Were the discoveries of toxic chemicals in New York's Love Canal, and more recently at Missouri's Times Beach, isolated incidents? Or a prelude of more to come?
''Overall, I'm optimistic - partly because I think we'll be cleaning up a lot of these dump sites, and partly because we're not putting any more (hazardous waste) into the environment,'' says Jerry Hook, the director of Michigan State University's Center for Environmental Toxicology. ''Regulations on disposal have become much tougher over the last decade, and haulers of toxic waste have become subject to some very stiff state and federal regulations over the last two or three years.''
He cites the improvement in Lake Erie's water quality and the disappearance of DDT in fish after the chemical was banned as encouraging examples of what can happen when a determined effort is made.
Yet Dr. Hook and most other environmental experts concede that more of what he calls ''past mistakes'' may continue to be uncovered, even while new higher standards take hold. One reason, Hook says, is that the nation's ability to detect and measure toxic chemicals has improved dramatically over the last decade.
But some environmental experts argue that the cleanup job is so vast and the dollars available for it so limited that more seepage and surfacing of once-buried toxic chemicals are likely.
Neil Orloff, a professor of environmental law and policy at Cornell University, points out that the number of potentially hazardous toxic waste sites ranges from the industry's figure of 1,000 to the 10,0000 suggested by some environmental groups. He notes that the Environmental Protection Agency (EPA) has identified the 400 worst sites and pegs the cleanup cost at $25 billion to $44 billion. Yet even when fully funded, the EPA ''superfund,'' set up specifically for the job, would have only $1.6 billion to work with, he says.
''If we rely wholly on government, only a tiny fraction of these sites will be tackled,'' Dr. Orloff says. ''The best route to action is to have industry take the responsibility. In many cases we do have records of where hazardous wastes have been dumped and who the companies are. Just in the last six months the EPA has reached a few large settlements with such firms on cleanup efforts. But the question is still whether or not, in such consent decree settlements, industry puts up anywhere near the amount of money necessary.''
''There are literally thousands of toxic waste sites in the range from 'worst' to 'not quite so bad,' '' agrees Walter Lynn, director of Cornell's Science, Technology, and Society Program.
He says the EPA has received deservedly bad press. ''The agency faces a very large problem, but it has delayed in labeling the sites and using the superfund. We have the legal capacity to deal with the hazardous waste problem but no statute requires vigorous or even reasonable enforcement and compliance.''
Short of having more money to deal with the problem, a continued public focus on it and general awareness of the dangers can do much to reduce the impact and strengthen national determination to find a workable solution, environmentalists say.
''Certainly all the publicity given the problem has generated some rapid improvements in the current way we handle chemical wastes,'' notes Dr. Frank DeNoyelles, an associate professor of systematics and ecology at the University of Kansas. ''I'm less certain that positive steps are being taken on older dump sites. Enough time has passed that some of the materials we buried over the years are coming loose in their containers, literally seeping out of the dumps. I don't know of any solution (short of money for cleanup) other than identifying them and at least keeping people from building homes around them. All of the exposure given this problem has been good - it's better to know the dangers than not to know.''
''I think we've learned a lot of lessons from both Love Canal and Times Beach ,'' concludes Michigan's Dr. Hook. ''We've learned we must be constantly vigilant. . . . I think over the long term that we really are improving things and that we can have a positive impact on the environment if we continue on with the same degree of vigilance.''
This alertness has led to a number of experiments with the destruction of highly toxic waste - by burning or using bacteria to alter its composition. The process is very expensive. Says Hook, ''We won't see industry embracing these alternatives with open arms unless it comes under very strong pressure to do so - and the increased cost is sure to be passed on to the consumer.''