The illegal exporting of waste carries a maximum two-year jail sentence
Brazil is to lodge a formal complaint that alleged illegal shipments of UK toxic waste have breached international conventions, its government has said.
Environment Agency officers and police in Britain raided three properties in the Swindon area of Wiltshire this week, arresting men aged 24, 28 and 49.
They want 1,400 tonnes of waste from 99 containers, said to include condoms and syringes, returned for inspection.
Brazil's president has criticised rich countries for sending rubbish abroad.
Luiz Inacio Lula da Silva said many of them claimed to be opposed to pollution.
But he added: "Who is going to recycle a condom? Who is going to recycle hospital waste?
"The only way out is for the containers to be sent back where they came from. We don't want to export our rubbish or to import the rubbish of others."
Brazilian diplomats are to lodge a complaint with the organisation in Geneva, run by the United Nations, which oversees international codes governing the transport of hazardous material.
It is based on the Basel Convention, which bans shipments of toxic waste from industrialised nations, Brazil's foreign ministry said in a statement.
It wants the origin of the containers traced and to find out how they ended up in three Brazilian ports - Santos, near Sao Paulo, and two others in the southern state of Rio Grande do Sul.
The Environment Agency said it could not confirm claims the shipping containers held a mixture of household and clinical waste.
It said it plans to search through the rubbish once it has been returned to the UK and ensure it is handled and disposed of properly.
The three men were released on bail on Friday, pending further investigations.
Their passports have been seized, but for legal reasons, they cannot be identified.
Head of waste Liz Parkes said the arrests marked "significant progress" in the investigation and that the agency was arranging for the waste to be shipped back to the UK.
She said: "The Environment Agency enforces the export of recyclable waste from England and Wales, and will not hesitate to prosecute any company or individuals found to have breached the strict laws on the export of waste.
"The United Kingdom has taken a strong global lead to stamp out the illegal waste trade, in order to protect people and the environment."
Waste can be sent abroad for recycling, but it is illegal to export it for disposal.
The maximum penalty for illegally exporting waste is an unlimited fine or two years in prison.