Long-term studies on health effects

Montebello Forebay - study 1

The first project that added purified recycled water to an underground aquifer was at Montebello Forebay in California. The aquifer has supplied drinking water for the greater Los Angeles metropolitan area since 1962.

A five-year toxicological study started in 1978 to determine if there were any possible health effects from the purified recycled water (Nellor et al. 1984). The study used bioassays to screen for mutagenic activity, because mutation plays an important role in the development of cancer. The study tested purified recycled water, storm water, imported surface water and unchlorinated and chlorinated groundwater.

The level of mutagenic activity was highest in storm runoff followed by dry weather runoff, recycled water, groundwater and imported water. Most of the mutagenic activity that was found appeared to be linked to the chlorination process.

Identification of the specific mutagens was not possible and since the concentrations were very low (parts per trillion levels), the authors were doubtful about any health significance. The results from this study were used in 1987 to support the increase of the annual quantity of recycled water that was used to replenish the groundwater.

Using ecologic epidemiological techniques, the health of communities in Montebello Forebay region of Los Angeles County utilising purified recycled water for drinking has been compared to that of matched control areas in Los Angeles County.

These studies have not demonstrated consistently higher rates of either general or specific mortality or disease in the populations receiving higher percentages of purified recycled water in their drinking water supply (National Research Council 1998).

The first epidemiological study was undertaken between 1969 and 1980. It examined mortality (all deaths, deaths from heart disease and stroke, deaths from all cancers, and deaths from stomach, colon, bladder and rectum cancers), various birth outcomes, incidence of stomach, colon bladder and rectum cancer, and some potential waterborne diseases.

There were no statistically significant differences in rates of cancer mortality or incidence in the communities using purified recycled water compared to the control communities.

Montebello Forebay - study 2

In the second study, in addition to the health outcomes investigated in the first study, deaths and incidence for a further four cancers (oesophagus, pancreas, liver and kidney) and more potential waterborne diseases were included.

No consistent relationship was found between exposure to water that contained purified recycled water and illness rates (National Research Council 1998).

Some significant differences in rates for some diseases were observed. In some cases, the rates were higher in areas receiving the greatest amount of purified recycled water. However, in other cases the rates were higher in areas receiving the lower percentages or none at all.

The investigators concluded that such differences were due either to chance (random variation) or other differences between the study populations that were unrelated to their use of water.

Another study examined adverse birth outcomes. The adverse birth outcomes were classified into 24 categories covering infant mortality, prenatal development and various types of birth defects (Sloss et al. 1999). The study examined the years 1982 through to 1993 and found no consistent association between residence in an area receiving recycled water and higher rates of these outcomes or any dose-response relationship between recycled water and the rate of these outcomes.

Namibia study

Research was also carried out in Windhoek, Namibia during the 1970s and 1980s (Isaacson and Sayad 1988). Windhoek is the only example of direct potable recycling, where purified recycled water is provided directly as drinking water to the customer rather than added into an environmental buffer where the recycled water is mixed with groundwater and water from dams.

The study compared the occurrence of diarrhoeal disease in residents from an area receiving recycled water with one that did not. No statistically significant difference was found over the full six years of observation.

For a two year period of the study, the incidence of diarrhoea among those receiving conventional supplies was actually statistically significantly higher than those receiving recycled water.

No adverse effects have been noted from consumption of water that consists of the highly treated recycled water.

In summary

In addition, Khan and Roser (2007), summarised studies examining the use of purified recycled water and the toxicological and epidemiological effects. They concluded that despite more than forty years experience, no clear deleterious health effects from planned indirect potable recycling schemes have been observed.

The references for the reports quoted above are:

• Isaacson, M., and Sayad, A.R. 1988. Health aspects of the use of recycled water in Windhoek, SWA/Namibia, 1974-1983. South African Medical Journal 73:596-599.
• Khan, S., and Roser, D. 2007. Risk assessment and health effects studies of indirect potable reuse schemes. Centre for Water and Waste Technology,University of New South Wales, Prepared for the Local Government Association of Queensland (LGAQ).
• National Research Council 1998. Issues in potable reuse: the viability of augmenting drinking water supplies with reclaimed water. National Academy Press, Washington DC.
• Nellor, M.H., Baird, R.B., and Smyth, J.R. 1984. Health Effects Study Final Report, County Sanitation Districts of Los Angeles County, Whittier, CA.
• Sloss, E.M., Geschwind, S., McCaffrey, D.F., and Ritz, B.R. 1996. Groundwater Recharge with Reclaimed Water: An Epidemiologic Assessment in Los Angeles County, 1987-1991. RAND Corporation, Santa Monica, California. Book available.
• Sloss, E.M., McCaffrey, R.D., Fricker, R.D., Geschwind, S.A., and Ritz, B.R. 1999 Groundwater Recharge with reclaimed water: birth outcomes in Los Angeles County, 1982-1993. RAND Corporation, Santa Monica, California. Read more.