As many as 10,000 migrant workers from south and south-east Asia die every year in the Gulf countries, according to a report by a group of human rights organisations.

More than half of the deaths are unexplained, said the report, and are commonly recorded as due to “natural causes” or “cardiac arrest”. But Gulf states are failing properly to investigate why so many migrant workers are dying.

The report, Vital Signs: The deaths of migrants in the Gulf, has been compiled by NGOs from Bangladesh, India, Pakistan, Nepal and the Philippines, and FairSquare Projects, a London-based migrant rights organisation.

Low-paid migrant workers in the Gulf are exposed to a series of risks to their health, including heat and humidity, air pollution, overwork and abusive working conditions, poor occupational health and safety practices, psychosocial stress and hypertension. Long hours of manual labour in searing temperatures can result in heat stress, which can lead to organ damage, the report said.

Despite widespread criticism of worker exploitation – notably in relation to Qatar’s preparations to host this year’s World Cup – the Gulf states have largely avoided structural labour reforms, and origin states have been unable to ensure proper protection for their nationals abroad.

The governments of the six Gulf countries did not respond to requests for comment.