(FORTUNE Magazine) – The burning of so many oil wells at once is a unique event, and it may be years before the full extent of the damage is known. Such fires put out hydrocarbons similar to auto exhaust, soot, and toxic sulfur dioxide. Environmental engineers believe the impact will hit a large region, but not the whole world. Richard Small, a scientist at Pacific-Sierra Research Corp. in California, says the soot cannot spread around the globe and cause a cooling effect because, unlike volcanic ash, it is too heavy. But it may foul the atmosphere in Iran, Pakistan, and northern India. Much like industrial air pollution, it can aggravate respiratory ailments and pollute water systems. The fires are consuming daily about as much oil as Los Angeles does. First reports indicated that 460 million gallons of oil were dumped into the Persian Gulf by Iraqi soldiers. But Saudi officials now say satellite images & suggest that only 63 million gallons (about five times the Exxon Valdez spill in Alaska) went into the water and that as much as 30% of it was the result of allied bombing of Iraqi oil installations. That would make the spill the world's fourth largest. (Vying for the dubious honor of being No. 1 are spills from Iranian oil platforms attacked by Iraq in 1983 and a blowout on a Mexican platform in 1979; both may have disgorged 176 million gallons.) The Saudis have put protective booms around their desalination plants and are skimming oil with the help of at least eight nations. Much depends on wind and current. If a lot of crude drifts into tidal estuaries that nurture wildlife, the recovery could take years. One optimistic point: The oil will evaporate and degrade rapidly in the relatively warm Gulf waters. Roy Hann Jr., an environmental engineer at Texas A&M, thinks that most animal species will recover over time. The beast at greatest risk is the dugong, a large walrus-like mammal that is both slow moving and slow to reproduce. About 7,000 live in the Gulf.