Quantifying the impact of climate change on enteric waterborne pathogen concentrations in surface water
Highlights
► Climate change impacts on waterborne pathogen concentrations in surface water. ► These concentrations are expected to increase. ► Available ecological and hydrological scenario studies provide opportunities. ► Statistical and process-based models and climate scenarios help quantify the impacts.
Introduction
Diarrhoea caused by waterborne pathogens is a problem worldwide [1, 2]. In developed countries outbreaks are reported regularly [e.g. 3], but in developing countries the problems are larger due to poor sanitation and drinking water facilities. In low-income countries, diarrhoea is the 3rd leading cause of death [4]. Climate change — in addition to other factors, such as land-use change [5, 6, 7] (which are important, but not the focus of this review) — increases the risk of disease caused by waterborne pathogens [e.g. 8, 9, 10, 11, 12, 13]. Qualitatively, the impacts of climate change on disease caused by waterborne pathogens seem well established. For instance, many disease outbreaks have been connected to floods [e.g. 14] and the number of floods is expected to increase with climate change [15]. However, quantitative proof of these impacts is still problematic and many papers have called for further research on this topic [e.g. 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23•, 24, 25, 26, 27, 28] McMichael et al. [29] estimate that in 2000, 3% of the diarrhoea cases worldwide were caused by climate change but this number is very uncertain due to data limitations [30]. Their values are, however, consistent with a study by Kolstad and Johansson [31•], who also acknowledge the apparent uncertainties. Other recent studies show a statistical relationship between diarrhoea and climate variables [e.g. 1, 14, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50], but many problems remain. A major problem is the availability of complete epidemiological data [2]. In developing countries surveillance and reporting systems may not have been in place for a long time, and patients with diarrhoea will not necessarily attend a doctor so their illness may go unreported. Moreover, there are many other complicating factors in epidemiological research. For example, confounding variables, such as additional transmission routes (for instance person-to-person contact) may confuse results. Another evident example is that seasonality of water source and latrine usage is often not accounted for in a comparison with seasonality of water quality. This may result in incorrect conclusions [51, 52].
Risk of disease is dependent on the pathogen concentration in water [53, 54]. The concentration of pathogens in the water is also expected to be impacted by climate change [55], similar to the risk of disease. Observations of waterborne pathogens may be problematic (e.g. difficulty with recovery rates of protozoa or incomplete cover of observations) [e.g. 56, 57], but for several pathogens and regions thorough observations are available. This review therefore focuses on pathogen concentrations in surface waters.
Quantification of the impact of climate change on the concentration of pathogens in surface water is also still in its infancy. To the author's knowledge, so far only one study quantitatively showed that a future increase in water temperatures will likely increase the inactivation rate of pathogens [58]. This indicates that the waterborne pathogen concentrations could decline with climate change. However, the consequences of changes in precipitation are ignored. There are many opportunities to quantitatively study the impacts of climate change on waterborne pathogen concentrations. The objective of this paper is to show these opportunities by reviewing the recent literature. The review first briefly discusses the impacts of climate change on concentrations of waterborne pathogens qualitatively. Then it assesses and discusses opportunities for quantitative approaches, focussing on statistical and process-based models and using experiences from other fields.
Section snippets
Conceptual model
Figure 1 conceptually describes the fate of waterborne pathogens in the environment and the impacts of climate change on concentrations of waterborne pathogens in the surface water. This figure summarises the different pathways that are described in the literature. The conceptual model shows two main pathways to the environment: point sources from humans through waste water treatment plants (that may have differing efficiencies in removing pathogens), and diffuse sources from humans and animal
Statistical modelling
Many studies have shown a relationship between precipitation, runoff or discharge and the concentration of faecal indicator organisms or waterborne pathogens in surface water [e.g. 51, 64, 73, 74, 75, 76, 77, 78, 79, 80, 81] and several have proven this relationship to be statistically significant [e.g. 54, 82, 83, 84, 85, 86, 87, 88, 89, 90]. Most of these studies focus on precipitation but some have also considered water temperature. Positive correlations have been observed between water
Process-based modelling
Another way to estimate waterborne pathogen concentrations is process-based modelling. Several waterborne pathogen models simulate this at catchment [101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111] and country [112] level. The models generally include the processes shown in black in Figure 1. The available models still have many limitations. Oliver et al. [113•], Pachepsky et al. [114] and Jamieson et al. [115] review the models and their limitations, which include, for example, lack of
General discussion points
The models that are suitable for use in climate impact studies exist only for catchments in developed countries (mainly Australia, United States and Europe). This is problematic. As described in the introduction, the problems with diarrheal disease are largest in developing countries [7]. However, these areas are data sparse and no modelling experiments have been done there. Modelling waterborne pathogens in the developing countries and the impact of climate change on these pathogens there is a
Conclusion
This paper has given a review of the literature for opportunities to quantify the impact of future climate change on pathogen concentrations in surface waters. This topic is important, because every year still nearly two million children die due to diarrhoeal diseases [145, 146] and many more children and adults are affected. This number could well increase due to climate change. Examples from ecological and hydrological modelling of shifting species and changed water flows show that
References and recommended reading
Papers of particular interest, published within the period of review, have been highlighted as:
• of special interest
References (146)
- et al.
Seasonality of cryptosporidiosis: a meta-analysis approach
Environ Res
(2009) - et al.
Climate change and human health: impacts, vulnerability, and mitigation
Lancet
(2006) - et al.
Impact of climate change on health: what is required of climate modellers?
Trans R Soc Trop Med Hyg
(2007) - et al.
Climate change and human health: present and future risks
Lancet
(2006) - et al.
Climate change: a time of need and opportunity for the health sector
Lancet
(2009) Global climate change and infectious diseases
N Engl J Med
(2010)- et al.
Vulnerability of waterborne diseases to climate change in canada: a review
J Toxicol Environ Health, Part A
(2009) - et al.
Effects of EI Niño and ambient temperature on hospital admissions for diarrhoeal diseases in Peruvian children
Lancet
(2000) - et al.
The epidemiology of acute diarrhoea in a rural community in Imo State, Nigeria
Trans R Soc Trop Med Hyg
(1987) - et al.
Cyclospora cayetanensis infections in Haiti: a common occurrence in the absence of watery diarrhea
Am J Trop Med Hyg
(1999)
Seasonal peaks in Escherichia coli infections: possible explanations and implications
Clin Microbiol Infect
Impacts of climate change on surface water quality in relation to drinking water production
Environ Int
Cryptosporidium and Giardia in swimming pools in the Netherlands
J Water Health
Climate change impacts and adaptation: a science agenda for the Environment Agency of England and Wales
Weather
Fate and transport modeling of potential pathogens: the contribution from sediments
J Am Water Resour Assoc
Climate change and effects on water quality: a first impression
Water Sci Technol
Microbiological surveillance of private water supplies in England — the impact of environmental and climate factors on water quality
Water Res
The seasonality of bacterial quality of water in a tropical developing country (Sierra Leone)
J Hyg
Faecal coliforms and faecal streptococci in streams in the new guinea highlands
Water Res
Temporal variations of Escherichia coli concentrations in a large Midwestern river
J Hydrol
Assessment of drinking water quality using indicator bacteria and bacteriophages
J Water Health
Relationships between indicators, pathogens and water quality in an estuarine system
Water Res
Predicting coliform concentrations in upland impoundments: design and calibration of a multivariate model
Appl Environ Microbiol
Nowcast modeling of Escherichia coli concentrations at multiple urban beaches of southern Lake Michigan
Water Res
Beyond predictions: biodiversity conservation in a changing climate
Science
Waterborne transmission of protozoan parasites: a worldwide review of outbreaks and lessons learnt
J Water Health
A massive outbreak in Milwaukee of Cryptosporidium infection transmitted through the public water-supply
N Engl J Med
The Global Burden of Disease: 2004 Update
The ecology of climate change and infectious diseases
Ecology
Climate change and the distribution and intensity of infectious diseases
Ecology
The emerging and forecasted effect of climate change on human health
J Health Sci
Climate change and waterborne and vector-borne disease
J Appl Microbiol
Impacts of climate change on indirect human exposure to pathogens and chemicals from agriculture
Environ Health Perspect
Climate change, societal transitions and changing infectious disease burdens
Changing Climates, Earth Systems and Society
Refractory periods and climate forcing in cholera dynamics
Nature
Global health impacts of floods: epidemiologic evidence
Epidemiol Rev
Rainfall and outbreaks of drinking water related disease and in England and Wales
J Water Health
Global climate projections
Comparative risk assessment of the burden of disease from climate change
Environ Health Perspect
Human health
Health impact assessment of global climate change: expanding on comparative risk assessment approaches for policy making
Ann Rev Public Health
Climate variability and change in the United States: potential impacts on water- and foodborne diseases caused by microbiological agents
Environ Health Perspect
Climate change and infectious diseases in Europe
Lancet Infect Dis
Using satellite images of environmental changes to predict infectious disease outbreaks
Emerg Infect Dis
Health and climate change: a roadmap for applied research
Lancet
Global climate change
Healthy people 2100: modeling population health impacts of climate change
Climatic Change
Uncertainties associated with quantifying climate change impacts on human health: a case study for diarrhea
Environ Health Perspect
The association between extreme precipitation and waterborne disease outbreaks in the United States, 1948–1994
Am J Public Health
Cited by (111)
Precipitation and discharge changes drive increases in Escherichia coli concentrations in an urban stream
2023, Science of the Total EnvironmentLinking downstream river water quality to urbanization signatures in subtropical climate
2023, Science of the Total EnvironmentThe impact of heavy precipitation and its impact modifiers on shigellosis occurrence during typhoon season in Taiwan: A case-crossover design
2022, Science of the Total EnvironmentCitation Excerpt :As we know, heavy precipitation may facilitate the contamination of water source through increasing surface runoff, resuspension/water turbidity, the chance of sewer overflow and so on. ( Hofstra, 2011; Levy et al., 2016). Previous studies revealed that heavy precipitation significantly increase concentrations of human-associated bacteria (e.g. Escherichia coli) in rivers during event period or few days after events (Olds et al., 2018; Tornevi et al., 2014).
Flow exchange, energy losses and pollutant transport in a surcharging manhole linked to street profiles
2022, Journal of HydrologyA review on present and future microbial surface water quality worldwide
2021, Environmental Nanotechnology, Monitoring and ManagementCitation Excerpt :The concentration of pathogens in surface water probably increases after extreme precipitation events due to increased surface runoff, sewer overflow and re-suspension from sediments (Funari et al., 2012; Hofstra, 2011). Simultaneously, increased precipitation decreases the concentration in surface water due to dilution (Hofstra, 2011). Increased temperatures can also facilitate inactivation rate of pathogens (An et al., 2002).
Modelling rotavirus concentrations in rivers: Assessing Uganda's present and future microbial water quality
2021, Water ResearchCitation Excerpt :However, such studies mostly use historical diarrhoeal disease patterns. An integrated modelling approach combining socio-economic development and climate change impacts could provide new knowledge on future microbial water quality and the resulting diarrhoeal disease burden (Hofstra, 2011; Hofstra et al., 2019). Thus far, such studies are grossly limited.