Unsafe food kills more than 1.5 million people a year and causes cases of more than 200 diseases, research from the World Health Organization (WHO) has shown.

In its first major assessment of the impact of food contamination in more than a decade, the WHO found that unsafe food leads to around 885 million illnesses annually, costing the global economy an estimated $647 billion (£481.3bn) in lost productivity.

While bacteria, viruses and parasites are responsible for hundreds of thousands of deaths, it is actually toxic heavy metals that cause the lion’s share – some 73 per cent – of the fatalities, according to the report, which was published in The Lancet Global Health on Wednesday. 

“Food safety is not an abstract issue: it concerns every meal, every family, every day,” said Tedros Adhanom Ghebreyesus, the WHO Director-General.

“Unsafe food has always been a major public health concern, but until now we did not have a full picture of its colossal human and economic cost. These new estimates change the game.”

The research draws on data from 2000 to 2021.

It is the first time the WHO has published research on food contamination since 2010, when it estimated that around half a million people died from food-borne illnesses annually.

However, that report only examined the impact of bacteria, viruses and parasites.

And, while food safety standards have generally improved since the turn of the century, the impact of contamination with metals, particularly arsenic and lead, had not previously been included. 

Both metals occur naturally in soil but are also released into the environment through industrial processes like coal burning and metal smelting.

Over time, exposure can disrupt cellular function and damage organs, increasing the risk of cancers of the skin, lung, liver, and bladder among other tissues, irreversible brain damage, heart disease and kidney failure.

Rice is particularly vulnerable to heavy metal contamination because it is grown in flooded fields and readily absorbs contaminated water.

South-East Asia and Africa, where regulations on heavy metals in farming are far less stringent, are the worst-affected regions. It is thought that roughly 1 billion people are regularly exposed to heavy metals via their food. 

Bacteria also remain a major cause of food-borne illness and death. 

In 2021, around 250,000 people died after consuming food contaminated with harmful bacteria, mostly through diarrhoeal disease. 

Among the most common bacterial pathogens are Campylobacter and E. coli, which are frequently found in undercooked poultry, raw milk, and unwashed fruit and vegetables.

Listeria, which grows mostly in unpasteurised dairy products – products that have boomed in popularity in ‘wellness’ circles in recent years – poses a particular risk to pregnant women and newborns. 

While infections are usually mild in healthy adults, the bacterium can cause miscarriage, stillbirth and severe illness in infants. 

In 2021, Listeria was responsible for 5,280 deaths, the vast majority among newborn babies.

Parasites are another major cause of food-borne deaths, responsible for over 100,000 deaths a year. 

These organisms, which feed, grow, and multiply in the human body and can strip the body of vital nutrients, usually contaminate vegetables that have been fertilised with animal or human faeces. 

They can also be found in pork and beef, particularly when it is undercooked or has been stored at too high a temperature.

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