WASHINGTON - A SMOKING ban caused heart attacks to drop by more than 40 per cent in one US city and the decrease lasted three years, federal health experts reported on Wednesday.

Pueblo, Colorado, passed a municipal law making workplaces and public places smoke-free in 2003 and US Centres for Disease Control and Prevention officials tracked hospitalisations for heart attacks afterward.

They found there were 399 hospital admissions for heart attacks in Pueblo in the 18 months before the ban and 237 heart attack hospitalisations in the next year and a half - a decline of 41 per cent.

The effect lasted three years, the team reported in the CDC's weekly report on death and disease.

'We know that exposure to second-hand smoke has immediate harmful effects on people's cardiovascular systems, and that prolonged exposure to it can cause heart disease in nonsmoking adults,' said Dr Janet Collins, director of CDC's National Centre for Chronic Disease Prevention and Health Promotion.

'This study adds to existing evidence that smoke-free policies can dramatically reduce illness and death from heart disease.'

Long-term exposure to secondhand smoke can raise heart disease rates in adult nonsmokers by 25 per cent to 30 per cent, the CDC says.

Secondhand smoke kills an estimated 46,000 Americans every year from heart disease alone. Smoking also causes a variety of cancers, as well as stroke and emphysema or chronic obstructive pulmonary disease. -- REUTERS