Rain in the cistern; lead in the tap?

A new wrinkle in the Industrial Age's "acid rain" phenomenon may be affecting large numbers of people in the Northeastern United States. In addition to polluting lakes, rivers, and streams; killing fish; stunting plants; and corroding metal and wood, acid rain may be contaminating drinking water in ways only recently being detected.

Essentially, a study now under way at Penn State may provide the first direct evidence of a connection between the lead content of precipitation and increased lead levels in some drinking water supplies.

Those affected are some rural residents who depend on roof catchment/cistern water, because they live far from public supplies and have been forced by acid coal mine drainage to abandon more reliable groundwater supplies. Ironically, just as the mining of coal once tainted their groundwater supplies, today the burning of coal at distant power plants is contaminating precipitation, their sole remaining water source.

Such areas seem to be suffering from an "acid rain syndrome." They're feeling the effects of the complex, poorly understood phenomenon whereby chemical pollutants, emitted into the air by industries and autos, combine with developing rain and snow to form acids.

Carried by moving air masses into the upper atmosphere and thence to remote regions, both dry fallout and acid precipitation pollute the land below.

Cistern water supplies are highly vulnerable to such pollution. For unlike municipal supplies cistern water does not benefit from passing through soil, vegetation, and bedrock which filter out heavy metals and chemically alter the water to reduce acidity. In some such homes tapwater may have at times hazardous lead levels.

In Pennsylvania's rural Clarion County during the winter and summer of 1979, we analyzed 32 homes' cistern water. Preliminary results show high lead levels in the tapwater of five homes.

While we'll know more this fall when we complete our restudy of the original homes plus eight others, we appear to have found a definite link between the quality of precipitation and that of drinking water.

Because acid rain is reported to affect the entire region, we suspect similar situations exist for cistern users throughout the Northeast. Also, it's possible the same can be said for some municipal water systems. With this in mind, the federal Environmental Protection Agency (EPA), is sponsoring a survey of Northeastern municipal water supplies. They're looking for possible connections between acid precipitation and the heavy metals content of drinking water.

Our study seems to have found such a link for lead in cistern systems. Let's review the highlights of our preliminary findings.

First, we discovered that local precipitation was very acidic and corrosive, and contained high lead levels. In five homes, tapwater lead concentrations exceeded "safe" limits set by the Environmental Protection Agency. These families were warned not to drink their tapwater.

In the study area, bulk rainwater (precipitation plus dry fallout) lead concentrations averaged 24 micrograms per liter. Lead levels in snow averaged 5 .5 times higher than those in rain and 2.5 times more than the 50 micrograms per liter permitted by the EPA in drinking water.

Significantly, there has been much discussion about whether the 50 micrograms limit should be lowered. Some experts contend that may be too high, especially for inner city children who absorb unusually high amounts of lead, mainly from auto emissions and by chewing lead-based paint.

Such concern was expressed in a 1977 National Research Council report, Drinking Water and Health, which said: "Preliminary data suggest that the present limit of 50 micrograms per liter may not, in view of the sources of the environmental exposure, provide sufficient margin of safety, particularly for fetuses and young growing children. Although further studies will be necessary to arrive at a reasonable limit, it is suggested that the limits be lowered."

In our Penn State study, we found that cadmium concentrations were considerably lower than those for lead. In rainwater they averaged only 1.9 micrograms per liter, well below the 10 micrograms considered safe. However, in snow cadmium levels soared to a 17.2 microgram average. Unsafe levels of cadmium were not found in 1979 tapwater samples.

As for pH, it was very low in all 32 homes. On a pH scale where 7 denotes "neutral" and lower numbers higher acidity, average pH of rain ranged from 3.9 in summer to 3.68 in winter. The snow pH was higher (about 4.1). Total precipitation pH was well below the 6.5 minimum recommended for drinking water.

Thus, it's not surprising that in all the homes tapwater had a "very high corrosive potential." Using an index where numbers over 6 indicate increasing corrosiveness, bulk precipitation averaged 19.

We believe this corrosiveness aspect is crucial. For it partly explains why, in 59 percent of the homes, there was more lead in the tapwater than in the cistern water. Apparently, the water was so acidic that it corroded lead solder joints in the plumbing system, increasing the lead content of water coming through.

It's important to note that unpolluted rainwater itself is naturally soft or aggressive. However, the average pH of polluted rainwater in the Northeast is about 4.0. It's likely to be more corrosive than unpolluted precipitation.

How hazardous to health might such a situation be?

It depends on how much lead is being consumed by whom, for how long. Children and pregnant women would be the greatest concern.

How widespread might this situation be?

There's good reason to suspect that potential lead problems will be less severe in municipal systems than in roof/cistern setups, thanks to natural filtration of the former.

Nevertheless, some municipal systems still have problems, because the natural watersheds which supply their storage reservoirs yield an aggressive water. How much more corrosive such water might become due to acid rain is difficult to determine, due to the complexity of the soil, rock, and vegetation mix in most watersheds.

As for cistern systems, the problem is likely to be more severe, but also hard to assess. One of the reasons relates to another of our findings: that, when precipitation collected on roofs was stored for a time in cisterns, lead levels declined.

From what we can determine, sealers inside the cistern may have broken down, allowing some of the acidity to be neutralized in a chemical reaction with the cistern walls.

Another reason the extent of the problem is hard to pinpoint is that no one knows how many homes use cistern water systems. In Ohio it's estimated there are 67,000 systems. Similar data are unavailable for other states.

Finally, cistern water pollution may be a greater problem than we now believe , because other hazardous substances also may be present -- such as mercury, PCBs (polychlorinated biphenyls), and asbestos.

What can be done about the problems?

As far as we now know, there are two options. Various water treatment methods can be used and, where necessary, plumbing systems can be changed.

Unfortunately, such remedies are likely to be expensive. Few individuals are likely to attempt such procedures unless they believe their health truly is endangered.

Before this point can be resolved, many questions must be answered -- such as what levels of what pollutants are likely to find their way into cistern systems , how frequently will the pollution level in a typical home reach a danger point , and what is the fate of lead once it enters cistern storage?

These are some of the questions we're hoping to begin answering as we complete our Clarion County study this fall.