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The China-Pakistan Economic Corridor (CPEC) between China and Pakistan passes through the environmentally fragile region of the Himalayas−Karakorum−Hindukush (HKH). Surging human influence in the form of transportation and tourism may pose a potential threat to the socio-environmental sustainability especially, the water resources of the region. Therefore, it is important to evaluate the status and hydrogeochemistry of freshwater in mountainous catchments. For this purpose, water samples were collected from the Hunza, Gilgit, and Indus River Basins from 2019 to 2020. The physicochemical and biological characteristics of surface water were investigated using the water quality index (WQI), multivariate statistics, Piper diagram, and Gibbs plots. The results revealed high seasonal variability in the hydrochemistry of water samples in all basins. Heavy metals (HM) i.e., arsenic (As), and lead (Pb) were detected in more than 50% of total water samples, whereas cadmium (Cd) and mercury (Hg) were detected in less than 15% of total water samples. 82% of water samples collected during summer and 48% in winter were contaminated with bacterial contamination (Escherichia coli (E. coli) and total coliform (T. coli)). Piper diagram and Gibbs plot suggested that rock weathering and dissolution of carbonate rocks are the dominating factors controlling the chemistry of glacial streams and river water. The results of this study have important implications for policymakers, regulators, and practitioners involved in water and environmental management across CPEC. [ABSTRACT FROM AUTHOR]

The global increase in electronic waste (e-waste) has led to a rise in informal recycling, emitting hazardous heavy metals (HMs) that threaten human health and ecosystems. This study presents the first comprehensive assessment of HM levels in dry deposition and soils at proximity of forty (40) informal e-waste recycling sites across Pakistan, between September 2020 to December 2021. Findings reveal that Zn (1410), Pb (410) and Mn (231) exhibited the higher mean deposition fluxes (μg/m2.day), derived from air samples, particularly in Karachi. Similarly, soils showed higher mean concentrations (μg/g dw) of Mn (477), Cu (514) and Pb (172) in Faisalabad, Lahore, and Karachi, respectively. HMs concentrations were found higher in winter or autumn and lower in summer. In addition, HM levels were significantly (p = 0.05) higher at recycling sites compared to background sites year-round, highlighting the e-waste recycling operations as the major source of their emissions. The I geo index indicated moderate to extremely contaminated levels of Cu, Pb, Cd, and Ni in Karachi, Lahore and Gujranwala. Ingestion was found as a leading human exposure route, followed by dermal and inhalation exposure, with Pb posing the greatest health risk. The Cumulative Incremental Lifetime Cancer Risk (ILCR) model suggested moderate to low cancer risks for workers. Strategic interventions recommend mitigating health and environmental risks, prioritizing human health and ecosystem integrity in Pakistan's e-waste management. [Display omitted] • Informal e-waste recycling in Pakistan emits Zn, Mn, Pb, harming health/ecosystems. • Heavy metal concentration in air and soil for Karachi were the highest and warrant further attention. • Heavy metals in air exhibited seasonality and peaked in autumn/winter. • High human exposure estimates for Pb highlight the need for improved e-waste management in Pakistan. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Measurement of GEM emissions from urban atmosphere in Pakistan. • Open burning, and physical dismantling are common e-waste recycling practices. • E-waste sites from Karachi, Lahore, and Peshawar were found highly contaminated. • Lower seasonal variations indicating the stable emission sources throughout year. • Workers and public living close to these facilities are exposed to hazards of GEM. Detrimental effects of mercury (Hg) on ecosystems and human health have been well-documented. Whereas emissions of gaseous elemental mercury (GEM) from e-waste recycling have been reported in developed countries, much less is known about the situation in the Global South. Using a total of 132 passive air samplers, seasonally resolved concentrations of GEM in air were measured continuously at 32 informal e-waste recycling facilities and background location in Pakistan for a period of one year between September 2020 and December 2021. Annual average GEM concentrations at the studied locations ranged from 1.8 to 92 ng m−3. Among the studied cities, higher concentrations were measured in Karachi (mean ± s.d: 17 ± 22, range: 4.2–92 ng m−3), Lahore (16 ± 4.2, 8.2–22 ng m−3) and Peshawar (15 ± 17, 4.9–80 ng m−3), while lower levels were measured in Hyderabad (6.9 ± 6.2, 3.1–25 ng m−3), consistent with a higher rate of informal recycling activities in metropolitan areas. Seasonally, higher GEM levels occurred during autumn (15 ± 16: 3.3–92 ng m−3) and summer (13 ± 8.7: 1.8–80 ng m−3) than in winter (12 ± 8.4: 2.5–49 ng m−3) and spring (9.2 ± 7.3: 1.8–80 ng m−3), possibly reflecting enhanced volatilization at higher temperatures and/or varying magnitude of recycling operations in different seasons. Policies and strict regulations related to e-waste management should be developed and implemented urgently in the country. [ABSTRACT FROM AUTHOR]

Absorbing aerosols mainly Black Carbon (BC) have potential effects on the hydrological cycle and climate change over the high-altitude regions particularly in South Asia. The BC measurements are sparse in high altitude locations of the world particularly over the Northern regions of Pakistan. This study investigated the diurnal/monthly variations of BC and its climatic impacts during the period of 2016–2017 over four high altitude locations, i.e., Astore, Gilgit, Sost and Skardu located in the Himalaya-Karakorum-Hindukush (HKH) mountain ranges in Northern Pakistan. The Optical Properties of Aerosols and Clouds (OPAC) model was used for the estimation of aerosol optical properties, e.g., Aerosol Optical Depth (AOD), Asymmetry Parameter (AP) and Single Scattering Albedo (SSA) using the BC number density corresponding to the BC mass concentration. Then the model derived optical properties (AOD, AP and SSA), surface reflectance, ozone and water vapor were used in Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model for the calculation of BC aerosol radiative forcing (ARF) at the Top Of Atmosphere (TOA), Surface (SUR) and within the ATMosphere (ATM). The results revealed that the mean monthly BC concentrations were maximum during November (3.05 ± 0.7 μg/m3) as well as in December (3.05 ± 0.5 μg/m3) at Gilgit and minimum during August (1.1 ± 0.3 μg/m3) at Sost. Correspondingly, the diurnal variation of BC concentrations displayed strong fluctuations, with high concentrations in the late night and early morning during November and December for Astore and Gilgit, respectively. Generally, the BC concentrations were maximum/minimum in the morning/evening during May, June, August and September at all locations. The correlation of BC with different meteorological parameters showed that the BC has positive correlation with temperature and wind speed, while negative with relative humidity and rainfall. The HYSPLIT back trajectory analysis revealed that air masses arrived the study locations from both long distance (Turkmenistan, Tajikistan, Uzbekistan, Iran, Afghanistan, India, and China) and local sources. The monthly mean maximum and minimum BC ARF values at SUR (TOA) were found to be −43.7 ± 3.0 W/m2 (−8.2 ± 0.2 W/m2) and −16.4 ± 1.0 W/m2 (−1.2 ± 0.1 W/m2), respectively, giving an averaged atmospheric forcing of 35.7 ± 2.3 W/m2 and 15.2 ± 1.9 W/m2. • The diurnal/monthly variations of BC were analyzed in the least study region of HKH. • Contrasting variation in BC was observed in daytime and nighttime at all locations. • The micro-meteorological parameters have significant influence on the BC variation. • Higher AOD and lower SSA and AP values were reported in winter months. • The large differences between TOA and SRF forcing produce warming effect within ATM. [ABSTRACT FROM AUTHOR]

For the first time, this study presents gaseous and particulate-bound (PM 2.5) polycyclic aromatic hydrocarbons (PAHs) in ambient air samples collected from eight major cities of Pakistan. Diurnal air samples (gaseous and PM 2.5) 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. [Display omitted] • First exposure assessment of gaseous and particle bound (PM 2.5)-PAHs in eight major cities of Pakistan. • 2–4 rings PAHs are predominant in all cities with 80% contribution of the total PAHs. • PAHs levels were higher in Lahore followed by Rawalpindi and Multan. • Biomass combustion, vehicular emissions and diesel combustion were identified as the major PAHs sources. • Lifetime lungs cancer risk (LLCR) model showed mild level cancer risk after PAHs exposure. [ABSTRACT FROM AUTHOR]

This study investigated the changes in air pollutant's concentration, spatio-temporal distribution and sensitivity of changes in air pollutant's concentration during pre and post COVID-19 outbreak. We employed Google Earth Engine Platform to access remote sensing datasets of air pollutants across Asian continent. Air pollution and cumulative confirmed-COVID cases data of Asian countries (Afghanistan, Bangladesh, China, India, Iran, Iraq, Pakistan, and Saudi Arabia) have been collected and analyzed for 2019 and 2020. The results indicate that aerosol index (AI) and nitrogen dioxide (NO 2 ) is significantly reduced during COVID outbreak i.e. in year 2020. In addition, we found significantly positive (P < 0.05, 95% confidence interval, two-tailed) correlation between changes in AI and NO 2 concentration for net active-COVID case increment in almost each country. For other atmospheric gases i.e. carbon monoxide (CO), formaldehyde (HCHO), ozone (O 3 ), and Sulfur dioxide (SO 2 ), insignificant and/or significant negative correlation is also observed. These results suggest that the atmospheric concentration of AI and NO 2 are good indicators of human activities. Furthermore, the changes in O 3 shows significantly negative correlation for net active-COVID case increment. In conclusion, we observed significant positive environmental impact of COVID-19 restrictions in Asia. This study would help and assist environmentalist and policy makers in restraining air pollution by implementing efficient restrictions on human activities with minimal economic loss., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

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 PM 2.5 & 48 PUFs) were analyzed and the concentrations of ∑ 8 PBDEs (gaseous+particulate) ranged between 40.8 and 288 pg/m 3 with an average value of 172 pg/m 3 . ∑ 6 NBFRs ranged between 12.0 and 35.0 pg/m 3 with an average value of 22.5 pg/m 3 while ∑ 8 OPFRs ranged between 12,900-40,800 pg/m 3 with an average of 24,700 pg/m 3 . 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., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Nitrogen oxide (NO x ) abatement has become the focus of air quality management strategies. In this study, we examined NO x sources and the atmospheric conversion of NO x in Karachi, Pakistan, a megacity in South Asia with serious particulate pollution problems. Oceanic contributions to NO x were quantified for the first time based on a novel approach using nitrogen/oxygen isotopic analysis in nitrate (δ 15 N-NO 3 - ; δ 18 O-NO 3 - ) and a Bayesian model. Our results showed that δ 15 N-NO 3 - in Karachi varied between -10.2‰ and +12.4‰. As indicated by the δ 18 O-NO 3 - findings (+66.2 ± 7.8‰), the •OH pathway dominated NO x conversion throughout the nearly two-year observation, but high NO 3 - events were attributed to the O 3 pathway. Coal combustion was the most significant source (32.0 ± 9.8%) of NO x 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 NO x 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 NO x source.