For average adults, the excesses above the PTTI ranged from 20 to 40.

BBC: US rice imports 'contain harmful levels of lead'

Some samples exceeded the "provisional total tolerable intake" (PTTI) set by the US Food and Drug Administration (FDA) by a factor of 120.

BBC: US rice imports 'contain harmful levels of lead'

"According to the FDA, they have to be more than 10 times the PTTI levels (to cause a health concern), and our values were two to 12 times higher than those 10 times, " he told BBC News.

BBC: US rice imports 'contain harmful levels of lead'

That factor of 120 (12 times higher than 10 times the PTTI) alluded to by Dr Tongesayi is for children - most susceptible by virtue of age - among groups who eat rice more regularly than the average, such as Asians and Latinos.

BBC: US rice imports 'contain harmful levels of lead'