Indoor Air Pollution in Cars: An Update on Novel Insights

Air pollution exposure in active versus passive travel modes across five continents: A Bayesian random-effects meta-analysis

Epidemiological studies on health effects of air pollution usually estimate exposure at the residential address. However, ignoring daily mobility patterns may lead to biased exposure estimates, as documented in previous exposure studies. To improve the reliable integration of exposure related to mobility patterns into epidemiological studies, we conducted a systematic review of studies across all continents that measured air pollution concentrations in various modes of transport using portable sensors. To compare personal exposure across different transport modes, specifically active versus motorized modes, we estimated pairwise exposure ratios using a Bayesian random-effects meta-analysis. Overall, we included measurements of six air pollutants (black carbon (BC), carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter (PM10, PM2.5) and ultrafine particles (UFP)) for seven modes of transport (i.e., walking, cycling, bus, car, motorcycle, overground, underground) from 52 published studies. Compared to active modes, users of motorized modes were consistently the most exposed to gaseous pollutants (CO and NO2). Cycling and walking were the most exposed to UFP compared to other modes. Active vs passive mode contrasts were mostly inconsistent for other particle metrics. Compared to active modes, bus users were consistently more exposed to PM10 and PM2.5, while car users, on average, were less exposed than pedestrians. Rail modes experienced both some lower exposures (compared to cyclists for PM10 and pedestrians for UFP) and higher exposures (compared to cyclist for PM2.5 and BC). Ratios calculated for motorcycles should be considered carefully due to the small number of studies, mostly conducted in Asia. Computing exposure ratios overcomes the heterogeneity in pollutant levels that may exist between continents and countries. However, formulating ratios on a global scale remains challenging owing to the disparities in available data between countries.

Exposure to airborne particulate matter during commuting using portable sensors: Effects of transport modes in a French metropolis study case

Outdoor exposure to particulate matter (PM2.5 and PM10) in urban areas can vary considerably depending on the mode of transport. This study aims to quantify this difference in exposure during daily travel, by carrying out a micro-sensor measurement campaign. The pollutant exposure was assessed simultaneously over predefined routes in order to allow comparison between different transport modes having the same starting and ending points. During the six-week measurement campaign, the average reference values for PM background concentrations were 13.72 and 17.92μg/m3 for the PM2.5 and PM10, respectively. The results revealed that the mode with the highest exposure to PM2.5 adjusted to background concentration (PM2.5Norm) was the bus (1.65) followed by metro (1.51), walking (1.33), tramway (1.31), car (1.09) and finally the bike (1.06). For PM10Norm, the tramway had the highest exposure (1.86), followed by walking (1.68), metro (1.65), bus (1.61), bike (1.43) and finally the car (1.39). The level of urbanization around the route and the presence of preferential lanes for public transportation influenced the concentration to which commuters were exposed. For the active modes (bike and walking), we observed frequent variations in concentrations during the trip, characterized by punctual peaks in concentration, depending on the local characteristics of road traffic and urban morphology. Fluctuations in particulate matter inside public transport vehicles were partly explained by the opening and closing of doors during stops, as well as the passenger flows, influencing the re-suspension of particles. The car was one of the least exposed modes overall, with the lowest concentration variability, although these concentrations can vary greatly depending on the ventilation parameters used. These results encourage measures to move the most exposed users away from road traffic, by developing a network of lanes entirely dedicated to cycling and walking, particularly in densely populated areas, as well as encouraging the renewal of motorized vehicles to use less polluting fuels with efficient ventilation systems.

Dust dynamics: distribution patterns of semi-volatile organic chemicals across particle sizes in varied indoor microenvironments

An extensive analysis of the distribution patterns of three distinct classes of semi-volatile organic chemicals (SVOCs)-phthalates (PAEs), organophosphate flame retardants (OPFRs), and polycyclic aromatic hydrocarbons (PAHs)-across four distinct size fractions of dust (25, 50, 100, and 200 μm) was conducted. The dust samples were sourced from AC filter, covered car parking lots, households, hotels, mosques, and car floors. To generate the four fractions, ten dust samples from each microenvironment were pooled and sieved utilizing sieving apparatus with the appropriate mesh size. Selected SVOCs were quantified utilizing gas chromatography-mass spectrometry in electron impact (EI) mode. Results unveiled diverse contamination levels among dust fractions, showcasing car parking lot dust with the lowest chemical contamination, while car floor dust displayed the highest levels of PAHs and OPFRs, peaking at 28.3 µg/g and 43.2 µg/g, respectively. In contrast, mosque and household floor dust exhibited the highest concentrations of phthalates, with values of 985 µg/g and 846 µg/g, respectively. Across the analyzed microenvironments, we observed a trend where concentrations of SVOCs tended to rise as dust particles decreased in size, forming a visually striking pattern. This phenomenon was particularly pronounced in dust samples collected from car floors and parking lots. Among SVOCs, PAEs emerged as the predominant contributors with > 90% followed by OPFRs and PAHs. The high levels of OPFRs in car floor dust align logically with the fact that numerous interior components of cars are treated with OPFRs, within a compact indoor microenvironment, to comply to fire safety regulations. Furthermore, petroleum products are a major source of PAHs in the environment and all the sampled cars in the study had combustion engines. Consequently, car dust is more likely to be polluted with PAHs stemming from petroleum combustion. Although previous investigations have noted an increase in heavy metals and brominated flame retardants with decreasing dust particles, this is the first study analyzing these SVOCs in different fractions of dust from various microenvironments. However, aside from two specific microenvironments, the observed pattern of escalating SVOC concentrations with smaller dust particle sizes was not corroborated among the examined microenvironments. This divergence in concentration trends suggests the potential involvement of supplementary variables in influencing SVOC distributions within dust particles.

Concentrations of volatile organic compounds in vehicular cabin air - Implications to commuter exposure

In this study, 117 volatile organic compounds (VOCs) were identified and quantified inside passenger cars and buses operating city and intercity routes. The paper presents data for 90 compounds with frequency of detection equal or greater than 50% that belong to various chemical classes. Total VOC concentration (TVOCs) was dominated by alkanes followed by organic acids, alkenes, aromatic hydrocarbons, ketones, aldehydes, sulfides, amines, and phenols, mercaptans, thiophenes. VOCs concentrations were compared between different vehicle types (passenger cars - city buses - intercity buses), fuel type (gasoline - diesel - liquefied petroleum gas (LPG)), and ventilation type (air condition - air recirculation). TVOCs, alkanes, organic acids and sulfides followed the order: diesel cars > LPG cars > gasoline cars. On the contrary, for mercaptans, aromatics, aldehydes, ketones, and phenols the order was: LPG cars > diesel cars > gasoline cars. Excepting ketones that were found to be higher in LPG cars with air recirculation mode, most compounds were higher with exterior air ventilation in both, gasoline cars and diesel buses. Odor pollution, expressed by the odor activity value (OAV) of VOCs, was highest in LPG cars and minimum in gasoline cars. In all vehicle types, mercaptans and aldehydes were the major contributors to odor pollution of the cabin air with lower contributions from organic acids. The total Hazard Quotient (THQ) was less than 1 for bus and car drivers and passengers indicating that adverse health effects are not likely to occur. Cancer risk from the three VOCs following the order naphthalene > benzene > ethylbenzene. For the three VOCs the total carcinogenic risk was within the safe range. The results of this study expand our knowledge of in-vehicle air quality under real commuting conditions and give an insight into the commuters' exposure levels during their normal travel journey.

Cellular mechanisms linking to outdoor and indoor air pollution damage during pregnancy

Pregnancies are a critical window period for environmental influences over the mother and the offspring. There is a growing body of evidence associating indoor and outdoor air pollution exposure to adverse pregnancy outcomes such as preterm birth and hypertensive disorders of pregnancy. Particulate matter (PM) could trigger oxi-inflammation and could also reach the placenta leading to placental damage with fetal consequences. The combination of strategies such as risk assessment, advise about risks of environmental exposures to pregnant women, together with nutritional strategies and digital solutions to monitor air quality can be effective in mitigating the effects of air pollution during pregnancy.

Working memory-related alterations in neural oscillations reveal the influence of in-vehicle toluene on cognition at low concentration

Although toluene is a typical in-vehicle pollutant, the impacts of in-vehicle toluene exposure on cognitive functions remain unestablished. Therefore, this study aimed to investigate the effects of short-term toluene exposure in vehicles on working memory based on neural oscillations. In total, 24 healthy adults were recruited. Each subject was exposed to four different concentrations of toluene and divided into 0 ppb, 17.5 ppb, 35 ppb, and 70 ppb groups for self-control studies. After 4 h of exposure to each concentration of toluene, a behavioral test of visual working memory was performed while 19-channel electroencephalogram (EEG) signals were collected. Meanwhile, the power spectral density (PSD) and spatial distribution of working memory encoding, maintenance, and extraction periods were calculated by short-time Fourier transform to clarify the characteristic frequency bands, major brain regions, and characteristic channels of each period. To compare the changes in the characteristic patterns of neural oscillations under the effect of different concentrations of toluene. There was no significant difference in working memory reaction time and correct rate between the groups at different toluene concentrations (p > 0.05). The characteristic frequency band of the working memory neural oscillations in each group was the theta frequency band; the PSD of the theta frequency band was predominantly concentrated in the frontal area, and the characteristic channel was the Fz channel. The whole brain (F = 3.817, p < 0.05; F = 4.758, p < 0.01; F = 3.694, p < 0.05), the frontal area (F = 2.505, p < 0.05; F = 2.839, p < 0.05; F = 6.068, p < 0.05), the Fz channel (F = 3.522, p < 0.05; F = 3.745, p < 0.05; F = 6.526, p < 0.05), and the PSD of working memory in the theta frequency band was significantly increased in the 70 ppb group compared with the other three groups during the coding, maintenance, and retrieval phases of working memory. When the in-vehicle toluene exposure concentration was 70 ppb, the PSD of the characteristic frequency bands of working memory was significantly increased in the whole brain, major brain regions, and characteristic channels.

Occurrence of persistent organic pollutants (POPs) in the atmosphere of South Korea: A review

Numerous studies found the presence of persistent organic pollutants (POPs) in various environmental compartments, including air, water, and soil. POPs have been discovered in various industrial and agricultural products with severe environmental and human health consequences. According to the data, South Korea is a hotspot for POP pollution in the southern part of Asia; hence, South Korea has implemented the Stockholm Convention's National Implementation Plan (NIP) to address this worldwide issue. The purpose of this review is to assess the distribution pattern of POPs pollution in South Korea's atmosphere. According to findings, PAHs, PCBs, BFRs, and PBDEs significantly polluted the atmosphere of South Korea; however, assessing their exposure nationwide is difficult due to a shortage of data. The POPs temporal trend and meta-analysis disclosed no proof of a decrease in PAHs and BFRs residues in the atmosphere. However, POP pollution in South Korea tends to decrease compared to contamination levels in neighboring countries like Japan and China.

Indoor Air Quality in Tujia Dwellings in Hunan, China: Field Tests, Numerical Simulations, and Mitigation Strategies

Air pollution is a major health hazard. The traditional habits and unique ethnic fire culture in Hunan Tujia region result in the long-term exposure of residents, especially elderly people, to pollutants. In this study, we conducted field monitoring and assessment of indoor pollutants in the residential houses of Hunan Tujia families and subsequently visualised and simulated fire pollutants in representative residential houses by using fire-dynamic-simulator software. Pollutant-control strategies, using passive smoke collectors and resizing windows, were proposed and simulated for validation. The results revealed that passive smoke collectors reduced the pollutant concentration in the hall house by 43.96%. Furthermore, the optimal window size was 1500 mm × 1500 mm, and the most reasonable windowsill height of the firepit was 1800 mm. The results of the study can be used to improve the indoor air quality of Tujia dwellings and mitigate the adverse health effects of exposure to indoor air pollution without restricting ethnic beliefs and traditional customs.

Partial dust removal in vehicles does not mitigate human exposure to organophosphate esters

Organophosphate esters (OPEs) have been detected within car interior dust, suggesting that the indoor microenvironment of vehicles may represent a potential route of human exposure to OPEs. We recently showed that people with longer commutes are exposed to higher concentrations of tris(1,3-dichloro-2-isopropyl)phosphate (TDCIPP) - a widely used OPE - and other studies have suggested that dust removal may lead to lower exposure to chemicals. Therefore, the overall objective of this study was to determine if a decrease in interior car dust results in mitigation of personal OPE exposure. Participants (N = 49) were asked to wear silicone wristbands, and a subset of them wiped interior parts at the front of their vehicles prior to one study week (N = 25) or both study weeks (N = 11). There were no significant differences in total OPE concentrations (77.79-13,660 ng/g) nor individual OPE concentrations (0.04-4852.81 ng/g) across the different wiping groups nor in relation to participant residence ZIP codes and AC/Heater usage. These findings suggest that higher exposure to TDCIPP for participants with longer commutes may be independent of dust located on interior parts at the front of the vehicle. Therefore, our study demonstrates that there is a need for research on the potential contribution of other sources of TDCIPP exposure within car interiors.

Genetic comprehension of organophosphate flame retardants, an emerging threat to prostate cancer

In recent years, organophosphate ester flame retardants (OPFRs), which have been regarded as alternatives for brominated flame retardants (BFRs), have become widely used in building materials, textiles, and electric equipment. Elucidating the relationship between OPFRs and tumors holds great significance for the treatment and prevention of diseases. In this work, we found a new method for predicting the correlation between the interactive genes of OPFRs and tumors. Transcriptome profiles and OPFR information were obtained from The Cancer Genome Atlas and the Genotype-Tissue Expression, Comparative Toxicogenomics, and PharmMapper databases. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis showed that interactive genes were mainly enriched in prostate cancer, steroid metabolic process, and steroid hormone regulation. Furthermore, protein-protein interaction network analysis revealed 33 biological hub genes. The operating characteristic curves and survival analysis showed the role of key genes in predicting the prognosis of prostate cancer. Gene target prediction and gene set variation analysis proved that OPFRs and their metabolites exert potential effects on prostate cancer. Colony formation assay showed that the cells with AR, mTOR and DDIT3 knockdown could remarkably mitigate the cell proliferation ability in both PC-3 and LNCap cells. Transwell assay demonstrated that the silencing of AR, mTOR and DDIT3 could significantly inhibit the cell invasion capacity of prostate cells. Triphenyl phosphate (TPP) significantly increase the cell proliferation ability and promote cell invasion capacity. AR, mTOR and DDIT3 in the PC-3 and LNCap cells were significantly upregulated with 10-6 M TPP treated.

Exhaustive characterization of (semi-)volatile organic contaminants in car dust using comprehensive two-dimensional gas chromatography ‒ Time-of-flight mass spectrometry

This work represents the first reported effort to build an extensive database of the organic volatile and semi-volatile contaminants present in car dust as a result of migration from materials used in auto-manufacturing. Untargeted analysis of car dust samples has been performed using comprehensive two-dimensional gas chromatography combined with time-of-fight mass spectrometry (GC×GC ‒ToF MS) after generic sample preparation. The enhanced separation power and structural confirmation capabilities provided by this technique have been used for the either positive or tentative identification of 245 GC-amenable compounds, a number of them being identified for the first time in this type of matrix. Information concerning 5 compounds remaining unidentified has also been provided. Results have been summarised in a searchable database containing chromatographic, mass spectral and normalised abundances calculated for the detected analytes in the ten investigated car dusts used to discuss the main findings of the study. Results are expected to serve other researcher to take decisions concerning priority analytes for further evaluation in this research field and for car manufacturers who might search for safer materials.

Inhalation of two Prop 65-listed chemicals within vehicles may be associated with increased cancer risk

Chemicals are listed on California's Proposition 65 (Prop 65) for their potential to cause cancer, birth defects or other reproductive harm, and certain chemicals from this list are often detected within interior vehicle dust and air. Therefore, this study examined the potential risk associated with five Prop 65-listed chemicals detected within vehicle interiors: benzene, formaldehyde, di (2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and tris(1,3-dichloro-2-propyl)phosphate (TDCIPP). Exposure estimates based on time spent within a vehicle were derived from a meta-analysis of estimated concentrations from the literature. Regulatory levels established by the California Office of Environmental Health Hazard Assessment (OEHHA) were then used to generate percent reference doses (%RfDs) for chemical-specific daily doses as well as determine the probability of risk (exceedance probability) as a function of %RfD for each chemical-specific daily dose. Based on our meta-analysis, benzene and formaldehyde were detected in vehicle interior air whereas DEHP, DBP and TDCIPP were detected in vehicle interior dust. Benzene and formaldehyde were the only two chemicals with an estimated %RfD > 100 across any of the commute times. For commute times of 20 min or longer, the %RfD was > 100 for maximum exposures based on the "maximum allowable daily level" for benzene, and for 95th-percentile exposures based on the "no significant risk level" for benzene and formaldehyde. Furthermore, the probability of exceeding 100% RfD was highest for cancer risks associated with benzene, followed by cancer risks associated with formaldehyde and the risk of reproductive and developmental toxicity associated with benzene. Lastly, within the entire state of California, the percent of commuters with a 10% probability of exceeding cancer risk associated with benzene or formaldehyde exposure was 78% and 63%, respectively. Overall, our study raises concerns about the potential risk associated with inhalation of benzene and formaldehyde for people who spend a significant amount of time in their vehicles, an issue that is especially pertinent to traffic-congested areas where people have longer commutes.

Assessment of personal exposure to particulate air pollution in different microenvironments and traveling by several modes of transportation in Bogotá, Colombia: protocol for a mixed-methods study. (Preprint)

Background

Air pollution in most countries exceeds the levels recommended by the World Health Organization, causing up to one-third of deaths due to noncommunicable diseases. Fine particulate matter (PM_2.5) and black carbon (BC) from mobile sources are the main contaminants.

Objective

The aim of this study is to assess the relationship of exposure to air pollutants (PM_2.5 and BC) in microenvironments according to respiratory health and physical activity in users traveling by different types of transportation in Bogotá, Colombia.

Methods

A mixed methods study based on a convergent parallel design will be performed with workers and students. The sample will include 350 healthy transport users traveling by different urban transportation modes in three main routes in Bogotá. The study is broken down into two components: (1) a descriptive qualitative component focused on assessing the individual perception of air pollution using semistructured interviews; and (2) a cross-sectional study measuring the individual exposure to PM_2.5 and BC using portable instruments (DustTrak and microAeth, respectively), pulmonary function by spirometry, and physical activity with accelerometry. The analysis will include concurrent triangulation and logistic regression.

Results

The findings will be useful for the conception, design, and decision-making process in the sectors of health and mobility from public, academy, and private perspectives. This study includes personal measurements of PM_2.5 and BC during typical trips in the city to assess the exposure to these contaminants in the major roadways in real time. The study further compares the performance of two different lung tests to identify possible short-term respiratory effects. As a limitation, the protocol will include participants from different institutions in the city, which are not necessarily representative of all healthy populations in Bogotá. In this sense, it is not possible to draw causation conclusions. Moreover, a convergent parallel design could be especially problematic concerning integration because such a design often lacks a clear plan for making a connection between the two sets of results, which may not be well connected. Nevertheless, this study adopts a procedure for how to integrate qualitative and quantitative data in the interpretation of the results and a multilevel regression. The time that participants must live in the city will be considered; this will be controlled in the stratified analysis. Another limitation is the wide age range and working status of the participants. Regional pollution levels and episodes (PM_2.5) will be handled as confounding variables. The study is currently in the enrollment phase of the participants. Measurements have been made on 300 participants. Pandemic conditions affected the study schedule; however, the results are likely to be obtained by late 2022.

Conclusions

This study investigates the exposure to air pollutants in microenvironments in Bogotá, Colombia. To our knowledge, this is the first mixed methods study focusing on PM_2.5, BC, and respiratory health effects in a city over 2 meters above sea level. This study will provide an integration of air pollution exposure variables and respiratory health effects in different microenvironments.

International Registered Report Identifier (IRRID)

PRR1-10.2196/25690

The Complexity of Space Utilization and Environmental Pollution Control in the Main Corridor of Makassar City, South Sulawesi, Indonesia

Population mobility, increasing demand for transportation, and the complexity of land use have an impact on environmental quality degradation and air quality pollution. This study aims to analyze (1) the effect of population mobility, increased traffic volume, and land use change on air quality pollution, (2) direct and indirect effects of urban activities, transportation systems, and movement patterns on environmental quality degradation and air pollution index, and (3) air pollution strategy and sustainable urban environmental management. The research method used is a sequential explanation design. Data were obtained through observation, surveys, in-depth interviews, and documentation. The results of the study illustrate that the business center and Daya terminal with a value of 0.18 µgram/m3 is polluted, the power plant and Sermani industrial area with a value of 0.16 µgram/m3 is polluted, the Makassar industrial area with a value of 0.23 is heavily polluted, and the Hasanuddin International Airport area with a value of 0.04 µgram/m3 is not polluted. Population mobility, traffic volume, and land use changes have a significant effect on environmental quality degradation, with a determination coefficient of 94.1%. The direct effect of decreasing environmental quality on the air pollution index is 66.09%. This study recommends transportation management on the main road corridor of Makassar City, which is environmentally friendly with regard to sustainable environmental management.

Modeling In-Vehicle VOCs Distribution from Cabin Interior Surfaces under Solar Radiation

In-vehicle air pollution has become a public health priority worldwide, especially for volatile organic compounds (VOCs) emitted from the vehicle interiors. Although existing literature shows VOCs emission is temperature-dependent, the impact of solar radiation on VOCs distribution in enclosed cabin space is not well understood. Here we made an early effort to investigate the VOCs levels in vehicle microenvironments using numerical modeling. We evaluated the model performance using a number of turbulence and radiation model combinations to predict heat transfer coupled with natural convection, heat conduction and radiation with a laboratory airship. The Shear–Stress Transport (SST) k-ω model, Surface-to-surface (S2S) model and solar load model were employed to investigate the thermal environment of a closed automobile cabin under solar radiation in the summer. A VOCs emission model was employed to simulate the spatial distribution of VOCs. Our finding shows that solar radiation plays a critical role in determining the temperature distribution in the cabin, which can increase by 30 °C for directly exposed cabin surfaces and 10 °C for shaded ones, respectively. Ignoring the thermal radiation reduced the accuracy of temperature and airflow prediction. Due to the strong temperature dependence, the hotter interiors such as the dashboard and rear board released more VOCs per unit time and area. A VOC plume rose from the interior sources as a result of the thermal buoyancy flow. A total of 19 mg of VOCs was released from the interiors within two simulated hours from 10:00 am to noon. The findings, such as modeled spatial distributions of VOCs, provide a key reference to automakers, who are paying increasing attention to cabin environment and the health of drivers and passengers.

Microbial Degradation and Valorization of Plastic Wastes

A growing accumulation of plastic wastes has become a severe environmental and social issue. It is urgent to develop innovative approaches for the disposal of plastic wastes. In recent years, reports on biodegradation of synthetic plastics by microorganisms or enzymes have sprung up, and these offer a possibility to develop biological treatment technology for plastic wastes. In this review, we have comprehensively summarized the microorganisms and enzymes that are able to degrade a variety of generally used synthetic plastics, such as polyethylene (PE), polystyrene (PS), polypropylene (PP), polyvinyl chloride (PVC), polyurethane (PUR), and polyethylene terephthalate (PET). In addition, we have highlighted the microbial metabolic pathways for plastic depolymerization products and the current attempts toward utilization of such products as feedstocks for microbial production of chemicals with high value. Taken together, these findings will contribute to building a conception of bio-upcycling plastic wastes by connecting the biodegradation of plastic wastes to the biosynthesis of valuable chemicals in microorganisms. Last, but not least, we have discussed the challenges toward microbial degradation and valorization of plastic wastes.