ON January 14, 2010, The Daily Star reported an increase in the accumulation of arsenic levels in the topsoil of agricultural lands that are irrigated by arsenic-rich groundwater. The article referred to a recent study by Professor Badruzzaman and Professor Ali (both of Buet). In their study, the professors reported that paddy grown on lands that have been irrigated by arsenic-rich groundwater contain up to 0.3 milligrams (300 micrograms) of arsenic per kilogram of paddy. A relevant but unanswered question is whether this level of arsenic in the grains is a health threat. While the Daily Star article is rather ominous in its tone, some analysis based on WHO and FAO data leads to a less threatening conclusion.
World Health Organization (WHO) and Food and Agricultural Organization (FAO) have been concerned with arsenic for several decades now. In 1967, Who established the maximum allowable daily load (MADL) of arsenic as 50 micrograms/kg of bodyweight/day. Several years later, these initial limits were significantly revised by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The revision declared provisional tolerable weekly intake (PTWI) of 15 micrograms/kg of bodyweight/week for inorganic arsenic (the harmful form of arsenic generally found in the ground). Note that this translates to arsenic intake of just 2.14 micrograms/kg of bodyweight/day. This stringent limit set forth by JECFA remains in practice even now. It should also be noted here that the minimum lethal dose of arsenic is roughly 1,000 micrograms/kg of bodyweight/day.
With the different arsenic intake limits available, we are in a position to examine whether arsenic consumption through rice is a serious threat. Let us assume that the average Bangladeshi man weighs about 60 kg and the average woman weighs about 50 kg. Then, following the most stringent arsenic intake limit set by JECFA, we have PTWI of approximately 900 micrograms (128.57 micrograms per day) and 750 micrograms (107.14 micrograms per day) of arsenic for a man and a woman respectively. If we adhere to the 1967 MADL limit, MADL is 3,000 micrograms for a man and 2,500 micrograms for a woman. The minimum lethal dose would be about 60,000 micrograms for a man and 50,000 micrograms for a woman.
It is estimated that for average Bangladeshis, about 70% of daily caloric intake comes from rice. Assuming that a woman of 50 kg weight consumes 1,500 calories and a man of 60 kg weight consumes 2,000 calories, the woman will have consumed 1,050 calories in rice and the man will have consumed 1,400 calories in rice. Since 1 gram of rice produces 4 calories, we can deduce that the woman will have consumed 262.5 grams of rice and the man will have consumed 350 grams of rice per day.
If the rice comes from paddy that has 300 micrograms of arsenic (the highest amount found by Professors Badruzzaman and Ali), then the arsenic consumption for our hypothetical 60kg Bangladeshi man is 105 micrograms and for our hypothetical 50kg Bangladeshi woman is 78.5 micrograms per day. These numbers are below even the most stringent arsenic intake limits established by JECFA. Of course, the MADL and the lethal levels are nowhere near the arsenic consumed through rice that came from paddy registering the highest levels of arsenic in the study.
Although these levels of arsenic are below the PTWI established by JECFA, the health risks involved with considerable consumption of arsenic should not be neglected. As identified by the WHO, the symptoms associated with arsenic poisoning are abdominal pain, vomiting, and bloody "rice water" diarrhea. Also, arsenic is classified as a carcinogen and may cause cancer of the skin, lungs, kidneys, and bladder. The health risks of arsenic are greatest for children, elderly, and those whose immune systems are compromised due to disease.
In Bangladesh, arsenic intake occurs mainly through drinking arsenic-rich water. Reducing arsenic content in drinking water is an effective way to keep arsenic intake in check. Compared to the threat of arsenic-rich drinking water, the presence of arsenic in irrigation water (because it passes on to food grains) seems less threatening. Being aware of arsenic concentration in water is necessary, but a trace amount of arsenic in paddy is perhaps not as alarming.

Alexis Mosquera is a registered nurse and Dr. Noushi Rahman is an Associate Professor of Management.