In Novi Sad, Serbia's second city, streets have been drenched with slimy, sooty rainwater since Nato's 1 May attack on oil refineries. Thirty oil tanks caught fire and continued burning until 11 May, emitting foul smoke into the air. Rains swept the sticky grime into the Danube. There has been no official explanation. Vast quantities of fire-extinguishing foam, needed to douse the 11-day blaze, posed a health and environmental hazard.
"The authorities are hiding the truth," said Dusan Vasiljevic, chairman of the opposition Democratic Party's ecology committee. "Even though we could benefit from knowing the risks for the Yugoslav population, they are doing this [hiding the truth] as they fear they will face pressure to do something."
In Pancevo, a town of 150,000 people, three big industrial plants were destroyed by Nato missiles - the city refinery, the Petrohemija oil products processing plant and the Azotara nitrogen-processing plant.
In the early hours after a strike at the nitrogen plant on 18 April, levels of the carcinogen vinyl-chloride monomer (VHM) were 10,600 times over recognised safety levels. Rains subsequently washed down the escaped VHM, poisoning land crops and fruit. Information was withheld, a Canadian television news crew was barred from the area and officials in Belgrade kept silent on the potential risks.
Simon Bancov, Serbia's environmental inspector, says the air pollution over Pancevo is now within safe limits, even though water and land is still affected. But even he is having trouble getting accurate data.
"Officials say that everything is all right," Mr Bancov says, "but there are various forms of pressure exerted on researchers not to publish the information. Those who do disclose sensitive data will probably be held to account [by the state]." He must make do with clues. "The ban on fishing best indicates that the water is polluted," he added.
Huge quantities of ammonium and ammonium based substances have been leaked into the Danube, already heavily polluted even before the bombing The Serbian Ministry of Agriculture, Forestry and Water Economy says local fish are a health hazard and has barred fishing on the Danube downstream from Pancevo, and on the Kolubara, Beljanica and Turija rivers.
Even more potentially deadly mudflows, bearing heavy metals and mercury, are seeping into these rivers. It is feared the poison will spread across southern Europe.
Mr Bancov has broken ranks, warning against eating fish, eggs and meat from the affected regions, with people advised to boil any water they want to drink.
Pregnant women are calling for abortions, though the Serbian Ministry of Information says that unborn foetuses are not at risk. But UN environmental teams have already sent a report to the secretary- general, Kofi Annan, warning of the dangers of "miscarriages, birth defects as well as incurable diseases of the nervous system and liver".
Some high-voltage transformers, hit during the bombing, used the highly toxic and cancerous coolant piralen, one litre of which can poison four million litres of water. Paediatricians around Belgrade are reporting numerous new and unexplained allergies among youngsters.
Milenko Vasovic is a journalist with the Institute for War & Peace Reporting: www.iwpr.net.