promote dispersion of benzene. This is primarily due to a higher ventilation coefficient in summer and monsoon compared to post-monsoon and winter. However, high benzene concentrations can still occur in summer if emissions are high and wind speeds are low. This is observed in the Loni area, which is heavily industrialized and experiences significant vehicular pollution. Similar high summer benzene levels are noted in Sector 51 in Gurgaon and Sector 125 in Noida, primarily due to vehicular pollution. According to the Delhi Statistical Handbook (2023), there are 12 million registered vehicles in the region, with 3.38 million being private cars. Semi-urban areas such as Panipat, Charkhi Dadri, and Palwal also show high benzene concentrations, attributed to agricultural transport (tractors, trucks), vehicular pollution, and industrial activities, including oil refineries. The absence of strict threshold limit rules for high-polluting industries and the non-application of BSVI vehicle standards in these cities, which are slightly distant from Delhi, contribute to elevated benzene levels in these areas. Additionally, during winter, wind direction predominantly towards the north and northeast contributes to pollution accumulation in these hotspot areas within Delhi NCR. The plot supports the data in Table 2, which shows that the highest pollution hotspots occur primarily during the post-monsoon and winter seasons.

Fig. 2
figure 2

Effect of PBL and wind direction on study area (a). Winters (DJF) (b). Summers (MAM) (c). Monsoon (JJA) (d). Post monsoon (SON)

Full size image

Variations in the levels of benzene and toluene during rush hours (peak office time) and off-peak hours (non-rush) are shown in Fig. 3 (a, b). It can be seen that the average of benzene and toluene in the peak period is between 2.44–7.56 and 2.5–29.15 µg/m3 respectively. The concentration range during off peak hours (non-rush hours) is 1.62–6.98, and 2.31–26.11 µg/m3 respectively. The benzene content in the peak period is 0.08–0.5 times that in the non-rush hours. The ratio of gasoline peak hours (rush) to off peak (non-rush) hours is highest in Muzaffarnagar, UP, an important Indian city for sugar, steel and paper industries. Likewise, the toluene content at the peak time is 0.19–0.08 times that of the off-peak hours. The ratio of toluene peak to off peak hours with the highest activity is at Vikas Sadan, Gurugram, Haryana, indication of high vehicular pollution. The results indicate that toluene concentrations are consistently higher than benzene at various locations. This is primarily due to the broader range of sources for toluene, such as vehicular emissions, industrial activities, and the production of paints, paint thinners, adhesives, and chemical intermediates. In contrast, benzene mainly originates from vehicular emissions (particularly from petrol and diesel engines) and industrial processes like oil refineries and chemical manufacturing. Toluene, with no specific emission limits set by national authorities, exhibits a shorter atmospheric lifetime due to higher reactivity, whereas benzene, less reactive, persists longer in the atmosphere (Cui et al. 2022). This persistence contributes to sustained high pollutant levels during both peak and off-peak hours in urban hotspots, highlighting the need for targeted emission control strategies to mitigate their environmental and health impacts effectively.

Fig. 3
figure 3

Rush and non-rush hours concentrations of benzene and toluene at Hotspot areas

Full size image

Toluene to benzene ratio and factor analysis

This study used toluene/benzene ratios and principal component analysis (PCA) to determine the possible sources of these compounds in the ambient air. The T/B ratio varies among sources due to their unique chemical profiles (Do et al. 2011; Liu et al. 2009; Gros et al. 2007; Hellen et al. 2003). For instance, gasoline emissions are characterized by a higher T/B ratio than those from industrial activities The study focused on the T/B ratio, particularly in areas identified as pollution hotspots, and presented the findings in Fig. 4. A T/B ratio nearing one suggests emissions primarily from vehicular traffic, with higher ratios observed closer to emission sources (Garg et al. 2019; Rad et al. 2014). The T/B ratio ranged from 0.59 to 8.17, with the lowest at Sector 125, Noida, and the highest at Anand Vihar, Delhi. The elevated T/B ratio at Anand Vihar points to significant vehicular emissions, likely from the numerous diesel buses operating out of the interstate bus terminal, with toluene being the predominant Volatile Organic Compound (VOC) emitted by diesel engines (Kim and Choi  2020). The T/B ratios reported in this study align with those from other international studies, indicating similar vehicular pollution sources. For example, T/B ratios of 3.6 in Hanoi, 6.9 in Belgium, and 2.3 in Ethiopia were reported, underscoring the global prevalence of vehicular emissions as a primary source of toluene and benzene (Stewart et al. 2021).

Fig. 4
figure 4

Toluene to benzene ratio at hotspot areas

Full size image

Principal Component Analysis (PCA) was applied to identify the primary sources of air pollution, following the methodology outlined by Cruz et al. (2020). Factor Analysis (FA) was used to organize the data into a correlation matrix, which facilitated a clearer understanding of the contributing factors. Factors were considered statistically significant if they had eigenvalues exceeding 1.00 and factor scores above 0.5. Using XLSTAT software, PCA was performed to determine the factor loadings for the three most polluted sites identified as hotspots.

As shown in Table 3, the results of the PCA indicated that three factors explained 65.72% of the total variance in the data. The first factor alone accounted for 30.45% of this variance and is strongly associated with high levels of toluene, benzene, and NO2 at Vikas Sadan, Gurugram, with loadings greater than 0.72. Notably, even higher loadings for toluene and benzene were observed at Loni Ghaziabad and Sirifort, Delhi, exceeding 0.92. The highest loading value, 0.929, was recorded for benzene and toluene at Loni Ghaziabad. This indicates that both vehicular traffic and industrial activities significantly contribute to air pollution at this site. The presence of small- and large-scale manufacturing industries upwind from the city, combined with import and export activities involving light and heavy transportation, the proximity of the Dadri thermal power plant, and nearby petrol and diesel fueling stations, all result in elevated benzene and toluene concentrations in the area. (Behnami et al. 2023). Conversely, at Sirifort Road, Delhi, and Vikas Sadan, Gurugram, the presence of NO2 along with benzene and toluene implicates that vehicular emissions are a major source of pollution. The study also indicates a correlation between NO2 and ozone levels across different sites. At Vikas Sadan, a high concentration of NO2 correlates with a lower ozone concentration, as evidenced by a factor loading of 0.623. Conversely, at Sirifort and Loni, lower NO2 levels are associated with higher ozone concentrations. This suggests that in these areas, NO2 rapidly transforms into ozone due to its short atmospheric lifespan. Additionally, the presence of high benzene and toluene concentrations contributes to ozone formation through reactions with NO2. The appropriate benzene to toluene ratios at these sites indicate significant ozone pollution in conjunction with benzene and toluene, whereas Vikas Sadan, Gurugram, is primarily affected by NO2 pollution, along with benzene and toluene presence.

Table 3 PCA of pollutants & met parameters at top three hotspot areas
Full size table

Carcinogenic and non-carcinogenic risk assessment

This investigation assessed the potential health risks posed by benzene, aiming to understand the persistent outcomes of being exposed to benzene, which may result in cancer and a range of other negative health impacts on individuals (Mohammadi et al. 2020). The study computed the average daily exposure levels (E) (mg/kg/day) to inhaled benzene in two different groups (adults and children). The assumed exposure duration was 08 h/day for adults and children both (USEPA 1998, 2010, Masih et al. 2016). The LTCR’s acceptable threshold for both adults and children stands at 1 × 10–6, following USEPA guidelines, while the WHO’s threshold is 1 × 10–5. According to Sexton et al. (2007), the cancer risk is divided into three levels. Definitive risk: LTCR exceeds 1.0 × 10–4, Probable risk: LTCR ranges between 1 × 10–5 and 1 × 10–4, and Possible risk: LTCR falls between 1 × 10–6 and 1 × 10–5. The findings revealed that, the maximum average daily exposure levels for adults were 2.41 × 10–3, 2.51 × 10–3, and 2.27 × 10–3 mg/kg per day for 1–8 AM, 8–16 PM, and 16–24 AM respectively at Loni area of Ghaziabad respectively. While children had average daily exposure levels of 1.27 × 10–3, 1.14 × 10–3, and 1.20 × 10–3 mg/kg/day for 1–8 AM, 8–16 PM, and 16–24 AM respectively at Loni area of Ghaziabad respectively. The LTCR values (cancer risk) for both adults & children ranged from 3.30 × 10–5 to 6.98 × 10–5, exceeding the USEPA guidelines limit (1 × 10–6) and the World Health Organization limit (1 × 10–5). The study determined that individuals living in hotspot areas are likely at probable risk of cancer due to benzene exposure. It was observed that the Lifetime Cancer Risk (LTCR) was higher for children than for adults across all hotspot areas and at all times, especially in the morning (1–8 am) and evening to night hours (16–24 pm), as illustrated in Fig. 5. The elevated risk observed in children could be due to their smaller body mass relative to adults, which leads to a higher relative exposure when considering the dose per body weight, as exposure is inversely related to body weight.

Fig. 5
figure 5

Life time cancer risk (LTCR) at hotspot areas during different time intervals for adults (a) and children (b)

Full size image

The Hazard Quotient (HQ), commonly referred as non-cancer risk index, provides an estimate of the likelihood of developing non-cancerous health problems due to air pollutants. HQ values greater than 1 indicate that continuing exposure can lead to cardiovascular, and respiratory illness, while values below 1 are considered acceptable (Baberi et al. 2022; Dehghani et al. 2018; Garg et al. 2018; Zhang et al. 2012). The study found that non-carcinogenic risks such as dizziness, weakness, fatigue, nausea, and irritation of the eyes, skin, and respiratory tract due to benzene exposure remained significantly high (above 1) for the population in all hotspot areas, as shown in Fig. 6. The maximum HQ value i.e., 3.93 for benzene exposure was found at Loni, Ghaziabad, and the minimum was found at NSIT Dwarka, Delhi i.e., 1.37. These results suggest that the long-term benzene concentrations in the study area are associated with an increased danger of developing cardiovascular and respiratory diseases. This research concluded that the individual HQ values for benzene, were above the acceptable limits, indicating a risk of non-cancerous illness from inhalation exposure. The study identifies high LTCR and HQ values of benzene raising concern for the population, particularly children during all the time in a day.

Fig. 6
figure 6

Hazard Quotient (HQ) of benzene & toluene at hotspot areas

Full size image

Ozone production potential of benzene & toluene

The study examines the role of volatile organic compounds (VOCs) in O3 production through photochemical reactions. Ozone Formation Potential (OFP) is a metric used to estimate the capability of VOCs to produce ozone in the urban atmosphere. This research predicted the OFP for various hotspots in the Delhi NCR region, presenting the findings in a Table 4. The Maximum Incremental Reactivity (MIR) coefficients for benzene and toluene are 0.72 and 4.00, respectively, which suggests that toluene is a more significant contributor to ozone formation. However, the Ozone Formation Potential (OFP) is not solely influenced by the Maximum Incremental Reactivity (MIR) coefficient; the actual concentration levels of Volatile Organic Compounds (VOCs) in the ambient air also plays a significant role.

Table 4 Ozone formation Potential of Benzene & Toluene at different areas of Delhi NCR (Hotspots)
Full size table

Elevated concentrations of volatile organic compounds (VOCs) can lead to an increase in secondary aerosol formation (Goel et al. 2024). The average OFP values for benzene and toluene in the hotspot areas are detailed in the Table 4, with the highest toluene concentration at Charkhi Dadri, Haryana (29.65 ± 2.26 µg/m3), followed by Karnal (Haryana) and the highest benzene concentration at Loni Ghaziabad (7.3 ± 0.8 µg/m3) followed by Sector 51, Gurugram. The trend of toluene exceeding benzene was consistent across all hotspots except for Sector 125, Noida. The total OFP levels were particularly high at Charkhi Dadri, surpassing the World Health Organization’s air quality guidelines of 120 μg/m3. The findings indicate that toluene contributes significantly to ozone formation, which is consistent with similar studies conducted in other cities (Shan et al. 2023; Feng et al. 2018). Ozone is recognized as a harmful air pollutant due to its various adverse effects on human health, including respiratory issues and the potential to reduce lung capacity (Holm and Balmes 2022; Pinthong et al. 2022). High OFP levels could result in a range of respiratory symptoms and have been linked to premature deaths in studies around the world (Wu et al. 2022; Kim et al. 2020).

The ozone formation potential (OFP) of NO, NO₂, benzene, and toluene was also analyzed across different time intervals: 0–8 am, 9–16 pm, and 17–23 pm. The data indicate that nighttime chemistry involving NO and benzene contributes to ozone formation as shown in Fig. 7. As sunlight increases in the morning, the formation of ozone is primarily driven by NO, followed by benzene, toluene, and NO₂. NO₂ rapidly photolyzes in sunlight (wavelength ≥ 343 nm) to produce NO and atomic oxygen, which then reacts with O₂ to form ozone (Kaushik and Das 2023; Berezina et al. 2020; Han et al. 2011).

Fig. 7
figure 7

Ozone formation percentage of NO, NO2, benzene and toluene

Full size image

During the evening (6–7 pm), the chemistry shifts, and NO becomes more prominent in forming ozone. VOCs act as catalysts for ozone formation during the morning and afternoon under UV-A radiation. However, in the evening, reduced UV-A radiation leads to higher VOC concentrations and lower ozone levels (Lefohn et al. 2018). In areas with high NO emissions, ozone formation is limited due to NOx titration, where NO breaks down ozone into O and O₂. Thus, ozone levels depend on the transport of NO₂ and VOCs to areas with optimal concentration ratios and sufficient sunlight for ozone production.

Conclusion

This study comprehensively assessed benzene and toluene emissions in Delhi NCR, their health risks, and their contribution to ozone formation. It identified eighteen hotspot areas across Delhi, Haryana, and Uttar Pradesh where benzene levels exceeded the national safe limit of 5 μg/m3. Seasonal and meteorological influences, such as lower planetary boundary layer (PBL) height and wind speeds during winter and post-monsoon seasons, contributed to higher benzene levels due to pollutant trapping, with traffic emissions being a major source, especially during rush hours. Health risk assessments indicated that benzene exposure pose significant risks for residents in these hotspot areas, exceeding recommended limits. The non-cancerous health risk (HQ) for benzene was also above 1, indicating potential respiratory and cardiovascular issues, with children at higher risk due to lower body weight. Toluene was identified as a more significant contributor to ozone formation compared to benzene, owing to its higher Maximum Incremental Reactivity (MIR) value. Elevated VOC concentrations, particularly toluene, led to high Ozone Formation Potential (OFP) levels, exceeding WHO air quality guidelines in some areas and posing a risk for respiratory problems. Overall, the study highlights the concerning levels of benzene and toluene in Delhi NCR and their detrimental impact on public health and air quality. It underscores the need for stricter emission control measures, the promotion of cleaner fuels and technologies, and strategic urban planning to mitigate these issues. Further research is recommended to explore additional mitigation strategies and to assess the effectiveness of existing control measures.