Risk management drinking water

Box 10.2.5 Microbiological risk assessment a scientific basis for managing drinking water safety from source to tap... 

Hrudey, S.E., 2001. Drinking water quahty a risk management approach. Water, 26(1) 29-32. 

In the case of biological contamination, the identification of risk became obvious by experience, the risk assessment was made unambiguous by epidemiology, and the immediate and obvious effectiveness of the risk management decisions demonstrated their wisdom in the absence of elegant quantitative risk extrapolation models and projections of costs per case averted. Costs of water treatment and distribution became trivial relative to almost all other essential commodities, and in the public expectation the biological safety of drinking water became axiomatic. 

The fundamental and unresolvable element concerning adverse health effects and trace chemical contamination of drinking water is that in all but a few exceptional cases, three elements—risk identification, risk assessment by epidemiological data, and demonstrable risk management results—may never be available. 

Until very recently the risks associated with different types of chemicals such as food additives, pesticides, environmental contaminants and natural constituents of food were assessed and managed separately. However, a particular substance might fall into two or more of these categories and so the opportunity for simultaneous exposure might be overlooked. Furthermore, exposure to a chemical could occur through diet, drinking water, air pollution or dermal absorption. Aggregate exposure assessment aims to take all of the possible sources and routes of exposure into account in a realistic manner and thereby obtain a better overall estimate of risk. Initiatives have been set up in both the... 

Urbansky, E.T. and Schock, M.R. (1999) Issues in managing the risks associated with perchlorate in drinking water. J. Environ. Manage. 56, 79-95. 

The objective of this publication is to help users at national or local level to establish which chemicals in a particular setting should be given priority in developing strategies for risk management and monitoring of chemicals in drinking-water, The document will be useful to public... 

Identifying chemicals of concern to public health in drinking-water is based on the hazard to health of those chemicals and the probability of exposure. In many parts of developing countries, and in rural areas of some developed countries, water quality data are limited or nonexistent, making it difficult to determine priorities for risk management based on both criteria. In such cases, the priority for risk management must be determined on the probability of exposure alone,... 

As discussed above, for risk management purposes, priority should be assigned to specific chemicals on the basis of site-specific assessments. However, it is also important to pay particular attention to chemicals that have been found in many locations worldwide to present serious human health hazards due to exposure through drinking-water. These chemicals are mentioned below and are discussed in greater detail in the WHO Guidelines for Drinking-water Quality (WHO, 2004 WHO, 2006). 

Where public health agencies use pesticides for public health and vector control, it is most appropriate to refer to the agency responsible for vector control, to determine which chemicals are used and the management practices employed. Where the chemicals are applied in circumstances that affect drinking-water either directly or indirectly, the likely impact needs to be considered. However, there is a balance to be struck between the potential toxicity of the pesticides and the risks from insectborne diseases. 

A wide range of pesticides can potentially be found in drinking-water, usually at very low concentrations. Because chemical analysis can be difficult, common practice is to determine what substances are used in the catchment, and thus determine the monitoring and other risk management practices that are needed. However, the nature of pesticide use is such that concentrations in surface water may be very variable and intermittent Any monitoring will require careful planning if it is to generate useful data. Some pesticides are not very mobile in soil and, if found in water, they may be adsorbed to particulate matter. Many of the pesticides in current use are broken down rapidly in the environment. 

Chemical safety of drinking-water Assessing priorities for risk management... 

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