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.