Neetu Singh worries about cancer. So the 44-year-old Lucknow resident follows a set of strict rules. She doesn't use plastic ware in microwave ovens. And she stays away from synthetic shampoos and cosmetics.

Heating food in a plastic vessel, the researcher at the Lucknow-based King George's Medical University (KGMU) stresses, leads to 55 per cent more harmful chemicals leaching into food.

"Add to that pesticide residues in vegetables and cereals and you have a deadly concoction," says the cancer biologist at KGMU's Advanced Molecular Science Research Centre.

Singh knows what she is talking about. She has been part of an international effort to probe whether daily-use chemicals - which are considered safe in tiny doses - are nudging us towards cancer.

The international team comprising 174 cancer researchers and physicians from 28 countries scoured existing scientific literature on 85 commonly-used chemicals. To their shock, they found that about 50 chemicals can actually aid cancer growth when combined with one or more chemicals.

Fears about cancer caused by products or food earlier seen as harmless are being voiced across the world. Last month, the World Health Organization put processed meats alongside cigarettes and asbestos as known causes of cancer. Red meat may be carcinogenic if eaten over time, the WHO's International Agency for Research on Cancer said.

The role of chemicals has always been a cause for concern. For nearly a century, chemicals have been part and parcel of modern life. They are present in processed and packaged food products, in cosmetic and personal care products, in plastics and in fruits and vegetables.

Through the day, a person comes in contact with a large number of chemicals from multiple sources. Scientists now worry that tiny doses of these "safe" chemical cocktails may be pushing people towards cancer in the long run.

"In our lifetime, we humans are exposed to as many as 88,000 man-made chemicals. They are present in the food we eat, water we drink and the air we breathe," says Singh, who did her doctorate from the Central Drug Research Institute, Lucknow.

A great many common products - from shampoos, sunscreens and toothpastes to plastic water bottles - carry chemicals. Some of these chemicals are used as preservatives in personal care products, hand sanitisers and antibacterial soaps. Others are added to plastics and other products to make them durable and flexible. Then there are agrochemicals which are used to protect crops from weeds and pests and insecticides sprayed to control insects such as mosquitoes.

Individually, most of these chemicals at low doses are relatively harmless. But if you are using a chemical shampoo and sunscreen, washing hands with an anti-bacterial soap, using a sanitiser and drinking water from a plastic bottle on a regular basis, even low-dose exposures to the mix of chemicals can trigger cancer in the long term.

"Research backs up the idea that chemicals not considered harmful by themselves are combining and accumulating in our bodies to trigger cancer," says Hemad Yasaei, a cancer biologist at Brunel University in the UK.

The research that Yasaei refers to was the outcome of an effort initiated by a Canadian non government organisation called Getting To Know Cancer. The NGO decided to put together an experienced team of cancer researchers and physicians. Under a project called Halifax (named after the Canadian city where the teams met in 2013), the scientists were asked to examine what effect - big or small - these chemicals have on cancer development and its progression.

For this, the scientists were bunched into different groups that studied the effect that these chemicals had on 10 different cellular mechanisms that were earlier found to aid cancer development.

These mechanisms - which are actually the hallmarks of cancer - include genetic instability, tumour-promoting inflammation, avoiding destruction by immune cells and inducing new blood flow (which would help newly formed tumour cells).

The scientists, among them many of Indian origin, recently published their results in a series of papers in the research journal Carcinogenesis.

These 50 everyday chemicals included bisphenol A (used in manufacturing plastics), triclosan (often found in hand sanitisers and anti-bacterial soaps) and atrazine (a commonly used herbicide). Each of these chemicals affects different processes that could lead to cancer.

For instance, bisphenol A disrupts cell division, which happens in the body normally, as well as cell-to-cell communication. Atrazine encourages inflammation. Hence, it's reasonable to assume that consuming a mixture of these chemicals puts a person at a greater risk.

Though comprehensive in nature, this is not an isolated study. About two weeks ago, Dale Leitman, an adjunct professor of nutritional science and toxicology at the University of California, Berkeley, and his colleagues found that parabens - a group of chemical preservatives commonly used in shampoos and body lotions - could stimulate the growth of breast cancer cells at doses much lower than previously thought.

The UCB researchers carried out the study on breast cancer cells bred in a laboratory and they still need to understand whether the chemicals will behave in the same manner in the human body.

Lab and animal studies in the past too had established parabens' ability to mimic the activity of the naturally-occurring sex hormone, oestrogen. These chemicals bind to those cells in the body to which oestrogen normally binds. While this is fine in normal cells which have a mechanism to stave off the harmful impact, in tumour cells it would lead to breast cancer cells multiplying.

There's worse. Leitman's team reported in the journal, Environmental Health Perspectives, on October 27 that when scientists mixed parabens with an additional compound called heregulin - a protein normally found in normal breast cells - parabens were 100 times more powerful at stimulating cancer cell growth than without heregulin.

Explaining the role of chemicals, the scientists point out that cancer is caused mainly by the imbalance between cells dying and being born. In a healthy body, the rate of cell growth is equal to the rate of cell death.

"Cancers can occur because of excessive cell growth and not enough cell death," says Paramita Ghosh, a Calcutta-born associate professor at the University of California, Davis (UCD). Ghosh was a part of the Halifax project and studied the effects of environmental chemicals on cell death.

The team of which Ghosh was a member was led by Dr Hyun Ho Park of the School of Biotechnology, Yeungnam University, South Korea. Their study described different molecular mechanisms by which cells can die and explored how exposure to low dose chemicals in the environment prevents cancer cells from dying. In such cases, even cancer drugs do not help.

"Since the individual cancer cells do not die, the tumour keeps on growing," explains Ghosh, who is engaged in research in prostate cancer development and progression at UCD's Comprehensive Cancer Center.

"The most significant conclusion that emerged from the review of the literature is that it is not any single compound but a combination of compounds that results in carcinogenesis," Ghosh adds.

Indian scientists are already picking up signs of excessive presence of these harmful chemicals in Indians. For instance, Kurunthachalam Kannan, professor of public health at the State University of New York, and his Indian collaborators found harmful chemicals such as bisphenol A, parabens, triclosan and oxybenzophenons in the urine of 70 per cent of children they tested in India.

These chemicals, he explains, disrupt hormonal production in the body. "These chemicals can accumulate in the blood and liver," says Kannan, whose paper is scheduled to appear in the December 2015 issue of Environmental Research.

Is it time to press the panic button? Dr Mohandas K. Mallath, a cancer specialist at the Tata Medical Centre in Calcutta, doesn't think the findings are clinically significant. Most chemicals cannot be banned because they are an essential part of modern living.

However, there are other ways of handling cancer. Tobacco, for instance, is a far more dangerous cancer-causing product than these chemicals.

"Almost 90 per cent of cancers today are preventable. Banning tobacco alone can help reduce cancer incidence by 50-60 per cent," Dr Mallath says.

Dr Abbas Ali Mahdi, who heads the biochemistry department at KGMU, holds that the "the everyday chemical soup that we absorb into our bodies just by living in the modern world" hits hard at the liver and the kidneys.

"All these toxins are dealt with in the liver," he says. Perhaps that is why there is an increase in the incidence of non-alcoholic fatty liver disease, which sometimes also leads to liver cancer," Dr Mahdi points out.

Meanwhile, the Halifax project has moved on, and scientists are looking for ways of treating cancers which are more effective, less toxic and capable of tackling drug resistance and relapse of cancers. There is, perhaps, a sliver of light at the end of the chemical-laden tunnel.