Safety of community drinking-water and outbreaks of waterborne enteric disease: Israel, 1976-97.

Waterborne disease remains a major public health problem in many countries. We report findings on nearly three decades of waterborne disease in Israel and the part these diseases play in the total national burden of enteric disease. During the 1970s and 1980s, Israel's community water supplies were frequently of poor quality according to the microbiological standards at that time, and the country experienced many outbreaks of waterborne enteric disease. New regulations raised water quality standards and made chlorination of community water supplies mandatory, as well as imposing more stringent guidelines on maintaining water sources and distribution systems for both surface water and groundwater. This was followed by improved compliance and water quality, and a marked decline in the number of outbreaks of waterborne disease; no outbreaks were detected between 1992 and 1997. The incidence of waterborne salmonellosis, shigellosis, and typhoid declined markedly as proportions of the total burden of these diseases, but peaked during the time in which there were frequent outbreaks of waterborne disease (1980-85). Long-term trends in the total incidence of reported infectious enteric diseases from all sources, including typhoid, shigellosis, and viral hepatitis (all types) declined, while the total incidence of salmonellosis increased. Mandatory chlorination has had an important impact on improving water quality, in reducing outbreaks of waterborne disease in Israel, and reducing the total burden of enteric disease in the country.

Water quality, waterborne disease and enteric disease in Israel, 1976-92.

Israel experienced a large number of waterborne disease outbreaks between 1975 and 1985, followed by a steep decline in the period 1986-92. Large-scale community waterborne disease outbreaks occurred primarily in the late 1970s, and in 1985 (the Krayot, four small towns neighboring Haifa), but substantial outbreaks occurred as late as 1989, with 4 during 1986-90, and 1 during 1991-92. New water standards, including mandatory chlorination of all community water supplies, came into effect in late 1988. Water quality, as monitored by the Ministry of Health, showed a marked improvement even when measured by the more stringent standards of the 1988 regulations. Long-term trends in the total of reported enteric infectious diseases from all sources, including typhoid, hepatitis, Shigella and Salmonella in Israel are examined. Typhoid, which has been declining since the 1960s, peaked in 1985 with the large waterborne disease episode of the Krayot. Shigella and total hepatitis incidence increased slowly up to the mid-1970s, followed by large increases during the 1975-85 period, then by a rapid decline up to 1991. Shigella, from childhood contacts in kindergartens, increased in 1992. Salmonella incidence continues to increase steadily. Mandatory chlorination and more stringent water standards have had an important impact on water quality and on waterborne disease outbreaks in Israel. Empiric evidence suggests that improving water quality may also be a factor in the changing patterns of some enteric diseases and the total burden of enteric disease in Israel.

Deterioration of Jerusalem limestone from air pollutants; field observations and laboratory simulation.

Samples of Jerusalem limestones were exposed to high levels of common air pollutants (SO2, NO) in the presence and absence of hydrocarbon, water vapor and ultra-violet light. After exposure, the outer layers were shaved off and analyzed for sulfate and nitrate. The results revealed that even after one day of exposure significant concentrations of CaSO4 and Ca(NO3)2 could be detected in the external 40 µm layers. Sulfate formation was found to relate very strongly to relative humidity with nearly undetectable production at humidities below 10%. Nitrate formation was found to relate to UV light and to a limited extent to the presence of hydrocarbon but was unchanged at different humidities. Surface samples were taken from different sites of the old city wall and were also analyzed for the same substances. The data showed that the concentrations of especially CaSO4, and to a limited extend Ca(NO3)2, measured at various points along the city walls were higher than the expected values extrapolated from laboratory simulations. The elevated pollution content may be explained in part due to the deposition of transported ions, especially sulfate, onto the stone surface. It was concluded that although air pollution may not cause any structural damage in the foreseeable future it definitely deteriorates the fine details of the ancient monument.