Betel nut powder has been shown by a recent study to cause cancerous tumours in lab mice, and scientists are now concerned that it could have the same effect in human consumers.

An immensely popular snack food throughout India, over 50 brands of betel nut powder are marketed as "paan masala", and serve as a convenient format of the traditional post-meal chew. Sales of over 50 brands of the powder amount to a US$200m industry.

Findings at weeks 16 and 56 of an 80-week study on 180 lab mice have raised questions however over the safety of the snack. The test, conducted by S K Nigam and colleagues from the National Institute of Occupational Health, Gujarat, observed mice on a diet containing 2% paan masala.

In a paper published in the Indian journal Current Science 2001 (pp 1306-1309), Nigam reveals that after 16 weeks there were no visible effects from the powder on the mice. After 56 weeks however, four out of 12 mice fed with ordinary paan masala had developed cancerous tumours. A worrying seven out of 12 who were fed paan masala with tobacco developed similar tumours in the lungs, liver, stomach, testes, ovary and adrenal glands.