Good points, use of all grey water systems increases risks. We do not know what all of the pollutants ARE in a given grey water, so how can we be sure we have adequately cleaned the water for appropriate use. Extensive experimental sampling, analysis, and assessment of toxicologic risk is essential, yet would still likely not recognize/remove all toxicants. Utmost testing, with scientific integrity, will be essential, and that is a tall order since it would probably be prohibitively expensive. We have created more than 85K largely new chemicals with which to contaminate water with by our uses, many of these have toxic effects, especially at chronic low dose accumulative levels that can be minute.We DO NOT, historically, do sufficient pollution assessment due to cost and difficulty of analysis. Not testing adequately is risky, currently not even possible, and funding to try to do due diligent science always gets short-changed. So, it comes down to 'best management practices' which are NOT best available practices at the scientific level. It seems like we should keep in mind: how much risk to our two year old child are we willing to risk for any given use of grey water?

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Good points, use of all grey water systems increases risks. We do not know what all of the pollutants ARE in a given grey water, so how can we be sure we have adequately cleaned the water for appropriate use. Extensive experimental sampling, analysis, and assessment of toxicologic risk is essential, yet would still likely not recognize/remove all toxicants. Utmost testing, with scientific integrity, will be essential, and that is a tall order since it would probably be prohibitively expensive. We have created more than 85K largely new chemicals with which to contaminate water with by our uses, many of these have toxic effects, especially at chronic low dose accumulative levels that can be minute.We DO NOT, historically, do sufficient pollution assessment due to cost and difficulty of analysis.

Not testing adequately is risky, currently not even possible, and funding to try to do due diligent science always gets short-changed. So, it comes down to 'best management practices' which are NOT best available practices at the scientific level. It seems like we should keep in mind: how much risk to our two year old child are we willing to risk for any given use of grey water?