Occurrence and environmental risks of contaminants of emerging concern across the River Athi Basin, Kenya, in dry and wet seasons.

Globally, the environmental occurrence of Contaminants of Emerging Concern (CECs) including pharmaceuticals (PhACs), personal care products (PCPs) and modern polar pesticides has raised ecological and human health awareness. However, as the developed world races against time to establish regulatory measures to mitigate their effects, developing nations including Kenya are lagging behind, partly due to unavailability of adequate data. In this work, a multi-residue analysis of 86 CECs was carried out on 198 surface water and 18 effluent samples collected at 24 sites across the River Athi basin area, Kenya, in both dry and rainy seasons. Overall, 57 CECs comprising 31 PhACs (0.4 ng L-1-142 µg L-1), 6 PCPs (0.7-570 ng L-1) and 20 pesticides (0.3 ng L-1-8.3 µg L-1) were detected. The maximum loads varied from 217 g day-1 (PCPs) to 46 kg day-1 (PhACs). Individually, carbamazepine, nevirapine, sulfamethoxazole and DEET were the most ubiquitous CECs, with detection frequencies (DF) higher than 80 %. The highest concentrations were observed at river sites that are heavily impacted by informal settlements, highlighting the critical role of slums in urban rivers pollution. At least 8 CECs including acetamiprid, alachlor, atrazine, diuron, nevirapine and paracetamol show potential risk to algae, Daphnia magna and fish, as exemplified by Risk Quotients (RQ) up to 174. Similarly, potential risk of antibiotic resistant bacteria development is evident (RQ up to 64), being driven by metronidazole, sulfamethoxazole and trimethoprim. Ultimately, further studies on the occurrence and distribution of antibiotic resistant bacteria within the basin and among the communities consuming untreated river water for drinking is merited.

Occurrence and point-of-use treatment of contaminants of emerging concern in groundwater of the Nzoia River basin, Kenya.

Groundwater constitutes a major source of fresh water globally. However, it faces serious quality challenges from both conventional pollutants and contaminants of emerging concern (CECs) such as pharmaceutically active compounds (PhACs), personal care products (PCPs) and pesticides. There exists a significant knowledge gap regarding the occurrence of CECs in groundwater, especially in Africa. This study presents unique data on the concentration of fourteen PhACs, five PCPs and nine pesticides in groundwater wells in Nzoia River basin, Kenya. Generally, PCPs were the most dominant class with concentrations up to 10 µg/L (methylparaben). Anti(retro)virals, being important in the treatment of HIV/AIDS, were more prevalent among the PhACs as compared to the developed world, with concentrations up to 700 ng/L (nevirapine). In contrast, pesticides were measured at lower concentrations, the maximum being 42 ng/L (metolachlor). A basic risk assessment shows that - among the detected CECs - carbamazepine may pose medium human health risk and requires further investigation among infants and children. Point-of-use (POU) technologies are being increasingly promoted especially in the developing nations to provide drinking water solutions at the household level, but very little data is available on their performance towards CECs removal. Therefore, besides measuring CECs in groundwater, we investigated ceramic filters and solar disinfection (SODIS) as possible POU treatment options. Both techniques show potential to treat CECs in groundwater, with removal efficiencies higher than 90% obtained for 41 and 22 compounds in ceramic filters and SODIS, respectively. Moreover, for the more recalcitrant compounds (e.g. sulfadoxin), the performance is improved by up to three orders of magnitude when using TiO2 as a photocatalyst in SODIS.

Occurrence and treatment of contaminants of emerging concern in the African aquatic environment: Literature review and a look ahead.

Awareness about the rising detection and reported (eco)toxicological effects of contaminants of emerging concern (CECs, e.g. pharmaceuticals and personal care products - PPCPs - and modern pesticides) in the aquatic environment is growing. CECs are increasingly reported in the African aquatic environment, although the amount of data available is still limited. In this work, a comprehensive review is presented on the occurrence of CECs in wastewater, sludge, surface water, sediment, groundwater and drinking water of Africa. Further attention is given to the performance of wastewater stabilization ponds (WSPs) and trickling filters (TF) with respect to CECs removal. For the first time, we also look at the state of knowledge on the performance of point-of-use technologies (POUs) regarding the removal of CECs in drinking water. Generally, CECs in Africa occur at the same order of magnitude as in the Western world. However, for particular groups of compounds and at specific locations such as informal settlements, clearly higher concentrations are reported in Africa. Whereas antiretroviral and antimalarial drugs are rarely detected in the Western world, occurrence patterns in Africa reveal concentrations up to >100 µg L-1. Removal efficiencies of WSPs and TFs focus mainly on PPCPs and vary significantly, ranging from no removal (e.g. carbamazepine) to better than 99.9% (e.g. paracetamol). Despite the rising adoption of POUs, limited but promising information is available on their performance regarding CECs treatment in drinking water, particularly for the low-cost devices (e.g. ceramic filters and solar disinfection - SODIS) being adopted in Africa and other developing countries.

Occurrence, fate and removal of pharmaceuticals, personal care products and pesticides in wastewater stabilization ponds and receiving rivers in the Nzoia Basin, Kenya.

Although there is increased global environmental concern about emerging organic micropollutants (EOMPs) such as pharmaceuticals, personal care products (PPCPs) and polar pesticides, limited information is available on their occurrence in Africa. This study presents unique data on concentrations and loads of 31 PPCPs and 10 pesticides in four wastewater stabilization ponds (WSPs) and receiving rivers (flowing through urban centres) in Kenya. The WSPs indicate a high potential to remove pharmaceutically active compounds (PhACs) with removals by up to >4 orders of magnitude (>99.99% removal), mainly occurring at the facultative stage. However, there are large differences in removal among the different classes, and a shift in the relative PhACs occurrence is observed during wastewater treatment. Whereas the influent is dominated by high-consumption PhACs like anti-inflammatory drugs (e.g. paracetamol and ibuprofen, up to 1000 µg L-1), the most recalcitrant PhACs including mainly antibiotics (e.g. sulfadoxin and sulfamethoxazole) and antiretrovirals (e.g. lamivudine and nevirapine) are largely abundant (up to 100 µg L-1) in treated effluent. Overall, concentrations of EOMPs in the Nzoia Basin rivers are the highest in dry season (except pesticides) and in small tributaries. They are of the same order of magnitude as those measured in the western world, but clearly lower than what we recently measured in the Ngong River, Nairobi region. Based on the specific consumption patterns and recalcitrant behavior, high concentrations (>1000 ng L-1) are observed in the rivers for PPCPs like lamivudine, zidovudine, sulfamethoxazole and methylparaben. Concentration levels of pesticides are in general one order of magnitude lower (<250 ng L-1). Our data suggest a continuous input of EOMPs to the rivers from both point (WSPs) and diffuse (urban centres) sources. To better understand and manage the impact of both sources, EOMP removal mechanisms in WSPs and their attenuation in rivers merit further research.

Statistical procedures for the determination of linearity, detection limits and measurement uncertainty: A deeper look into SPE-LC-Orbitrap mass spectrometry of pharmaceuticals in wastewater.

This research addresses some critical challenges regarding the validation of a quantitative multi-residue method for pharmaceuticals in wastewater making use of modern SPE-LC-Orbitrap high-resolution mass spectrometry. Particular attention is given to study in detail response linearity, to realistically estimate detection limits, and to express the measurement precision of the analyte concentration, obtained by external calibration. First, linearity of the Orbitrap response showed to be matrix dependent in a counter intuitive way: stronger deviations from linearity were observed for pure solvent standards than for complex matrices like wastewater. Second, detection limits risk to be overestimated for ubiquitously present compounds for which true blank matrix samples are hard to find, leading to false negative findings. A novel and easy applicable methodology is presented to allow a better estimation of detection limits using the response of the natural isotopes. Third, a statistical methodology to estimate the measurement precision of the analyte concentration using basic validation parameters is developed specifically for the context of multi-residue quantification.

From multi-residue screening to target analysis of pharmaceuticals in water: development of a new approach based on magnetic sector mass spectrometry and application in the Nairobi River basin, Kenya.

This paper presents the development and application of a new multi-residue analytical method providing the first data on the environmental occurrence of human pharmaceuticals in Africa, particularly the Nairobi River basin (Kenya). Based on pharmaceutical consumption data available for the Nairobi region, 43 'priority' pharmaceutically active ingredients (PAIs) were selected for this study. On the basis of magnetic sector high-resolution mass spectrometry, a new methodology involving both full-scan screening and selective target analysis has been developed to investigate the presence of the defined priority PAIs. Subsequent analysis of the corresponding standard compounds provided the full confirmation and indicative concentrations (low ng/L-high µg/L) of 10 human PAIs in the Nairobi River. The detected compounds belong to different classes, i.e. antibiotics, analgesic/anti-inflammatory and anti-epileptic drugs, antimalarials and antiretrovirals. Ibuprofen, paracetamol, sulfamethoxazole and zidovudine showed to be the most concentrated PAIs (about 10-30 µg/L). The concentration of the antiretrovirals (lamivudine, zidovudine and nevirapine) is clearly higher than those reported in the literature, although environmental data on this class of PAIs are still very limited. To the best of our knowledge, this is the first study that provides evidence of detection of lamivudine in surface water. The presented unique data on the occurrence of selected PAIs in the aquatic environment of Africa clearly show that the high prevalence of specific diseases like HIV/AIDS infection in developing countries might result in a different pattern of PAIs in environmental waters compared to the more developed regions.