The border between Afghanistan and Pakistan, already a key route for the heroin trade, is being used for a new type of smuggling - chlorofluorocarbons (CFCs).
CFCs come into Pakistan along with Afghanistan's heroin
CFCs - chemicals found in aerosols and refrigeration equipment and considered to be responsible for depleting the ozone layer - are mostly banned under the Montreal Protocol.
Production is still allowed for "basic needs production" for developing countries to use in air conditioning equipment and refrigeration equipment. But now, a black market for Europe-produced CFCs has sprung up in some Asian countries.
Salem Mutuwala, director of Karachi-based Symphony Limited - for whom CFCs are a small part of the country's legitimate business - told BBC World Service's One Planet that "at least 20 to 25" Pakistani businesses were trading in CFCs smuggled in as part of the heroin trade.
"We have pointed it out to the government and the government doesn't do anything," Mr Mutuwala added.
He said the main CFC smuggling routes were from Afghanistan - responsible for a great proportion of the heroin trade - or China.
"They come from over porous borders," Mr Mutuwala said.
"Some are Indian, and some are strange manufacturing brands that we seem to have coming now. They seem to be East European or Russian."
CFCs were found to be depleting the ozone layer in the 1980s
The CFCs came over in two main ways, he said.
Some were disguised in cylinders inside large containers - so many of them that it was impossible to check each one. But he said that the main way was through the heroin trade.
"During the Taleban time, the heroin trade had completely dried up, so all smuggling had stopped of all illegal trade," he explained.
"Now, after the liberation of Afghanistan, everything is coming illegally. There is so much money to be brought back.
"The heroin goes out, they have to bring something back to this area to sell back."
He said he had pointed out his allegations to the Pakistani Government, but he felt they were unwilling to look at them.
"If it wants to stop it, it will stop it - but I don't think the government wants to stop it," he said.
However, the Central Revenue Board in charge of customs in Pakistan denied it had received any information from Mr Mutuwala.
Chairman Ryas Malik said they were "completely unaware" of his allegations.
He added that they did not know of any seizures or detections of smuggled CFCs in the country.
The process by which CFCs are smuggled is sometimes a complex chain.
Companies in the West produce the chemicals for export to countries where they are required under the basic needs production provision.
Usually the CFCs are sold to perfectly legal brokers. However, these brokers may then pass them on to less legitimate businesses.
The Montreal Protocol is the most successful environmental treaty in history
In recent years, CFCs from an Atofina chemical plant in Bilbao have gone on the black market in Asia, and there are concerns at how they are ending up there - although Atofina themselves are not implicated.
"We've seen this in our investigations," Dr Ezra Clarke, from the Environmental Investigation Agency, told One Planet.
"Although the sale of CFCs from plants like this is perfectly legal, they're often sold to brokers or to intermediate countries.
"Through these, they can then be laundered on to black markets, where they can then be smuggled."
Investigations found that the intermediate countries most often used are Dubai and Singapore.
Mr Clarke said that to investigate what was happening, the Environmental Investigation Agency set up dummy company of brokers.
"Most of these chemicals from the plants where they're produced are then sent on to brokers," he said.
"The people that we were dealing with in Singapore were chemical dealers - they weren't the producers, they were middlemen."