Agrochemicals in freshwater systems and their potential as endocrine disrupting chemicals: A South African context

Abstract

South Africa is the largest agrochemical user in sub-Saharan Africa, with over 3 000 registered pesticide products. Although they reduce crop losses, these chemicals reach non-target aquatic environments via leaching, spray drift or run-off. In this review, attention is paid to legacy and current-use pesticides reported in literature for the freshwater environment of South Africa and to the extent these are linked to endocrine disruption. Although banned, residues of many legacy organochlorine pesticides (endosulfan and dichlorodiphenyltrichloroethane (DDT)) are still detected in South African watercourses and wildlife. Several current-use pesticides (triazine herbicides, glyphosate-based herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and chlorpyrifos) have also been reported. Agrochemicals can interfere with normal hormone function of non-target organism leading to various endocrine disrupting (ED) effects: intersex, reduced spermatogenesis, asymmetric urogenital papillae, testicular lesions and infertile eggs. Although studies investigating the occurrence of agrochemicals and/or ED effects in freshwater aquatic environments in South Africa have increased, few studies determined both the levels of agricultural pesticides present and associated ED effects. The majority of studies conducted are either laboratory-based employing in vitro or in vivo bioassays to determine ED effects of agrochemicals or studies that investigate environmental concentrations of pesticides. However, a combined approach of bioassays and chemical screening will provide a more comprehensive overview of agrochemical pollution of water systems in South Africa and the risks associated with long-term chronic exposure.

The potential distributions of African Azolla species and their implications for African wetland ecosystems for the future

“…The most recent occurrence records for Azolla nilotica are from Lake Manzala during the 19th century, Edku Lake around the 1920s, and Burullus Lake in the 1960s, all in Egypt (Birks, 2002). Persistent changes in sea level, siltation of Nile distributaries, uncontrolled chemical fertilizer application (Horak et al, 2021), and human interference in diverting Nile waters for irrigation are some of the root causes of A. nilotica's extinction (Kendie, 1999). The current water quality preferences of Azolla are still unknown, which complicates efforts to understand, manage, and potentially mitigate threats to Azolla populations.…”

Herbicides in Camps Bay (Cape Town, South Africa), supplemented

“…Herbicides in the environment represent a potential hazard to living organisms due to their lipophilic properties, which allow bioaccumulation in biota, and their resistance to degradation (Aparecida et al, 2013;Jurado et al, 2011;Wyss et al, 2006;Ying and Williams, 2000;Yu et al, 2016). The majority of herbicide monitoring studies have focused on freshwater, such as lakes, rivers and reservoirs, with a particular focus on organochlorine compounds (Ccanccapa et al, 2016b(Ccanccapa et al, , 2016aHorak et al, 2021;Masiá et al, 2013;Miller et al, 2019;Palma et al, 2014;Papadakis et al, 2015;Tadeo et al, 2008), with a few exceptions see for example (Riascos-Flores et al, 2020;Yang et al, 2019). A large portion of the herbicide residues reach the ocean through agricultural runoff, atmospheric transportation, and sewage discharge (Campo et al, 2013;Knopp et al, 2016;Münze et al, 2017;Pandit et al, 2006;Stamatis et al, 2010).…”

Environmental factors influencing DDT–DDE spatial distribution in an agricultural drainage system determined by using machine learning techniques

“…This region of southeast Spain had endemic malaria until the 1960s (Bueno & Jiménez, 2008), and the presence of large wetlands, irrigation water reservoirs, and irrigation and drainage canals favored the Anopheles mosquitoes, that were combated with an intensive use of insecticides (especially DDT) in the past. The current presence of hotspots of DDT-DDE in surface waters is frequent in areas where malaria was endemic and extensive history of DDT application has left a permanent mark on the environment (Horak et al, 2021). (2) Soil properties, including soil electrical conductivity and soil sand fraction.…”