Underrepresented groups in WaSH – the overlooked role of chemical toxicants in water and health

In May 2019, the Chemical Abstracts Service registered its 150 millionth unique chemical substance (Wang 2019). Around 100,000 chemical compounds are produced in significant volumes annually (Burton et al. 2017). The rates of chemical production and diversification, particularly within low- and middle-income countries (LMICs), have outpaced the other major drivers of global environmental change such as CO₂ emissions, nutrient pollution, habitat destruction, and biodiversity loss (Bernhardt et al. 2017). The biosphere has a finite capacity for chemical assimilation and many compounds persist and accumulate, thereby threatening ecosystems, water sources, and, ultimately, human health. Chemical pollution is often severe and is increasing in LMICs where the production, use, and the disposal of chemical substances is highly unregulated. Driven by low labor costs, lax environmental and public health protections, and lack of regulatory enforcement, the manufacture and use of chemicals have increasingly shifted to LMICs over recent decades (Landrigan & Fuller 2016; Suk & Mishamandani 2016; Weiss et al. 2016) (Figure 1).

Surveying chemical production trends over recent decades, a 2016 report (Weiss et al. 2016) revealed an exponential rate of growth in LMICs, compared with approximately linear growth in high-income countries (HICs) (Figure 1, data from Weiss et al. 2016). This has in turn led to the increased environmental occurrence and negative impacts on human and environmental health in LMICs (Suk & Mishamandani 2016). Compared with HICs, LMICs lack infrastructure to protect public health and the environment, and face greater difficulties in responding with appropriate policy, technology, management, and enforcement measures (Suk & Mishamandani 2016). Consequently, global public health consequences of chemical pollution are now comparable to or greater than those of widespread infectious diseases such as HIV/AIDS, tuberculosis, and malaria (Landrigan & Fuller 2016; Landrigan et al. 2018; Broadfoot 2019). The UN Sustainable Development Goals (UN-SDP 2015) explicitly aim to ‘reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination’ (3.9), ‘improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials’ (6.3), and ‘achieve the environmentally sound management of chemicals and all wastes throughout their life cycle … and significantly reduce their release to air, water and soil in order to minimize their adverse impacts on human health and the environment’ (12.4). However, chemical pollutants have so far been overlooked in the international development agenda, and pollution control currently receives <0.5% of global development spending (Landrigan & Fuller 2016).

Patterns of pollution and pollution-related diseases change as communities advance through stages of development. In addition to traditional hazards such as infectious disease, indoor air pollution, drinking water contaminated by fecal pathogens, poor sanitation, and inadequate nutrition, people in LMICs are at increasingly high risk of non-communicable diseases (NCDs) driven by exposure to proliferating chemical pollutants (Laborde et al. 2015; Landrigan & Fuller 2016; Suk & Mishamandani 2016). In this way, LMIC communities are thus simultaneously exposed to both old and new forms of pollution and suffer a ‘double burden’ of disease (Landrigan & Fuller 2016). NCDs resulting from chronic and acute exposure to environmental chemicals include neurobehavioral disorders, pediatric and adult cancers, birth defects, obesity, diabetes, hypertension, asthma, reproductive disorders, endocrine disruption, neurodevelopmental disorders, cardiovascular disease, chronic kidney disease of unknown etiology, organ damage, and other health problems (CDC 2009; Laborde et al. 2015; Redmon et al. 2016; Suk & Mishamandani 2016). NCDs have emerged as a leading cause of death and disability in LMICs – for example, 55% of new cancer cases are arising in LMICs and could reach 60% by 2020 (Suk & Mishamandani 2016). Major recent global public health studies have underscored that NCDs are significant and growing factors in the overall burden of disease, including reports by The Lancet (Landrigan et al. 2018), the Journal of Clinical Endocrinology and Metabolism (Woodruff 2015), the Council on Foreign Relations (Daniels et al. 2014), and the World Health Organization (WHO) (Prüss-Ustün et al. 2016).

Exposure to many synthetic chemicals can dysregulate immune function in ways that lead not only to increased vulnerability to NCDs such as cancer but also to greater susceptibility to pathogens and reduced effectiveness of vaccinations against infectious diseases (Winans et al. 2011; Erickson 2019). Maternal and early life exposures to chemicals that impair immune function have been demonstrated to critically increase susceptibility to infections and disease later in life (Winans et al. 2011). Low-dose exposures occurring during developmental windows of heightened susceptibility, for example, periods in embryonic, fetal, and early postnatal life, can have far greater effects than high-dose exposure in adults (Suk & Mishamandani 2016). Immunotoxicity has been demonstrated for compounds within several classes of synthetic chemicals, including organohalogen compounds, such as polychlorinated biphenyls (Heilmann et al. 2006; Winans et al. 2011; Hodges & Tomcej 2016), dioxins (Burleson et al. 1996; Winans et al. 2011), and solvents such as trichloroethylene and toluene (Winans et al. 2011); organophosphate flame retardants (Canbaz et al. 2017) and plasticizers such as phthalates and bisphenol-A (Winans et al. 2011); numerous pesticides, including atrazine and chlordane (Winans et al. 2011; Hodges & Tomcej 2016); and per-/poly-fluoroalkyl substances (PFASs) (Granum et al. 2013; Pennings et al. 2016; Grandjean et al. 2017).

Recent research has correlated maternal levels of PFAS perfluorooctanoate and perfluorohexane sulfonate and gastroenteritis in children (Granum et al. 2013). A study in Bangladesh found that arsenic exposure during pregnancy increased the risk of diarrhea during infancy (Rahman et al. 2011). It is therefore possible that exposure to chemical immunotoxins is partly responsible for the failure of WaSH interventions that target only pathogens to achieve reductions in diarrheal disease and knock-on effects such as stunting.

To-date, the WaSH sector has yet to recognize and grapple with the challenge of mitigating threats to health from chemical toxicants in water. For example, the recently published World Health Organization Household Water Treatment Evaluation Scheme did not take into account chemical safety of drinking water (WHO 2019). Likewise, in interpreting the disappointing results of the WaSH Benefits trials in Bangladesh and Kenya (Luby et al. 2018; Null et al. 2018) and the SHINE trial in Zimbabwe (Humphrey et al. 2019) and identifying next steps for the WaSH sector, Pickering et al. (2019) neglected to consider the role of chemical toxicants. It is our intent to demonstrate a critical need for WaSH to move beyond the current limited focus on microbial pathogens toward a holistic approach to water and health in LMICs that takes chemicals into account. The aim of this Short Communication is to summarize the results of a systematic review identifying studies that focused on chemical water quality and treatment in (1) the Journal of Water, Sanitation, and Hygiene for Development (JWASHDEV) and (2) oral and poster presentations given at the annual University of North Carolina Water & Health Conference (WHC). JWASHDEV and WHC are arguably two of the most important touchstones for assessing the breadth and depth of research and intervention activities in the WaSH sector.

Abstracts of all Research Papers, Practical Papers, Short Communications, Review Papers, Discussions, and Editorials published in JWASHDEV, Volumes 1–8, years 2011–2018, were systematically reviewed (n = 481). Abstract and Conference Program booklets from WHC years 2010–2018 were also reviewed. Abstracts from WHC Poster (P) and Oral (O) presentations were available for years 2012–2015 and 2017–2018. During this timeframe, there were approximately 100 P and 100 O presentations per year. Based on these figures, it was estimated that 1,800 combined P and O presentations took place at WHC from 2010 to 2018. Abstracts from presentations in years 2010–2011 and 2016 were not available. For those years, program booklets listing presentation titles were used for this review.

The terms listed in Table 1 were used to search the JWASHDEV website and the WHC program and abstract booklets for studies that included terms for organic and inorganic chemical contaminants. Organic chemicals were grouped into subcategories: pesticides/herbicides (P/Hs); PFASs; disinfection byproducts (DBPs), including the inorganic DBPs chlorate and bromate; legacy hydrocarbons such as solvents and fuel compounds (LHCs); flame retardants and plasticizers (FR/Ps); pharmaceuticals and personal care products (PPCPs); naturally occurring cyanobacterial and algal toxins and taste and odor compounds (NO); and dye compounds, for example from textile manufacture (DY). Inorganic chemical toxins included in this review were geogenic (GEO) arsenic and fluoride, and the heavy metals (HMs) cadmium, chromium, mercury, nickel, lead, and zinc. All JWASHDEV articles and WHC poster and verbal presentation titles or abstracts that contained one or more search terms were compiled into a database in MS Excel. WHC studies were examined for their applicability in LMICs, as some presentations focused exclusively on the USA or other HICs – for example, a 2012 presentation titled, ‘Evaluation of Public Water System Violations in the USA’. WHC presentations with only HIC applicability were excluded from further analysis. All JWASHDEV articles in the database were found to be applicable in LMICs. All studies were further classified as ‘Class A’ and ‘Class B’ with respect to how chemical contaminants were addressed in the study. ‘Class A’ signified that the study addressed one or more chemical contaminants in a substantive manner, for example, by identifying and/or quantifying in water and/or by evaluating a treatment intervention for the removal of one or more chemicals. ‘Class B’ studies made only passing mention of chemicals. For example, a JWASHDEV article (Alfa et al. 2016) mentions ‘pesticides, insecticides, [and other] oestrogens-mimicking [sic] substances’ as being potential water quality problems in South Africa; however, these compounds were not the subject of the study and were not mentioned again in the paper. The database was queried using the AutoFilter function in MS Excel to quantify the number of Class A studies addressing contaminants in each of the different chemical subcategories. The full Excel database is provided in the Supplementary Information.

Results of the systematic review are presented in the right columns of Table 1. The absolute numbers of Class A studies appearing in JWASHDEV and as combined P and O presentations at WHC are shown. Percentages are also given out of the total of 481 JWASHDEV articles published between 2011 and 2018 and out of an estimated 1,800 combined P and O presentations at WHC from 2010 to 2018. Subcategories do not sum to totals because some studies addressed more than one chemical subcategory.

In total, 43 JWASHDEV studies (8.9%) and 70 WHC presentations (3.9%) were identified that addressed one or more chemical contaminants. Thirty-six JWASHDEV studies (7.5%) and 60 WHC presentations (3.3%) were identified that addressed one or more inorganic chemical contaminants. In JWASHDEV, arsenic, fluoride, and HMs each accounted for roughly 2–3% of articles. Arsenic and fluoride each accounted for <2% of WHC presentations, and HMs <0.5% of presentations. Ten JWASHDEV studies (2.1%) and 12 WHC presentations (0.7%) were identified that addressed one or more organic chemical contaminants. In JWASHDEV, five studies (1%) addressed chemicals in the NO subcategory, four studies (0.8%) addressed DBPs, three studies (0.6%) addressed chemicals in the LHC subcategory, two studies (0.4%) addressed chemicals in the P/H category, one study (0.2%) addressed PPCPs, one study addressed DY compounds, and no studies addressed chemicals in the FR/P or PFAS subcategories. The review of WHC revealed six studies (0.3%) in the P/H subcategory, three studies (0.2%) each in the DPB and PPCP compound categories, two studies (0.1%) of compounds in the DY subcategory, one study (0.06%) each in the LHC, FR/P, and NO subcategories, and no studies of PFASs.

The upper panel of Figure 1 shows the number of studies published in JWASHDEV on inorganic and organic chemical contaminants by year. Total studies published per year and the number of studies identified using search terms ‘pathogen’ and ‘coliform’ are shown for comparison. From the journal's inception until the end of 2018, it published an average of 1.3 studies per year addressing organic chemical contaminants (all compound subcategories combined). JWASHDEV published an average of 1.4 studies per year on arsenic, 1.9 studies per year on HMs, and 2.1 studies per year on fluoride. These averages have been consistent over the journal's history (Figure 1). In contrast, JWASHDEV published 116 articles identified using the search term ‘pathogen’, nearly one-quarter of all articles published 2011–2018. Over the past five years, JWASHDEV has published on average 21 out of 71 articles per year (range 9–33 articles, 12–52% of yearly totals) on ‘pathogens’.

The lower panel of Figure 1 shows the number of combined O and P presentations at WHC on inorganic and organic chemical contaminants by year for 2010–2018. Over this time, an average of 1.3 presentations were made per year addressing organic chemical contaminants (all compound subcategories combined). WHC exposited an average of 3.6 presentations per year on arsenic, 3.8 presentations per year on fluoride, and 0.9 presentations per year on HMs. With around 200 combined O and P presentations made at WHC each year, this translates to, on average, fewer than 2% of presentations focused on arsenic or fluoride and fewer than 0.7% of presentations addressing HMs or organic chemical contaminants.

As an initial step in addressing the gap in WaSH sector programming, the interdisciplinary WaSH-Toxics Working Group (WTWG 2016) has been formed. Its mission is to advance research and deployment of innovative, affordable, and sustainable technologies to control chemical toxicants and supply safe water to resource constrained and developing communities around the world. The major objectives of the WaSH-Toxics Working Group are to:

• Raise the problem of hazardous chemical contaminants to prominence in the global WaSH sector.

• Stimulate targeted innovation of affordable treatment technologies, along with evaluation of existing pathogen-reducing drinking water interventions for potential chemical removal.

• Generate feedback from experts regarding technical merit and real-world applicability of proposed solutions in an iterative design process.

• Elicit commitment to support research, field testing, deployment, and scale-up of toxic chemical control technologies from major WaSH agencies.

• Provide a forum for networking and collaboration among an interdisciplinary cohort of scholars and practitioners to drive progressive awareness and innovation on the topic of Toxics-in-WaSH.

It is free to join, and we encourage the participation of environmental toxicology and health experts, environmental engineers and scientists, water treatment specialists, researchers, development agency program officers, and WaSH practitioners working in the academic, government, non-profit, non-governmental, and private sectors. More information can be found at washtoxics.wordpress.ncsu.edu.

This systematic review concludes that chemical toxicants, particularly organic chemicals of emerging concern, constitute severely underrepresented groups in WaSH sector safe water research and implementation. This journal and the UNC Water and Health Conference serve as bellwethers for WaSH researchers and practitioners. However, addressing organic chemical toxins in ∼2% of journal articles and fewer than 1% of conference presentations is disproportionate to the large and growing impact that these substances have on the environment, water quality, and human health at the global scale, including their contributions to the burden of disease in LMICs. For example, approximately 200 million people in more than 70 countries around the world are exposed to elevated levels of arsenic in their water (Antonova & Zakharova 2016). Despite this, arsenic is addressed in only ∼2% of journal articles and conference presentations each year. Exposure to immunotoxins such as arsenic and many synthetic organic chemicals is known to contribute to acute illnesses; NCDs such as cancer, diabetes, and kidney disease; greater susceptibility to pathogen infections; and reduced effectiveness of vaccinations (Winans et al. 2011; Erickson 2019). However, chemicals remain a blindspot in the WaSH sector. A rapid, pioneering effort is therefore required to focus attention on chemical dimensions of global drinking water quality. Innovative approaches are especially called for given the challenges of chemical contaminant treatability in low-resource settings. As an initial step in addressing this challenge, the interdisciplinary WaSH-Toxics Working Group (washtoxics.wordpress.ncsu.edu) has been formed (WTWG 2016).

The Supplementary Material for this paper is available online at http://dx.doi.org/10.2166/washdev.2019.059.

The authors are grateful to Janhavi Kulkarni and Michaela Bate for assistance with compiling and crosschecking the systematic review database.