In the United States, many people think of drunk driving when they hear the term "breathalyzer."

If you are suspected of driving under the influence of alcohol, police will most likely ask you to breathe into a breathalyzer. This device identifies how much alcohol is in your blood by measuring the amount of alcohol in your breath.

Now, researchers are using the same technology to test for something else: cancer.

This breathalyzer, created by Owlstone Medical, can identify and measure chemicals in a person's breath. And it finds these chemicals at very low levels, usually parts per billion.

British researchers have asked 1,500 people to take part in tests of the device. Each person will wear a special mask and breathe normally for 10 minutes. The mask is equipped with collection tubes. These tubes capture the chemicals in the person's breath.

The lead investigator is Rebecca Fitzgerald of Cambridge University in England. She says the Owlstone breathalyzer is a simple device.

"These tubes -- simple though they look -- this is one of the things that's made a real difference in this technology looking so promising, because for the first time the chemicals that are breathed out in the breath, can be collected in these tubes and immediately stabilized. So as you keep breathing you're capturing more and more of those chemicals and you're building up a profile of the chemicals in your body that are being exhaled on the breath."

The tubes are then sent to Owlstone's laboratory. There, researchers examined the volatile organic compounds in the breath. Those VOCs, as they are known, are produced by the body's normal chemical processes.

However, changes in chemical activity can produce particular markings. And those markings can be biomarkers, providing evidence of disease.

Some biomarkers may show evidence of cancer in its earliest stages. Cancer develops in stages. The earlier cancer is identified, the greater the chance of survival.

One of Owlstone's founders is Billy Boyle. He says cancer often appears or as he says, "presents" itself after it has spread.

"The challenge is most people present when it's very late stage, and it's about managing symptoms as opposed to curing them. So the key thing that you can do is detect the disease early. And that's what we think the breathalyzer technology allows for...picking it up at that earliest stage when it's treatable."

The testing of the Owlstone breathalyzer is currently limited to patients with suspected esophageal and stomach cancers.

Esophageal cancer is a leading cause of cancer deaths around the world. Most cases are reported in developing countries.

Esophageal cancer in its early stages usually has no signs. However, the chemical markers of the disease are present even in the earliest stage.

Over the two-year trial, researchers will extend testing of the breathalyzer to include patients with other cancers.

I'm Anna Matteo.

Faith Lapidus reported this story for VOA News. Anna Matteo adapted it for Learning English. George Grow was the editor.

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biomarker – n. biological evidence of a process, event, or condition

allow – v. to permit (someone) to have or do something; to let (someone) go or come in or out

symptom – n. a change in the body or mind which shows that a disease is present

mask – n. a device covering part of the face, including the mouth

stabilize – v. to make or become unlikely to change suddenly or greatly

profile – n. records showing information about something

exhale – v. to breathe out.