From VOA Learning English, this is the Health & Lifestyle report.

Every day, people come into contact with thousands of chemicals. These chemicals are said to be harmless to human health. In fact, the chemicals are considered so safe that we wash with them. We put them on our bodies and even our faces. Other chemical products are used throughout our homes.

By the time, you walk out your front door you have already been exposed to thousands of chemicals.

On its own, each chemical seems harmless. But in combination with other chemicals, they may become deadly. That is the finding of a two-year study by a high-profile task force of scientists. The task force was told to investigate the cancer-causing possibility of chemical mixtures.

Linda Gulliver was one of 174 scientists on the task force. Their job was to study the cancer-causing potential of 85 chemicals. All 85 are said to be common in the environment.

Ms. Gulliver explains that chemicals have the potential, or ability, to form dangerous mixtures. Even simple minerals can become dangerous when mixed with chemicals found in plastics or beauty products.

"We're talking about everything that could be from basic minerals elements like copper, nickel to pesticides that are used in things like cosmetics and hair sprays and nail polishes and food wrappers."

Ms. Gulliver is also on the medical faculty of Otago University in Dunedin, New Zealand. While the chemicals are safe on their own, she says, the researchers found that many chemical compound cause cancer in human cells.

Working in groups, the scientists explored how different chemical mixtures could lead to cancer. Ms. Gulliver's team looked at the ability of different combinations to support the increase of malignant human cells.

She says the big issue – what she calls ‘the $64 million dollar question' – is, "Which common, every day chemicals do people need to avoid?"

"The $64 million dollar question that everybody wants to ask is, ‘Which ones [chemicals] should we be looking out for?' And the answer to that is, ‘We don't know yet.' "

She says the current way to identify whether chemicals cause cancer is to test them one at a time. This method leads, she adds, to a long list of supposedly "safe" chemicals. She and her team say that approach needs to change.

"We definitely need certain research ... to find out what mixtures of chemicals would be more harmful than others; what groups of chemicals, when together, would produce more harmful effects. And at the moment, that is not known."

An estimated one in five cancers has been linked to chemical exposure. It may turn out that the cancer-causing villain is not a single chemical at all. The villain could be a deadly combination. The increase of risk to cancer could be from exposure to many chemical compounds at the same time, or simultaneously.

The task force published its findings in the journal Carcinogenesis.

And that's the Health & Lifestyle report. I'm Anna Matteo.

VOA's Jessica Berman reported on this story. Anna Matteo adapted it for Learning English. George Grow was the editor.

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expose – v. to cause (someone) to experience something or to be influenced or affected by something : exposure is the noun

potential – n. a chance or possibility that something will happen or exist in the future : potential can also be used as an adjective

task force – n. a group of people who deal with a specific problem

villain – n. someone or something that is blamed for a particular problem or difficulty

simultaneously – adv. happening at the same time: simultaneous is the adjective