60 µg/l uranium in drinking water safe: Nuclear safety watchdog

The earlier version of BIS safety standards for drinking water — last updated in 2012 — did not specifically mention uranium contamination. It had safe limits for all radiological substances, and the limits were defined not in terms of their concentrations but the radioactive decay undergone by the substances per second per litre of water. This limit for all alpha-particles emitting radioactive substances such as uranium was set at 0.1.

The BARC study, published in international journal ‘Environmental Science and Pollution Research’ has argued that compliance to the new BIS standards would entail additional costs in purification, while having no health benefits. Excessive uranium content is linked to diseases related to kidney, and even cancer.

The BARC study, meanwhile, cited several medical researches, including those conducted by the WHO, to argue that small concentrations of uranium in drinking water pose no threat.

“While high-specific activity (rapidly decaying) soluble uranium compounds have been demonstrated to induce bone cancer in experimental animals, through injection or inhalation, no evidence of cancer has been found in animals consuming either insoluble or soluble uranium compounds,” the study said. “The WHO has recently concluded that there is no evidence of a correlation between the natural levels of uranium in drinking water and a carcinogenic effect… it emphasised that there is no proof associating uranium in drinking water with a cancer risk.”

The BARC study has been carried out by five scientists — Sanjay K Jha, Aditi Patra, Gopal Verma, Vivekanand Jha and Dinesh Aswal — belonging to BARC’s Health Safety and Environment Group.
According to the researchers, the WHO’s standards of uranium concentration in drinking water — 30 µg/l — were mere guidelines, and not a recommended safety limit.

This was the reason the national standards varied across countries. Finland and Slovakia — two nations with considerable amounts of uranium consumption — have prescribed safety limits of 100 and 350 µg/l respectively; another uranium-rich country, South Africa, has a limit of 70 µg/l. The limits in countries like Canada and Australia that have the largest deposits of uranium among others, however, are 20 and 15 µg/l, respectively. Germany, which does not have uranium, has even lower limits.

According to the BARC study, in the absence of any evidence of adverse health impacts at such small concentrations, considerations like geological (prevalence of uranium) and socio-economic conditions, and population dynamics must also be taken into account while deciding on national standards on uranium contamination.

“In some cases, national regulatory agencies set their own limits for uranium in drinking water, taking into account the local factors and conditions. This decentralised approach acknowledges the need for country-specific standards, recognising the influence of factors such as economic conditions, geological characteristics, and the sensitivity of different population groups,” the study said.

The BARC scientists also pointed out that BIS had not carried out health impact studies before adopting the 30 µg/l limit, unlike several other agencies like the US Environmental Protection Agency (EPA), which did a cost benefit analysis of adopting a stricter standard.

“The USEPA addressed these considerations when establishing the country-specific maximum contamination Level (MCL) value for uranium in drinking water. The EPA’s analysis demonstrated that there is no predictable difference in health effects and kidney toxicity risks between MCLs of 20 µg/l, 30 µg/l and 80 µg/l. The conclusion was that incremental benefits of implementing an MCL of 30 µg/l are significantly greater than those for an MCL of 20 µg/l. Consequently, the EPA established 30 µg/l as the drinking water limit for uranium…,” they said.

The BIS should also have carried out similar impact studies, the BARC scientists said, adding: “It is pertinent to mention that before enforcing a national limit, it is a prerequisite to conduct health-based and epidemiological studies in the country. The existing scientific knowledge about the health effects of uranium, especially at lower concentrations, may have large uncertainties.”

“Since multiple issues influence the limit of uranium in drinking water, it would be prudent to continue with the AERB limit of 60 µg/l,” the study concluded.

The BARC study comes in the midst of increased concerns over uranium concentrations in drinking water, especially after the new BIS standards were notified. In the last five years, the issue of uranium contamination was raised in several questions at the Parliament. The government clarified that the uranium concentration in drinking water was not because of uranium mining activities. “The uranium occurrence is natural, which has been confirmed by investigations,” it said in one of its responses.

In 2021, shortly after the BIS standards were notified, some of these BARC researchers had published findings of a comprehensive exercise to map the uranium content in drinking water sources all over India, that they had been carrying out in collaboration with over 50 institutions across the country for about three years. This exercise had shown that uranium concentrations in surface water was considerably lower than in groundwater sources. About 94 per cent of the 55,554 samples analysed were found to have uranium below the newly notified BIS standards of 30 µg/l, while about 98 per cent were below the AERB standards of 60 µg/l.