Washington — In the wake of India's tragic poisonous gas leakage, experts in the United States say prospects for toxic spills here are very low but not inconceivable, given the often-cited risks of living in a modern, industrial society.
''It could happen here. Why couldn't it?'' says Jeff Leonard, a senior associate at the Conservation Foundation, an environmental organization. ''But the chances of those errors occurring are much less here. We're much more cognizant of the dangers of chemicals.''
The exact chain of events that caused a cloud of methyl isocyanate gas to seep out into the densely populated Indian neighborhood, killing at least 1,600 people and possibly affecting about 50,000 others, are still unknown. Initial investigations reveal that pressure in an underground storage tank rose suddenly , and the poisonous gas escaped through a safety valve, overwhelming a scrubber that was supposed to neutralize it.
But US experts are curious as to how the gas developed in the first place, since the chemical is stored in liquid form. They wonder how such a large quantity escaped before safety steps were taken.
''A number of things about this don't make any sense,'' says John Jacobus, a professor of chemistry at Tulane University. ''Apparently nobody in the plant itself was injured, for instance. Why?''
Many US experts in toxic substances say they believe some sort of serious human error must have been a major cause of the disaster. Warren Anderson, chairman of Union Carbide, owner of the plant in question, said Tuesday he was leaving immediately for India to determine the cause of the accident.
Safety standards at the Union Carbide plant in Bhopal, India, are no different from those in the company's US plants, says company spokesman Thomas Sprick. Other experts agree that it is unlikely that this disaster is an example of a US company sending operations overseas to escape safety and health regulations.
But when a company's chain of command stretches over several continents, it's difficult to make sure safety procedures are followed strictly - especially in a culture that does not fully understand the hazards of modern chemicals, says Mr. Leonard, who has just written a book on US chemical companies overseas.
''They didn't have a respect for the dangers involved,'' says Leonard of a number of countries he visited in writing his study. ''In Mexico, where they recently had that (natural gas) explosion, people are now saying, 'We noticed the smell of gas for a long time.' In the US, that would be picked up on quickly.''
The tragedies in both India and Mexico, Leonard notes, were intensified by the fact that the affected neighborhoods were dense and growing fast. People were ''literally living up against the walls of the plant'' in Mexico.
The substance that escaped from the storage tank at the Union Carbide-owned plant in India (methyl isocyanate) is widely used in preparing insecticides as well as in making some plastics and polyurethane foams.
The gas is used as an ''intermediate'' - a building block - to make other chemical products. By itself it is highly toxic - roughly 50 times more so than chlorine, according to Robert Alberty, a chemistry professor at the Massachusetts Institute of Technology.
When combined with other chemicals to form a pesticide, however, the gas changes its nature and ceases to exist.
Union Carbide's plant in Institute, W.Va., is the only place in the US where methyl isocyanate is produced. (Company officials say production of the chemical has been halted in this country while the causes of the India leak are investigated.) It is then shipped to another Union Carbide plant near Woodbine, Ga., where it is used in making the popular pesticides known as Sevin and Temik.
George Hannaford, city administrator in Woodbine, says most people are glad to have Union Carbide in the area as a major employer.
''I have nothing but praise'' for the chemical company, Mr. Hannaford says.
County officials, however, plan to meet with the managers of the Woodbine plant soon, in response to the Indian accident.
County and school officials contacted by this newspaper were not aware of any emergency evacuation plans to be used in the event of a leak at the plant, which is in a sparsely populated area.
In the US, regulation of dangerous chemicals such as methyl isocyanate is far from comprehensive. Controls focus on end-use products rather than intermediate chemicals, and on disposal of substances that classify as hazardous waste.
The particular locus of trouble in India - storage tanks for chemicals - is still unregulated in this country. ''Those tanks are all over the place in this country, both above and below ground,'' notes Joel Hirschhorn, a toxics expert with the Congressional Office of Technology Assessment.
There is a law governing tanks - it was just signed last month by President Reagan, in the form of amendments to the Resources Conservation and Recovery Act (RCRA). But the detailed regulations that make up the meat of the law must still be written by the Environmental Protection Agency (EPA).
''Complete regulations may be several years away,'' says EPA spokeswoman Robin Woods.
The RCRA amendments were pushed by members of Congress and environmentalists concerned that leaking tanks are contaminating ground-water supplies. In California's Silicon Valley, for instance, officials have identified 142 plumes of pollution leaking from chemical storage tanks.
That doesn't mean that chemical tanks in the US are necessarily potential bombs. Within manufacturing plants, the handling of chemicals is regulated by the Occupational Safety and Health Administration.
The Toxic Substances Control Act (TOSCA) gives federal regulators broad powers to control the manufacture and use of such dangerous chemicals as polychlorinated biphenyls, or PCBs. It also requires the EPA to keep an eye on new chemicals that come to market, and conduct toxicity studies of the some 55, 000 chemicals already in daily use in the US.
TOSCA is a complex law, however, and environmentalists charge that the EPA has dragged its feet in carrying it out. Only a handful of substances are now regulated under the statute (''in the single digits,'' sighs an EPA official). Little information on the toxicity of chemicals in use has been compiled.
Pesticides in the US are regulated under yet another law, the Federal Insecticide, Fungicide, and Rodenticide Act. And dangerous substances that have passed their useful life are regulated under various hazardous-waste laws, including the Superfund for emergency cleanups.
An EPA official notes that methyl isocyanate is on agency lists as a regulated hazardous waste.
But environmental regulation might not have been able to head off the Indian accident, some experts say.
''It's hard to know whether regulations would have made a difference,'' says Frances Irwin, a Conservation Foundation expert on environmental law.