A day after a study claimed that 90 per cent of bottled water from leading brands is contaminated by microplastics, Indian bottling companies on Friday contested the findings, saying they enforce strict quality control.

The report, led by Orb Media, a US-based non-profit, revealed widespread contamination with plastic debris including polypropylene, nylon and polyethylene terephthalate (PET) in 93 per cent of the 259 individual bottles across 11 brands sold in nine countries, including Brazil, China, India, Indonesia and the US.

Plastic was identified in 93 per cent of the samples. Particle concentration ranged from zero to more than 10,000 in a single bottle.

The brands tested included Aqua (Danone), Aquafina (PepsiCo), Bisleri (Bisleri International), Dasani (Coca-Cola), Epura (PepsiCo), Evian (Danone), Gerolsteiner (Gerolsteiner Brunnen), Minalba (Grupo Edson Queiroz), Nestlé Pure Life (Nestlé), San Pellegrino (Nestlé) and Wahaha (Hangzhou Wahaha Group).

"Bisleri water undergoes a stringent 10-step purification process. All Bisleri production facilities have their own quality testing labs that ensure that every Bisleri product is made as per guidelines set by the Bureau of Indian Standards (BIS) and WHO (World Health Organisation)," Ramesh Chauhan, Chairman and Managing Director, Bisleri International, said in a statement.

"The safety of our consumers is of paramount importance to us. We are currently investigating this issue," Chauhan added.

The findings suggested that a person who drinks a litre of bottled water a day might be consuming tens of thousands of microplastic particles each year.

On average, plastic particles in the 100 micron (0.10mm) size range -- known as microplastics -- were found at an average rate of 10.4 plastic particles per litre.

Even smaller particles were more common, averaging about 325 per litre.

PepsiCo India also contested the findings.

"Aquafina maintains rigorous quality-control measures, sanitary manufacturing practices, filtration and other food safety mechanisms which yield a reliably safe product for enjoyment anywhere in the world.

"The science of microplastics and microfibres is in its infancy. Microplastic particles are found across our environment, including soil, air and water", PepsiCo India said in a statement given to media outlets on Thursday.

Valued at $147 billion per year, bottled water is the fastest-growing beverage market in the world.

As per the WHO, packaged drinking water is a lifeline for many of the 2.1 billion people worldwide who lack access to safe tap water.

In India, the minimum water requirement for an average adult human who weighs around 64 kg is approximately 6 litres per day, according to WHO.

Besides the potential to cause chronic diseases, contamination of drinking water with pathogenic micro-organisms can cause a number of waterborne diseases.

However, the researchers are not yet sure about the extent and consequences of it on human health, the Orb report said.