Rradiological assessment associated with vegetable farming in Cameron Highlands and Seberang Perai
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Date
2014
Authors
Aswood Alnafiey, Murtadha Shakir
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Abstract
The objective of this study is to detect and measure the natural radioactivity levels in selected vegetables that are very important for the protection of human health. Furthermore, the natural radioactivity levels in agricultural soil, irrigation water and fertilizer samples were measured. The samples were collected from Cameron Highlands, Pahang, which is the main source of vegetables in Malaysia and compared with the samples collected from land farms in Seberang Perai, Penang. This study was carried out using a high purity germanium (HPGe) to measure 226Ra, 232Th and 40K. Furthermore, the 238U and 232Th were measured by neutron activation analysis (NAA). RAD7 and CR-39 were used to measure the 222Rn concentration. The activity concentrations of 238U, 232Th, 226Ra, 222Rn and 40K found in all the samples were analyzed whereby the results varied based on the type of samples and the location. Based on the measured activity of 226Ra, 232Th and 40K, the hazard indices such as, radium equivalent activity, absorbed dose rate, annual effective dose, and ingestion dose as well as internal and external indices were calculated in the samples to assess the health risk. All the vegetable samples, agricultural soil and irrigation water have radium equivalent activities within the safety limit 370 Bq kg-1 reported by OECD. Whereas, the fertilizer samples were below the safety limit reported by OECD, except muriate potash, phosphorus and potassium samples. The absorbed dose rate, internal and external indices in vegetables and irrigation water were found below the safety limit reported by UNSCEAR. In the soil samples, the dose is slightly over the Malaysia average 92 nGy h-1 and about two times over the
world average 59 nGy h-1 reported by UNSCEAR. The annual effective dose was
found as in the individual countries within the range 0.3 - 0.6 mSv that was also
reported by UNSCEAR. The values of Hin and Hex were lower than the unity. The
annual ingestion dose of the natural radionuclides from vegetables was found to be
within the recommended values 250 - 400 Sv as given by WHO. The radon
concentration found in agricultural soil and fertilizer samples were within the safety
limit. The radon concentration level in water samples was below the safety limit
reported by EPA which recommended maximum contaminant level of 11.1 Bq L-1.
Finally, the transfer factors of 226Ra, 232Th and 40K from the soil to vegetables were
found in this order: 40K > 226Ra > 232Th. A strong correlation between 226Ra and
222Rn was found in this order: Fertilizers > agricultural soil > irrigation water.