Almost 40% of the world’s waste ends up in huge rubbish tips, mostly found near urban populations in poor countries, posing a serious threat to human health and the environment.

From the air, the Mbeubeuss waste dump 12 miles north of Dakar in Senegal looks innocent enough. Now 45 years old and close to the Atlantic Ocean, it covers 175 hectares (432 acres) of an old, dried-up lake, is criss-crossed by tracks and roads, and you can see goats grazing and people working.

From the ground, however, Mbeubeuss is a malodorous, contaminated world of its own with towering hills of fly-infested waste shrouded in smoke from innumerable fires and its own small town of about 2,500 people, who live by sorting, burning and recycling what they can.

Mbeubeuss reflects growing consumerism in Senegal, expanding and changing along with the capital, Dakar, a city of 3 million people 25km (16 miles) away. As the west African country has become wealthier and the waste trade has been globalised, what is sent there and exported from it has also changed. Once it was mostly farm and organic household waste; now a tide of electronics and chemical waste, ranging from old fridges to computers, plastics and paint, arrives every day. From a few thousands tonnes a year sent there in the 1960s, the giant site now takes 475,000 tonnes of rubbish a year. But it is now so established that it has its own health centre, school, a credit and savings co-op and even religious shrines.

Mbeubeuss is one of 50 giant tips identified in a new atlas of the world’s biggest dumps, and is a contender to be named the biggest in the world. It can be compared to the giant Agbogbloshie dump in Accra, Ghana, which is one of the biggest in Africa and takes 192,000 tonnes of electronic waste a year; Awotan in Ibadan, Nigeria, which has become a breeding ground for disease; Dandora outside Nairobi, which covers 53 hectares and receives 730,000 tonnes of industrial, medical and farm waste a year; and the massive Bantar Gebang tip in Bekasi, Indonesia, which takes 230,000 tonnes. The grandaddy of them all may be the Deonar dump outside Mumbai, India, which opened in 1927. It is believed to have received about 17m tonnes of waste and now has 5 million people living within 10km of it. It has been formally closed, but still employs 1,500 people to scavenge for recyclables.

Finding the 50 biggest has proved difficult for the authors of the new atlas (pdf), who relied on crowd-sourcing 59,000 files from 25 countries. Some sites receive more waste than others each year; others are physically or historically larger or have more people working on them, or living within 10km. But all, say the authors, pose a serious threat to human health and water supplies, and all are located within or close to fast-growing cities in poor or low-income countries. According to the atlas, 18 are in Africa, 17 in Asia, two in Europe, eight in South America and five in Central America or the Caribbean. China, which is known to have some of the largest waste dumps, was not included because getting accurate statistics proved impossible.

“The world’s 50 biggest waste dumps are growing in size, are now affecting the health of over 60 million people and are polluting rivers, lakes and the oceans. But they should not be seen as local problems but a challenge to the world community, because they are located in very poor countries with no financial and human resources to manage them,” says Antonis Mavropoulos, one of the authors. “I really believe that the closure and rehabilitation of those dump sites and the development of sound waste management systems must be considered a global challenge and not a local one.”

According to the study, the 50 share similar problems. “Waste is dispersed widely, with no coverage or compaction, and they remain susceptible to open burning. They are open to all weathers … and often they are not engineered at all, with no leachate management and no landfill gas collection.

“They are poorly managed, if at all, without any controls on materials accepted or records kept, and no security. Waste pickers are often found collecting recyclables without any protection measures, or even living within dump sites, sometimes even scavenging for food leftovers. In this sense, dump sites pose significant health and environmental threats both to the people involved in the operations and to the wider general public living close by.”

According to the atlas, compiled by teams of academics and waste professionals on four continents, the 50 sites are all pollution and health timebombs. “The most common environmental issues … relate to surface water, groundwater and soil contamination from potentially toxic elements; air pollution from open-surface burning of materials, underground fires fuelled by landfill gas and gas leakage.

“The most common human health issues are diseases related to gastro-intestinal, dermatological, respiratory and genetic systems, and several other types of infectious diseases. The nearby populations experience diarrhoea, headaches, chest pains, irritation of the skin, nose and eyes, typhoid and stomach ulcers. People who work in dump sites are more prone to experience these diseases.”

Costas Velis, a lecturer in resource efficiency at the University of Leeds and one of the authors, says UN bodies and donor countries need to be alerted to the problems of open dumps. “All these sites are linked to very high levels of risks and potential harm. Simultaneous inhaling of fumes from burning plastics, contamination of aquifers, and release of substantial quantities of greenhouse gases takes place. Considerable urban populations live close to them.”

The authors estimate that nearly half the world’s population lacks access to even the most elementary waste collection and safe disposal services. The atlas reveals that almost 40% of the waste generated globally is disposed of unsafely in open dump sites. Most of these disposal sites can be found in low-income and developing countries, and are close to urban areas, posing a major threat to human health and the environment.

“The objective must be shutting down open dumps, even though this may pose short-term technical or cost problems,” say the authors. “It is recognised that there are locations where a lack of resources precludes the immediate closure of open dumps, in which case a controlled dumping approach must be taken. But this should be only an interim step to proper sanitary landfill practices.”