Atmospheric polycyclic aromatic hydrocarbons (PAHs) at urban settings in Pakistan: Spatial variations, sources and health risks.

For the first time, this study presents gaseous and particulate-bound (PM2.5) polycyclic aromatic hydrocarbons (PAHs) in ambient air samples collected from eight major cities of Pakistan. Diurnal air samples (gaseous and PM2.5) were collected in summer 2014 on polyurethane foam and quartz fiber filters using high volume-active air sampler. The US-EPA enlisted 16 priority PAHs in particulate and gaseous phase were measured on gas chromatograph equipped with mass spectrometer detector. The total PAHs concentrations ranged between 188 pg m-3 (in Gilgit), and 2340 pg m-3 (in Lahore). The decreasing order of PAHs concentrations in various cities was in the following order: Lahore > Rawalpindi > Multan > Faisalabad > Karachgi > Peshawar > Quetta > Gilgit. Phenanthrene showed the highest concentration, accounted 18% of total PAHs followed by fluoranthene (12% of total PAHs). This study showed that the gaseous fractions were predominant in the ambient air. Source apportionment analysis revealed that biomass combustion, vehicular emissions and diesel combustion in power generators were the potential PAHs emissions sources. The lifetime lungs cancer risk (LLCR) was in the range of 8.28 × 10-7 to 2.09 × 10-5 depicting mild cancer risk to the residents on exposure to atmospheric PAHs. Therefore, it is recommended to monitor atmospheric PAHs throughout the year and also adopt environmentally friendly fuels to reduce PAHs pollution and health risks in the country.

Elevated exposure to polycyclic aromatic hydrocarbons (PAHs) may trigger cancers in Pakistan: an environmental, occupational, and genetic perspective.

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic compounds which are emitted through incomplete combustion of organic materials, fossil fuels, consumption of processed meat, smoked food, and from various industrial activities. High molecular mass and mobility make PAHs widespread and lethal for human health. A cellular system in human detoxifies these toxicants through specialized enzymatic machinery called xenobiotic-metabolizing (CYP450) and phase-II (GSTs) enzymes (XMEs). These metabolizing enzymes include cytochromes P450 family (CYP1, CYP2), glutathione s-transferases, and ALDHs. Gene polymorphisms in XMEs encoding genes can compromise their metabolizing capacity to detoxify ingested carcinogens (PAHs etc.) that may lead to prolong and elevated exposure to ingested toxicants and may consequently lead to cancer. Moreover, PAHs can induce cancer through reprograming XMEs' gene functions by altering their epigenetic markers. This review article discusses possible interplay between individual's gene polymorphism in XMEs' genes, their altered epigenetic markers, and exposure to PAHs in cancer susceptibility in Pakistan.

Legacy and emerging flame retardants (FRs) in the urban atmosphere of Pakistan: Diurnal variations, gas-particle partitioning and human health exposure.

Atmospheric concentration of legacy (LFRs) and emerging flame retardants (EFRs) including 8 polybrominated diphenyl ethers (PBDEs), 6 novel brominated flame retardants (NBFRs), 2 dechlorane plus isomers (DP), and 8 chlorinated organophosphate flame retardants (OPFRs) were consecutively measured in eight major cities across Pakistan. A total of 96 samples (48 PM2.5 & 48 PUFs) were analyzed and the concentrations of ∑8PBDEs (gaseous+particulate) ranged between 40.8 and 288 pg/m3 with an average value of 172 pg/m3. ∑6NBFRs ranged between 12.0 and 35.0 pg/m3 with an average value of 22.5 pg/m3 while ∑8OPFRs ranged between 12,900-40,800 pg/m3 with an average of 24,700 pg/m3. Among the studied sites, Faisalabad city exhibited the higher concentrations of FRs among all cities which might be a consequence of textile mills and garment manufacturing industries. While analyzing the diurnal patterns, OPFRs depicted higher concentrations during night-time. The estimated risks of all groups of FRs from inhalation of ambient air were negligible for all the cities, according to USEPA guidelines. Nonetheless, our study is the first to report gaseous and particulate concentrations of FRs in air on a diurnal basis across major cities in Pakistan, offering insights into the atmospheric fate of these substances in urban areas in a sub-tropical region.

Isotopic Interpretation of Particulate Nitrate in the Metropolitan City of Karachi, Pakistan: Insight into the Oceanic Contribution to NOx.

Nitrogen oxide (NOx) abatement has become the focus of air quality management strategies. In this study, we examined NOx sources and the atmospheric conversion of NOx in Karachi, Pakistan, a megacity in South Asia with serious particulate pollution problems. Oceanic contributions to NOx were quantified for the first time based on a novel approach using nitrogen/oxygen isotopic analysis in nitrate (δ15N-NO3-; δ18O-NO3-) and a Bayesian model. Our results showed that δ15N-NO3- in Karachi varied between -10.2‰ and +12.4‰. As indicated by the δ18O-NO3- findings (+66.2 ± 7.8‰), the •OH pathway dominated NOx conversion throughout the nearly two-year observation, but high NO3- events were attributed to the O3 pathway. Coal combustion was the most significant source (32.0 ± 9.8%) of NOx in Karachi, with higher contributions in the autumn and winter; a similar situation occurred for biomass burning + lightning (30.3 ± 6.5%). However, mobile sources (25.2 ± 6.4%) and microbial processes (12.5 ± 7.5%) exhibited opposite seasonal trends. The oceanic contributions to NOx in Karachi were estimated to be 16.8%, of which lightning, shipping emissions, and microbial processes accounted for 20.3%, 46.3%, and 33.4%, respectively, emphasizing the dominance of shipping emissions as an oceanic NOx source.

Direct and indirect impact of sewage sludge compost spreading on Quercus coccifera monoterpene emissions in a Mediterranean shrubland.

Monoterpene emissions of Quercus coccifera L. were repeatedly measured during the two years following the spreading of a sewage sludge compost at rates of 50 Mg ha⁻¹ and 100 Mg ha⁻¹, in a twelve-year-old post-fire Mediterranean shrubland. We also monitored the patterns of change in soil and leaf nutrient content, plant water potential, chlorophyll fluorescence, and plant growth. Compost spreading resulted in weak changes in leaf nutrient content and plant water status, and therefore no significant effect on monoterpene emissions at leaf scale, except during one summer sampling, probably related to advanced leaf maturity with the highest compost rate. However, compost increased plant growth, particularly the leaf biomass. The results suggest that compost spreading in Mediterranean shrublands has no strong short-term effect on Q. coccifera monoterpene emissions at leaf level, but may indirectly increase volatile organic compound fluxes at the stand scale, which may contribute to regional ozone pollution.