As many as 100 million people worldwide are facing slow poisoning and risk of death from arsenic in their drinking water and food supply.
That is the conclusion of scientists at the CRC for Contamination Assessment and Remediation of the Environment (CRC CARE) following a global review of the health effects of arsenic on people in affected countries.
"This is probably the worst mass poisoning event in history – and in many cases it is preventable," says CRC CARE managing director Professor Ravi Naidu.
"The bad news is that it is spreading around the world in the expanding global food trade, exposing millions more people to risk."
Arsenical poisoning is worst in Bangladesh, where an estimated 35-77 million people are at risk from drinking groundwater contaminated by naturally-occurring arsenic. Another 6 million are at risk in West Bengal, India. However, numerous cases have now been reported from China, Chile, Cambodia, Laos, Burma, Pakistan, Nepal, Vietnam, Taiwan, Iran, Argentina, Finland, the United States and several other Indian States.
Some groundwaters in Australia are also known to be contaminated with arsenic, and the landscape contains ‘hot spots’ from its former widespread use as a insecticide to protect livestock and crops nearly a century ago, Prof. Naidu says. Concentrations of arsenic are also sometimes associated with old gold diggings and old rail tracks.
Besides being known to cause cancer of the skin, lung, bladder, kidney, liver and uterus, arsenic is also linked to several skin diseases, nerve disorders, diabetes, lung disease, heart disease, suspected birth defects, liver and blood disorders, according to a review by Mohammad Rahman and Prof. Naidu.
"At high doses arsenic is a known carcinogen and can cause heart attack and diabetes. Much less clear are the effects of prolonged exposure to low doses in water and food, and there needs to be a lot more research done globally to find out," says Dr Rahman.
"The US National Research Council estimates that drinking a litre a day of water containing 50 micrograms of arsenic would result in 13 deaths from cancer per thousand people, but we can only guess the effect for doses greater or lower than this over time."
Also diet seems to play a crucial role, he says. Well nourished people appear more resistant to the effects of arsenical poisoning, whereas the poor and hungry experience its symptoms far more acutely.
Work by CRC CARE scientists has revealed that not only drinking the water is dangerous. Rice and vegetables may also take up arsenic when grown in contaminated water and small amounts may pass through the food chain via meat and milk to people. Rice or vegetables boiled in the contaminated water can also take up arsenic during the cooking process.
"In Bangladesh, arsenic levels in rice can range as high as 1770 micrograms per kilo and in vegetables as high as 3990 micrograms," Dr Rahman says. "A level of 1000 micrograms per day is enough to produce the skin lesions of arsenicosis within a few years."
"Also, foodstuffs imported into the United Kingdom from Bangladesh were found to contain up to 540 micrograms per kilo of arsenic."
The World Health Organisation recommended maximum level for arsenic in drinking water is 10 micrograms per litre.
Professor Naidu says this finding suggests that with supermarkets now sourcing their fresh fruits, vegetables and grains worldwide, arsenic poisoning has become a global problem exposing millions of consumers in countries not significantly affected by contaminated groundwater.
Ironically, levels of arsenic are found to be highest in leafy green vegetables, regarded the world over as a desirable and healthy food and which contains many vital nutrients, such as iron.
"Due to the growth in the globalised food trade, the issue of arsenic poisoning is no longer confined to those countries with contaminated groundwater. Many consumers in the developed world may be, to some degree, at risk. This increases the international urgency of overcoming it."
Professor Naidu says the arsenic poisoning calamity is preventable in most areas with a combination of education and appropriate technologies, such as the use of domestic rainwater harvesting and simple devices which absorb arsenic from drinking water. However these do not solve the larger issue of crops grown on contaminated water, for which the only solution is to develop improved surface water irrigation and reduce reliance on groundwater.
"Australia has significant skills in the management of contaminated soils and water and we should be stepping up our efforts to help those countries most affected by arsenic poisoning. At the same time we will be helping to protect our own consumers."
(Source: Peter Martin: Contamination Assessment and Remediation of the Environment: February 2008)