WATER REUSE FOR IRRIGATION - CAN DEVELOPING COUNTRIES AFFORD A TOLERABLE DISEASE BURDEN OF NO MORE THAN 10~(-6) DALY PPPY?

摘要

DALYs are a measure of the health of a population or burden of disease due to a specific disease or risk factor. It evaluates the time lost because of disability or death from diseases compared with a long life free of disability in the absence of disease. DALYs are calculated as the sum of years of life lost by premature mortality (YLL) and years of healthy life lost in states of less than fully health, i.e., years lived with a disability (YDL), which are standardized by means of severity weights, thus: DALY=YLL+YLD. WHO has established for wastewater use in irrigation (1) the same reference level of health protection as established for drinking water quality (2), i.e., the additional burden of disease from consuming water irrigated food should not exceed 10~(-6) DALY(Disability-Adjusted Life Years) loss per person per year (pppy). This level of risk means that a single additional case of disease may occur in a population of 1 million, during a life time (70 years). In a individual basis is equivalent to the occurrence of a mild disease during about 31,5 seconds. Such a restrictive risk is almost impossible to be attained in most developing countries which may not be able to afford the cost of wastewater treatment and of other protective measures, even for restrict irrigation. This paper presents proposals to adapt the reference level of risk to local technical, cultural, economical and social conditions of developing countries on the basis of a risk benefit approach.