Despite loud promises that these gadgets suck out disease-causing bugs from drinking water, most purifiers sold across India do not completely eliminate water-borne viruses like Hepatitis E, says Pune-based National Institute of Virology.
A study by the government-funded body that conducts research on communicable diseases and viruses evaluated eight domestic water purifier brands. It found only two - one equipped with a hollow fibre membrane and the other with a gravity-fed filter - could completely remove the viruses.
The study also found no standards existed for virological evaluation of water purification devices in India and called for well-defined parameters.
The NIV relied on the United States Environment Protection Agency's (USEPA) guide, standard and protocol benchmark for testing microbial purifiers.
The study was conducted by senior deputy director and head of the NIV's hepatitis division, Vidya Arankalle, and scientist Vikram Verma. The Indian Council of Medical Research ( ICMR), ministry of health and family welfare, government of India, extended financial suppo rt to the study conducted by the NIV scientists.
The purifiers that were tested included those using activated carbon filters, ceramic candle filters, sediment filters, iodine resin gravity filters, polyster filters, ultraviolet irradiation, reverse osmosis and hollow fibre membrane filters. These features were either employed singly or in a combination.
The purifiers were evaluated using Hepatitis E vir us (HEV) as a model. The viral log reduction value (LRV) - the capacity to eliminate viruses - was calculated for each purifier.
"The log reduction value (LRV) is the difference in the amount of virus particles between raw water (spiked with HEV) and purified water," said Verma. The US EPA criterion for reduction of viruses is 4.0 log. This means that if there are 10,000 particles in the water that is going to be processed, there should be no viral particles in the water after purification.
"We evaluated one purifier of each brand. The batch-to-batch or unit-to-unit variation was not evaluated. However, even with this limitation, the results indicated that six of the eight purifiers tested did not conform to USEPA standards. The purifiers did not remove the viruses completely," said Arankalle.
"We need a national policy for the evaluation of such purifiers by the regulatory authorities and at the factory level. This will ensure availability of quality domestic water purifiers," she said.
According to Arankalle, viruses remain longer than bacteria in water. "In India, the standard to evaluate the microbial performance of a purifier is for the device to provide bacteria-free water from water in which a fixed amount of Escherichia coli bacteria has been added. However, it is unsafe to rely only on bacteriological standards to assess the virological quality of water. Virological standards should be established immediately," she said.
The Bureau of Indian Standards (BIS), which looks into the standardisation, certification and quality of purifiers, has already appointed a commitee to look into the NIV report.
"The first sectional meeting on water purification equipment was held at the BIS on April 28 this year. The committee discussed the nitty-gritties involved in formulating a regulation regarding the quality of water purifiers. We have also formed sub-committees to look into the bacteriological and microbiological aspects of water purifiers," said Pawan Labhshetwar, who is heading the committee formed by the BIS on water purification equipment.
The meeting was attended by representatives from NIV Pune, NEERI, Chennai, Eureka Forbes, Bangalore and Dehradun, Unilever R&D, Bangalore, Ion Exchange and Whirlpool India, Faridabad. The next meeting will be held in October.
When contacted, K V Thomas, Union minister of state for agriculture, consumer affairs, food and public distribution, told TOI that the upgradation of existing standards was on the anvil. "We need to address the upgradation issue urgently. I will ask the BIS to speed up the process," he said.
While NIV did not reveal to TOI brands of the water purifiers it tested, Hindustan Unilever Ltd insisted that their purifier, Pureit, met all standards.
Vikram Surendran, general manager (water), Hindustan Unilever, said, " Pureit meets the germ removal criteria of the Environmental Protection Agency (EPA), the toughest drinking water regulatory agency in the US. The EPA standard requires a 4.0 log reduction value with respect to virus removal and Pureit meets the same. It is pertinent to clarify that Pureit also removes enteric viruses from water, including the Hepatitis A and Hepatitis E viruses." "The study by NIV in fact identifies Pureit as the device which meets US standards," he said.
Eureka Forbes Limited (EFL), which manufactures water purifier Aquaguard, differed on the methods adopted by the NIV for its study. Marzin R Shroff, CEO, (direct sales) and senior vice-president (marketing), EFL, said, "The Real Time-Polymerase Chain Reaction (RT-PCR) method used in this specific study has been declared unreliable in citations by the global research community for measuring the virus inactivation efficacy of UV-based products, because the method is known to give false positives and is also not approved by global regulatory authorities like the USEPA."
Raman Venkatesh, EFL's senior vice-president (technology), said, "The NIV study does not cite whether the flow rates of products tested are in compliance with the design or rated flow rates, as that will have a great impact on the contact time and dosage of UV-based products, which will impact disinfection efficacy."
Commenting on EFL's objection to the method used in the evaluation, Verma said, "The methodology used in the virological evaluation of water purifiers was recently published in UK-based journal, Tropical Medicine and International Health, after a thorough review. This peer-reviewed journal had been in the public domain for the last one year. If the methodology was unreliable, it would not have found a place in such a prestigious journal."
Verma further said, "We have amplified the complete genome of the virus present in the purified water samples and this is sufficient to prove the infectivity of the virus. We have also taken proper measures to rule out any false positive results with the help of the RT- PCR technique."
Repeated attempts to contact Ion Exchange and Whirlpool India Limited were unsuccessful.
