Pollution of water in Africa: a review of contaminants and fish as biomonitors and analytical methodologies-the case of Senegal

Phytoremediation potential and ecophysiological features of water hyacinth Eichornia crassipes: a case study from Orontes River, Türkiye

The pollution of freshwater resources has become a critical global issue due to intensive and unregulated agricultural practices, rapid urbanization, and industrial expansion along waterways. Phytoremediation, which involves using aquatic macrophytes to remove contaminants from water, is recognized as an environmentally sustainable and cost-effective remediation strategy. This study investigates the phytoremediation capacity of Eichhornia crassipes in reducing heavy metal contamination in the transboundary Orontes (Asi) River within Türkiye's borders. The Asi River, spanning 571 km from Lebanon through Syria to the Mediterranean Sea in Hatay, Türkiye, is severely affected by heavy metal pollution, primarily due to agricultural activities. The study assessed the bioaccumulation potential of E. crassipes, which grows abundantly in the river, focusing on metal accumulation in its petioles. The concentrations of cadmium, cobalt, chromium, and lead in petioles were quantified at 6.69, 23.50, 29.77, and 65.25 mg kg-1, respectively, while the maximum concentrations of these metals in the aquatic habitat were 76.57, 303.26, 693.58, and 106.19 µg L-1, respectively. The effectiveness of phytoremediation can be further enhanced through genetic modification, microbial stimulation, and chemical or natural amendments. These findings illustrate the significant potential of E. crassipes for heavy metal remediation in natural water bodies, contributing to ecosystem conservation, species sustainability, and biodiversity protection.

Environmental DNA Insights into the Spatial Status of Fish Diversity in the Mainstem of the Jialing River

Preserving healthy river habitats is essential for maintaining fish diversity. Over time, anthropogenic activities have severely damaged river habitats, leading to notable changes in fish diversity patterns. Conducting thorough and reliable investigations into fish diversity is crucial for assessing anthropogenic impacts on diversity. In August 2023, a water ecology survey was conducted across 20 terraced river sections in the mainstem of the Jialing River, resulting in the collection of 60 environmental DNA water samples. The survey identified 99 fish species, representing 74 genera across 7 orders and 20 families, with the Cyprinidae exhibiting the highest number of species. The fish communities are predominantly composed of species inhabiting slow flowing water, demersal fish, omnivores, and fish spawning adhesive eggs. Overall, small-bodied fish dominate the mainstem of the Jialing River, and the species preferring flowing habitats are relatively scarce. In addition, geographic division analyses revealed minimal variations in fish species composition and diversity among the terraced reservoirs and across the upper, middle, and lower reaches. Notably, the fish compositions in the middle and lower reaches were found to be similar, indicating a certain degree of convergence in these sections of the Jialing River. In conclusion, this study unveils the current status and distribution pattern of fish diversity in the Jialing River and highlights the extent of anthropogenic activities' impact on fish diversity.

Exposure to drinking water pollutants and non-syndromic birth defects: a systematic review and meta-analysis synthesis

OBJECTIVES

To evaluate the association between drinking water pollutants and non-syndromic birth defects.

DESIGN

Systematic review and meta-analysis synthesis.

DATA SOURCES

A search of MEDLINE, EMBASE and Google Scholar was performed to review relevant citations reporting on birth defects in pregnancies exposed to water pollutants between January 1962 and April 2023.

ELIGIBILITY CRITERIA

Prospective or retrospective cohort, population studies and case-control studies that provided data on exposure to drinking water pollutants around conception or during pregnancy and non-syndromic birth defects. We included studies published in the English language after the Minamata Bay disaster to reflect on contemporary concerns about the effect of environmental pollution and obstetric outcomes.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently read the retrieved articles for content, data extraction and analysis. The methodological quality of studies was assessed using the Newcastle-Ottawa Scale. Included studies were assessed for comparability when considered for meta-analysis.

RESULTS

32 studies met inclusion criteria including 17 cohorts (6 389 097 participants) and 15 case-control studies (47 914 cases and 685 712 controls). The most common pollutants investigated were trihalomethanes (11 studies), arsenic (5 studies) and nitrates (4 studies). The studies varied in design with different estimates of exposure, different stages of gestation age and different durations of exposure to pollutants. 21 articles reported data on any birth defects in their population or study groups and the others on specific birth defects including congenital heart defects, neural tube defects, orofacial defects and hypospadias. An increased risk or higher incidence of overall birth defects was reported by 9 studies and for specific birth defects by 14 studies. Eight studies compared the risk or incidence of birth defects with exposure to different concentrations of the pollutants. The analysis showed an association between higher levels of trihalomethanes (TTMs) and arsenic increase in major birth defects (lower vs higher exposure (OR 0.76, 95% CI 0.65 to 0.89; p<0.001 and OR 0.56, 95% CI 0.39 to 0.82; p<0.005, respectively).

CONCLUSION

The evidence of an association between exposure to average levels of common drinking water chemical pollutants during pregnancy and an increased risk or incidence of birth defects is uncertain. Available evidence indicates that some common chemical pollutants currently found in drinking water may have a direct teratogenic effect at high maternal exposure, however, wide variation in methodology limits the interpretation of the results. Future prospective studies using standardised protocols comparing maternal levels during all three trimesters of pregnancy and cord blood levels at birth are needed to better understand the placental transfer of water pollutants and accurately evaluate individual fetal exposure to drinking water pollutants.

PROSPERO REGISTRATION NUMBER

CRD42018112524.

Kelp as a biomonitor of persistent organic pollutants in coastal areas of China: Contamination levels and human health risk

Kelp, the brown alga distributed in coastal areas all over the world, is also an important medicine food homology product in China. However, the levels and profiles of persistent organic pollutants (POPs) in kelp have not been thoroughly investigated to date. Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and emerging bromine flame retardants (eBFRs) were evaluated in 41 kelp samples from the main kelp producing areas in China. The concentrations of total PCBs, PBDEs and eBFRs were in the range of 0.321-4.24 ng/g dry weight (dw), 0.255-25.5 ng/g dw and 3.00 × 10-3-47.2 ng/g dw in kelp, respectively. The pollutant pattern was dominated by decabromodiphenyl ethane (DBDPE, 13.0 ± 11.7 ng/g dw) followed in decreasing order by BDE-209 (2.74 ± 4.09 ng/g dw), CB-11 (1.32 ± 1.06 ng/g dw). The tested results showed that kelp could reflect the pollution status of PCBs, PBDEs and eBFRs, indicating the suitability of kelp as a biomonitor of these harmful substances. Finally, the data obtained was used to evaluate human non-cancer and cancer risks of PCBs and PBDEs via kelp consumption for Chinese. Though the calculated risk indices were considered acceptable according to the international standards even in the worst scenarios, the POPs levels in kelp should be monitored continuously as a good environmental indicator.