“The river is black. The air is full of dust. The rubbish we work with is full of disease. When you breathe, your lungs fill with poison. I am worried my baby girl will not be strong enough to survive here but we have no choice but to stay. There is no work for us back home.”

Li, 37, moved two years ago from Henan province with his wife Li Xiaoli to find work in the recycling industry in Lian Jiao, on the outskirts of the southern city of Guangzhou. Their baby daughter Xiao Yudian, whose name means Raindrop, has lived all her young life in their ramshackle brick house surrounded by junk.

The family is part of a wave of tens of thousands of migrant labourers from the poorest provinces of China drawn by wages of 800 yuan a month (100 US dollars) - four times what they earn for farm work in their home provinces.

Preparing imported plastic for use by Chinese factories has transformed Lian Jiao from a sleepy backwater into the world’s rubbish dump.

Here, household waste from around the world is shipped via Hong Kong to be recycled in a chaotic and haphazard industry that is contributing to the Pearl River Delta’s environmental deterioration and putting the health of migrant workers and their children in jeopardy.

Plastic wrappers are jet-hosed and doused in chemicals in nearby factory workshops, sending streams of dye and colourings directly into a heavily polluted tributary of the Pearl River.

Waste that is unfit for recycling - about 20 per cent of every 10-ton load - is trucked to overflowing landfills or burned - either in incinerators or in workshop yards, sending plumes of black smoke into the air.

Farming families in Li’s home province have been migrating to Lian Jiao to work for a decade, but most stay only for two or three years before returning.

“Often when people return, they are weak and they fall ill,” he said. “They have fevers, coughs and skin blemishes. Some of them develop cancer or lung disease and die within a couple of years of ending their work here even though they are young.

“No one knows the reason and there is no way to appeal for compensation or help. It’s not like being shot with a gun or run over by a car. The pollution kills you slowly and secretly.”

Looking down at the foul tributary that runs through the town, migrant worker Yang Yichun, 50, says: “This has to be the dirtiest stretch of river in the world. One day it is black, the next day blue, the next day yellow, the next day red, all because the workshops wash the dye from the plastic straight into it.

“If you breathe it in, it stings your lungs. If you stay too close to it for half an hour you will pass out because of the stench.”

When we visited Lian Jiao in early September, we found a newly arrived 10-ton consignment of mostly British household waste being picked over by workers and their children to recycle for use in Guangdong’s plastics factories.

The rubbish, which was carefully separated and placed into coloured bins in suburban driveways around the world, was shipped to Hong Kong in one of the container ships that used to return empty after bringing Chinese goods to the UK.

It was then taken by boat to the river port of Qing Yuan and transported in a convoy of ramshackle trucks into Lian Jiao, a 90-minute drive away.

The 14,500 kilometre journey from Britain to Lian Jiao is remarkably quick. Among the rubbish we found was a Tesco prawn and crayfish salad with a display-until date of June 12, Bernard Matthews turkey breast with a use-by date of June 26 and Sainsbury’s strawberries with a best-before date of June 24.

However, the destination of the rubbish would shock the western householders who believe they are helping the environment by separating waste. Trucks trundled in and out of the town’s dirt roads, the garbage dumped in a heap just 6 metres from the tributary that was also being fed with a bright red stream of plastic colouring from a factory pipe directly into the black water.  Around 2,000 small companies process the rubbish in Lian Jiao, paying around 3,000 yuan for a ton of plastic rubbish and then washing and chopping it up into small pellets to sell by the bag to plastics factories at a profit of around 500 yuan.

However, the recycling boom is contributing towards massive air and water pollution in Guangdong. Studies by Greenpeace have found that 55 per cent of the rain is acid in Guangdong - one of China’s biggest provinces with a population of more than 100 million - and 20 per cent of its rivers are heavily polluted.

Edward Chan, Guangzhou-based Greenpeace toxics campaigner, said it was up to consumers overseas to put pressure on recyclers to make sure their waste plastic was sent to places which were capable of handling it without causing environmental damage.

”In places like Lian Jiao they do not have those facilities. It is very primitive and it causes a lot of environmental harm as well as to the health of the migrant workers,” he said.

“People may separate their waste with the best of intentions and have no idea what happens to it after it leaves their home, but a lot of the environmental problems we have in Guangdong province are due to the imported waste.”

The Chinese government has tried to crack down on the import of waste and has heavily fined companies for importing waste material without permission in the past two years.

However, because of the huge demand for recycled plastic by Chinese factories and the seemingly limitless supply of low-paid rural workers willing to toil for long hours in appalling conditions, the recycling industry is continuing to boom.

Coughing heavily as he left his factory workshop, Huang Yintian, 45, from Sichuan province, said: “I work 14 to 15 hours a day, 30 days a month. The work is hard, dirty and dangerous. There is no time for rest.

“I work here because I am old, and I have no education and I have a wife and child back home to support. I haven’t been home for two years because I can’t afford to travel to see them. This is all I can do.”