A recent public health report has stated that cardiovascular and other health problems can crop up even with limited exposure to tobacco.
The US Surgeon General's report, the latest update to its first study in 1964 highlighting tobacco dangers, said that even an occasional cigarette or exposure to secondhand smoke is harmful.
The latest report "substantiates the evidence that there is no safe level of exposure to cigarette smoke," said Surgeon General Regina Benjamin, who serves as the top public health adviser to the White House.
"You don't have to be a heavy smoker or a long-time smoker to get a smoking-related disease or have a heart attack or asthma attack that is triggered by tobacco smoke," said the report.
"Low levels of smoke exposure, including exposures to secondhand tobacco smoke, lead to a rapid and sharp increase in dysfunction and inflammation of the lining of the blood vessels, which are implicated in heart attacks and stroke."
The surgeon general said the report underscores the need to step up efforts to dissuade people from smoking in the United States, where there has been little change in the percentage of users since 2005 after a long period of declines.
"Evidence in this report provides additional understanding that the risk does not increase in a linear fashion with increasing exposure, and even low levels of exposure to tobacco -- such as a few cigarettes per day, occasional smoking, or exposure to secondhand tobacco smoke -- are sufficient to substantially increase risk of cardiac events," the report said.
"Cigarette smoke contains more than 7,000 chemicals and compounds. Hundreds are toxic and more than 70 cause cancer... the chemicals in tobacco smoke reach your lungs quickly every time you inhale. Your blood then carries the toxicants to every organ in your body."
The report added that cigarettes "are designed for addiction" with nicotine and other ingredients and that adolescents "are more sensitive to nicotine" and more easily addicted.