A Quantitative Assessment and Biomagnification of Mercury and Its Associated Health Risks from Fish Consumption in Freshwater Lakes of Azad Kashmir, Pakistan

First insights into per-and polyfluoroalkyl substance contamination in edible fish species of the Indus water system of Pakistan

Per- and polyfluoroalkyl substances (PFASs) are a group of emerging contaminants, that have a wide range of applications in industrial and commercial products. The direct discharge of untreated industrial and domestic wastewater into freshwater bodies is a common practice in developing countries, which are the main contributors to PFASs in the aquatic environment. The situation is further worsened due to poor wastewater treatment facilities and weak enforcement of environmental regulations in countries like Pakistan. The current study was designed to assess PFASs contamination in muscle tissues of edible fish species from major tributaries of the Indus System, including Head Panjnad (HP), Head Trimmu (HT), Chashma Barrage (CB), Head Blloki (HB) and Head Qadirabad (HQ). The analysis of target PFAS was performed using ultrahigh-performance liquid chromatography coupled with a quadrupole Orbitrap high-resolution mass spectrometry. The highest levels of ∑17PFASs were observed in S. seenghala, C. mirigala from HB, and C. mirigala from HQ with a mean value of 45.4 ng g-1, 43.7 ng g-1, and 40.8 ng g-1, respectively. Overall, the compositional profile of fish samples was predominated by long-chain PFASs such as PFOA, PFOS, PFHpS, and PFDS. The accumulation of PFASs in fish species is dependent on the physiochemical properties of PFASs, characteristics of the aquatic environment, and fish species. Significant associations of PFASs with isotopic composition (p < 0.05), feeding habits (p < 0.05), and zones (p < 0.05) indicate that dietary proxies could be an important predictor of PFASs distribution among species. The C7-C10 PFASs exhibited bio-accumulative tendency with an accumulation factor ranging from 0.5 to 3.4. However, none of the fish samples had sufficiently high levels of PFOS to cause human health risk (HR < 1). For future studies, it is s recommended to conduct seasonal monitoring and the bioaccumulation pattern along trophic levels of both legacy and emerging PFASs.

Gaseous elemental mercury emissions from informal E-Waste recycling facilities in Pakistan

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.

Genotoxicity effects in freshwater fish species associated with gold mining activities in tropical aquatic ecosystems

The main aim of this study was to investigate total mercury (THg), methylmercury (MeHg) and arsenic (As) concentrations, and their genotoxic effects on fish species in freshwater habitats impacted by gold mining activities in the Mojana and Bajo Cauca regions (Northern Colombia). A total of 255 individuals of Prochilodus magdalenae (PM) and Hoplias malabaricus (HM) were collected in different areas of northern Colombia, 205 in the exposed groups: Mojana 1 (61), Mojana 2 (81) and Bajo Cauca (63); and 50 individuals in the control group. Dorsal muscle was analysed for pollutants and blood to perform micronucleus (MN) and erythrocytic nuclear alterations (ENA) tests. The results of the MN revealed statistically significant (p < 0.05) genetic damage in both PM (Mojana 1 = 29.7 ± 14.2; Mojana 2 = 25 ± 6.25; Bajo Cauca= 26.6 ± 10.6) and in HM (Mojana 1 = 17.7 ± 7.8; Mojana 2 = 20.4 ± 6.3; Bajo Cauca= 20.8 ± 9.8) compared to the control group (PM= 10.5 ± 3.6; HM= 9.1 ± 3.9). Likewise, the frequency of ENA was statistically higher in the exposed groups compared to the control group (p < 0.05). On the other hand, the concentrations of THg, MeHg and As found in tissue samples were significantly higher (p < 0.05) compared to the control group, being the Bajo Cauca region the area of highest risk due to high concentrations of THg (651.2 ± 344.5 μg/kg for HM and 678.5 ± 983.9 μg/kg for PM) and MeHg (504.6 ± 220.9 μg/kg for HM and 606.8 ± 886.4 μg/kg for PM). Results showed that mean THg values for both species in Bajo Cauca exceeded the WHO maximum limit (set in 500 μg Hg/kg) in fish for human consumption. Results suggest that DNA damage in erythrocytes is associated with the presence of Hg, MeHg and As, coming from mining activities.