Please suggest MCL for Th-232 in drinking water recommended by WHO, US EPA or AERB, India.
EPA has established a Maximum Contaminant Level (MCL) of 15 picocuries per liter (pCi/l) for alpha particle activity, excluding radon and uranium, in drinking water. Thorium would be covered under this MCL.
http://www.epa.gov/oerrpage/superfund/health/contaminants/radiation/pdfs/thorium.pdf
The WHO guidance levels for radionuclides in drinking-water are presented in Table 9.3
According to the Florida Department of Environmental Protection
There are two sources of radioactive contamination in drinking water. The first is naturally occurring radionuclides that are contained in the soil that water moves through. Some areas in Florida are susceptible to contamination from phosphate rich soils and rock. The second source of radioactive contamination comes from man-made sources. There is no known man-made contamination of drinking water in Florida.
Radionuclides found in drinking water are members of three radioactive series, uranium, thorium, and actinium and include the naturally occurring elements radium, uranium, and the radioactive gas radon. These contaminants may cause different types of biological damage. Radium concentrates in the bones and can cause cancers. Uranium can cause cancers in the bones and can have a toxic effect on kidneys.
The standards and rules governing radionuclides is currently under revision by the U.S. Environmental Protection Agency. Florida will adopt the new standards and rules when issued by EPA.
Radioactive Chemicals
Radionuclides found in drinking water are members of three radioactive series, uranium, thorium, and actinium and include the naturally occurring elements radium, uranium, and the radioactive gas radon. These contaminants may cause different types of biological damage. Radium concentrates in the bones and can cause cancers. Uranium can cause cancers in the bones and can have a toxic effect on kidneys.
The Standard
1. Naturally occurring radionuclides:
1.Combined radium-226 and radium-228: The Maximum Contaminant Level is 5 picocurries per Liter
2.Gross alpha particle activity including radium-226 but excluding radon and uranium: The Maximum Contaminant Level is 15 picocurries per Liter
2. Man-made radionuclides:
1.The average annual concentration of beta particle and photon radioactivity from man-made radionuclides in drinking water shall not produce a total annual exposure greater than 4 millirem/year.
2.Except for those radionuclides listed below, the concentration of radionuclides in paragraph (a) above shall be calculated on the basis of a 2 liter per day drinking water intake using the 168-hour data listed in "Maximum Permissible Body Burdens and Maximum Permissible Concentration of Radionuclides in Air or Water for Occupational Exposure," NBS Handbook 69 as amended August 1963, U.S. Department of Commerce.
Average Annual Concentration Assumed to Produce an Exposure of 4 millirem/year:
##Tritium in the total body - 20,000 pCi/L
##Strontium-90 in the bone marrow 8 pCi/L
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