Risk Assessment in Water Recycling: EDCs as a Case Study

Abstract

During the last few decades, the focus on chemical pollution in water has been largely directed towards the well-known “priority pollutants” especially those displaying persistence in the environment. There are well established methods for assessing the risks posed by these chemicals and guidelines are usually available. At the same time there has been a transfer of hazard control critical control point or HACCP approaches from the food industry to water as in the most recent Australian Drinking Water Guidelines (ADWG 2004). This method is appropriate for known or better-understood hazards such as pathogens, but the available data for some substances for which there are no guidelines (eg. complex mixtures and 'emerging' contaminants such as hormones, drugs and personal care products) is limited. Consequently the methods for assessing risk are less well developed. In an era focussed on sustainability, the water industry is faced with the challenge of ensuring a sustained and safe supply of drinking water from sources of varying quality including recycled water for indirect potable reuse. In order to protect human health and the environment, risk assessment methods for these 'emerging contaminants' and a clear understanding of the risk are required. Some of the underlying science is complex and understanding the associated risks requires a thorough approach. Quantiative risk assessment methods based on mechanistic studies are being developed wordwide towards this need (Soto et al 1992; NIEHS 2002), however a curious situation has arisen in the last decade where the perception of risk has emerged as significantly greater than the risks suggested by the scientific data. This can significantly impact on decision-making and risk management. Endocrine disrupting compounds (EDCs), sometimes also known as hormonally active agents or endocrine modulators, are substances that can affect the endocrine system in animals including humans and fish. When people read or hear reports about effects in fish or other aquatic life they may wonder whether they should be concerned about similar effects in humans. There are two considerations here. 1. No studies to date have conclusively linked low concentrations of EDCs in wastewater to adverse health effects in humans (Damstra et al 2002), and; 2. The effects observed in fish and other aquatic organisms, and attributed to endocrine disruption can have other causes (Sumpter and Johnson 2005). This is not to say that the effects cannot be associated with EDCs, just that they may or may not be. We have demonstrated over the last few years that wastewater treatment can remove efficiently the majority of known EDCs before the water is recycled, at least for the treatment plants we have investigated (Chapman 2003; Leusch et al 2005, 2006a). However because cause and effect is difficult to demonstrate and it is nearly impossible to prove a negative, there remains a skewed perception of risk compared to the scientific evidence.