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bacteria and parasites. Congress acted upon evidence that half of the thousands of Americans who become sick each year from waterborne illnesses were infected by inadequately treated groundwater. Another problem is lead, which accumulates in the body. High levels can cause damage to the brain, kidneys, nervous system and red blood cells. EPA recommends that if people have lead in their water or pipes, they should use cold water for drinking and cooking, and flush the pipes before drinking it Although lead is not often found in groundwater. it was discovered to be prevalent in faucets fed by AGRICULTURAL POLLUTION The four major sources of agricultural pollution are fertilizers, pesticides, animal waste and irrigation runoff. Some pollution problems are not unique to urban or rural areas. Nitrogen, for instance, can result from failing septic systems and over-fertilized landscapes, including golf courses, as well as from dairies and intensely farmed areas. Nitrate pollution. according to the state Department of Health Services (DHS) and the State Board, is responsible tor the closure of more water supply wells than any other contaminant - including 800 wells in southern California, 130 wells in the San Joaquin Valley. 60 wells in the Salinas Valley and three wells in the southern Sacramento Valley. The most common sources of nitrogen are fertiliz- ers, manure and waste ponds. In the soil, microor. ganisms can convert nitrogen into nitrate, which can be a health threat at certain levels. Arnong the prob- lems is the potentially lethal 'blue baby syndrome" (methemoglobinemia) in which nitrate limits the ability of newborn infants' blood to transport oxygen. Nitrate from fertilizers is most common where high- value plants that demand a lot of water are grown in sandy soils commonly found in the San Joaquin, Salinas, Santa Maria and Santa Ynez valleys and the Oxnard plain. Just as California has the largest agricultural harvest of any state, it has the highest use of farm chemi- cals - and a consequence is widespread pesticide contamination of groundwater. According to the University of California, pesticides or their breakdown products have been found in nearly 4,000 wells - Including more than 2,000 private domestic wells and more than 1,000 public water supply wells. (This is a small percentage of the total number of wells in California, most of which have not been tested.) 16 groundwater. In many cases the problem was thought to be pump parts constructed with brass that contained lead. The submersible pumps sat in the water at the bottom of the well. leaching lead into the water, which was then pumped to the surface. Lead also poses a problem for people who live in homes constructed with lead pipes or with copper pipes that were soldered with lead. In both instances, the problem was more serious in regions with acidic water that is more corrosive. Both construction techniques are now illegal. Municipal supplies are tested and corrosion controls can reduce the threat. One of the worst pesticide pollution problems stems from DBCP, dibromochloroprcpane, a potential human carcinogen widely used as a soil fumigant from 1955 until it was banned in 19r. The USGS says DBCP has been found in t1e groundwater of every county in the San Joaquin Vai'sy. DBCP was detected in 2,522 of 8.190 private ane r. 'blic water supply wells that were sampled betw.... '3n 1979 and 1984. According to the University at California, Berkeley. School of Public Health, 875,000 people in Califor- nia are at risk of exposure to DBCP through contaminated public drinking water supplies. In Fresno, 41 percent of the wells have detectable levels of DBCP, and 25 percent of those wells have been closed because concentrations of the pesticide exceeded drinking water standards. Fresno and several other valley communities took legal action against the makers of the chemical and have successfully recovered tens of millions of dollars spent to clean up aquifers or develop alternative water supplies. Other pesticides have created similar problems. Some of the contamination resulted from the normal application of pesticides and some from pestlcides spilled while being transported. mixed. loaded. disposed of and stored. In the Central Valley. 10 pesticide-related Superfund sites have been declared. On the west side of the San Joaquin Valley, irrigation runoff is a problem. Here, irrigation water can become trapped in a shallow aquifer by a layer of clay close to the surface, a condition known as "perched water." In those areas, the shallow aquifer has to be drained into order to keep the land productive, which creates a dilemma of how and where to dispose of the tainted runoff.