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The evidence is stronger than ever that pollution from industry, traffic and power generation causes strokes and heart attacks, and people should avoid breathing in smog, according to a report the American Heart Association released last week.

Among those already suffering from heart conditions, long-term exposure to air pollution can bring about a deterioration in their conditions or even death, the AHA found.

The report calls for an awareness campaign to be launched to inform heart-disease patients - and other vulnerable populations such as the elderly and diabetics - of the dangers posed by air pollution.

The report was conducted by a team of experts from various fields, including three who will arrive in Israel over the next few months for a conference organized by the Environment and Health Fund, a non-profit advocacy group. The conference comes ahead of clean-air legislation slated to be enacted in Israel next year.

The report's authors note that studies conducted over the past few years have confirmed that small contaminant particles (as small as 2.5 microns across ) can penetrate deeply into the respiratory system and even lead to death among heart patients after exposure of just a few hours or days.

"Particulate matter appears to directly increase risk by triggering events in susceptible individuals within hours to days of an increased level of exposure, even among those who otherwise may have been healthy for years," said Dr. Robert Brook of the University of Michigan in Ann Arbor, who headed the group writing the report.

'Risk factors must be controlled

"The foremost message for these high-risk groups remains that they should work to control their modifiable traditional risk factors - blood pressure, cholesterol, diabetes, smoking," Brook said.

The report stated that fine particulates could work in several ways, including by causing inflammation. "It's possible that certain very small particles, or chemicals that travel with them, may reach the circulation and cause direct harm," Brook said.

"These responses can increase blood clotting and thrombosis, impair vascular function and blood flow, elevate blood pressure, and disrupt proper cardiac electrical activity which may ultimately provoke heart attacks, strokes, or even death," he said.

A review of six year's worth of medical research also showed strong evidence that pollution can help clog arteries, and a "small yet consistent" association between short-term exposure to air pollution and premature death.

The group recommends that the elderly or anyone with heart disease, high blood pressure, high cholesterol, or diabetes should pay attention to air pollution and air quality index warnings.

"People can limit their exposure as much as possible by decreasing their time outside when particle levels are high and reducing time spent in traffic - a common source of exposure in today's world," Brook said.