Rice tablet poisoning: A major concern in Iranian population

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We have read with interest the recently published article by Shadania et al, entitled ‘A retrospective 7-year study of aluminum phosphide poisoning in Tehran: Opportunities for prevention’. As this is a common poisoning in Iran, we appreciate the opportunity to read about this poisoning. There are two kinds of rice tablets which are used in Iran to protect stored grains and rice from rodents and other household pests. Aluminum phosphide (ALP), a fumigant which releases toxic phosphine when it comes into contact with moisture, is the most common type of rice tablet. It is marketed as 3-gm tablets (Phostoxin Celphos, Quickphos and Phostek). Another tablet used for this purpose is a herbal product also known as Rice Tablet (Figure 1). Although public sale of ALP tablets is banned in Iran, it is still available. Both rice tablets are indistinguishable to the lay person and are used often for suicide purpose. The points which help in differentiating the two are change in appearance of the tablet when exposed to air (Figure 2) and its garlic-like odor. The herbal rice tablet is potentially harmless as it contains only botanical products unlike ALP, which releases phosphine. When a poisoned patient is brought to the emergency room it is difficult to differentiate the two. However, from looking at the container brought by patient’s relatives and clinical features, it is possible to differentiate the two. Further a silver nitrate breath test can be performed to detect phosphine. The mortality rate in ALP poisoning is high, resulting in 55-70% mortality in different studies. The blood pH was higher in this study (mean 7.3) unlike the study by Singh et al. where of 195 patients, 180 blood pH <7.3 with 62 having pH <6.9 in the study by Shadnia et al mortality was 31%. It is quite possible that in this study mortality was lower due to ingestion of exposed tablets which have lower phosphine content. As soon as ALP comes in contact with moisture, some phosphine gets released with resultant lower phosphine content in these exposed tablets and when someone ingests these tablets, lesser phosphine will be released in gut, resulting in less severe toxicity. A recent report from India suggests that a change in formulation from tablet to granulated powder has lead