Answer to Question #1946 Submitted to "Ask the Experts"

Trace amounts of alpha emitters (for example, ²²⁶Ra and ²¹⁰Po) and beta emitters (for example, ²²⁸Ra, ²¹⁰Pb) are found in all food products, irrespective of where they come from.

While it is expected that a product grown in an area with elevated levels of naturally occurring radionuclides in the soil will also have elevated levels of these radionuclides, it is not necessarily the case. It is also worth noting that only relatively small regions of the countries you mention have unusually high levels of radionuclides in the background. To be specific, the areas of interest are the states of Minas Gerais and Espirito Santos in Brazil and the state of Kerala and Ullal Beach near Managalore in India. For what it's worth, I have never hesitated to drink the Kingfisher beer produced in Kerala. In my opinion, the radioactive content of food is so low to begin with that any variations due to the country of origin are not worth worrying about.

With regard to the situation in Brazil, relatively little food is grown in Espirito Santos but the food produced in Minas Gerais does contain elevated levels of ²²⁶Ra and ²²⁸Ra.

Actual data is hard to come by. The following is the best that I could do. Note: one becquerel (Bq) is 1 disintegration per second. One kilogram (kg) is roughly equal to 2.2 pounds. One becquerel per kilogram (1 Bq/kg) = 0.027 picocuries per gram (0.027 pCi/g).

Drury et al. (1983) provides the following data that is specific to the high-radiation areas of India (Kerala) and Brazil.

State of Kerala, India:

Rice
Total alpha, 3 Bq/kg (dry weight)Total beta, 40 Bq/kg (dry weight)
⁴⁰K, 35 Bq/kg (dry weight)
²²⁸Ra, < 0.4 bq/kg (dry weight)

Tapioca
Total alpha, 16 - 22 Bq/kg (dry weight)
Total beta, 480 Bq/kg (dry weight)
⁴⁰K, 520 Bq/kg (dry weight)
²²⁸Ra, 11 Bq/kg (dry weight)

High-Radioactivity Areas of Brazil:

Kale²²⁸Ra, 34-1,100 Bq/kg (ashed sample)

Bean²²⁶Ra, 19 Bq/kg (ashed sample) compared with 2.6-17 Bq/kg for low-activity area
²²⁸Ra, 220 Bq/kg (ashed sample)
²²⁸Th, 52 Bq/kg (ashed sample)
Total Alpha, 2.6-30 Bq/kg (ashed sample)

Manioc
²²⁶Ra, 1,700 Bq/kg (ashed sample) compared with 39-59 Bq/kg for low-activity area
²²⁸Ra, 7,100 Bq/kg (ashed sample)
²²⁸Th, 1,800 Bq/kg (ashed sample)

Orange
²²⁶Ra, 540 Bq/kg (ashed sample) compared with 12 Bq/kg for low-activity area
²²⁸Ra, 6,100 Bq/kg (ashed sample)
²²⁸Th, 1,100 Bq/kg (ashed sample)

Squash
²²⁶Ra, 70 Bq/kg (ashed sample) compared with 0.9-5.6 Bq/kg for low-activity area
²²⁸Ra, 480 Bq/kg (ashed sample)
²²⁸Th, 310 Bq/kg (ashed sample)

UNSCEAR 2000 (Table 15 in Annex B) provides the following overall numbers for the ²³⁸U content in foods from India and the United States

Milk Products
India, 0.017 Bq/kg (wet weight)
United States, 0.0007 Bq/kg (wet weight)

Grain Products
India, 0.0074-0.067 Bq/kg (wet weight)
United States, 0.003-0.023 Bq/kg (wet weight)

Leafy Vegetables
India, 0.061-0.072 Bq/kg (wet weight)
United States, 0.024 Bq/kg (wet weight)

Root Vegetables and Fruits
India, 0.0004-0.077 Bq/kg (wet weight)
United States, 0.0009-0.0077 Bq/kg (wet weight)

References

Eisenbud M, Gesell T. Environmental radioactivity 4th ed. Academic Press; 1997.

Drury et al. Radioactivity in food crops. Oak Ridge National Laboratory publication ORNL-5963; 1983.

UNSCEAR 2000 Report of the United Nations Scientific Committee on the Effects of Atomic Radiation 2000.

Paul Frame, CHP, PhD