Smoking has devastating health consequences, even if you smoke just a pack per week. An October 2005 study report published in "Tobacco Control" found that the relationship between smoking and adverse health consequences occurs even among people who smoke 1 to 4 cigarettes per day. The surgeon general has confirmed these findings, concluding there is no safe level of exposure to tobacco smoke -- including secondhand exposure.
Coronary Heart Disease
Even at low levels of exposure, cigarette smoking increases the risk for cardiovascular disease. The surgeon general concluded in 2006 and again in 2010 that light smoking and secondhand exposure have immediate harmful effects on the body. This harm comes in the form of damage to the blood vessels and sets off chronic inflammation that fuels atherosclerosis, the most common cause of coronary heart disease. Smoking 1 to 4 cigarettes more than doubles the risk of dying from coronary heart disease compared to nonsmokers, according to the authors of the 2005 "Tobacco Control" study report.
Chronic Obstructive Pulmonary Disease
The authors of an October 2012 study report published in the journal "Chest" found that people exposed to secondhand smoke have more than double the risk for chronic obstructive pulmonary disease, or COPD, compared to nonsmokers not exposed to cigarette smoke at home or work. Given that even exposure to secondhand smoke significantly increases the risk for COPD, it is reasonable to conclude that light smoking has a similar or greater effect. Findings from a study published in February 2013 in "Respiratory Research" confirm this notion. The researchers report that past or current light smoking significantly increases the risk for developing chronic bronchitis, a form of COPD.
The researchers who conducted the study published in "Tobacco Control" in October 2005 reported a substantially increased risk of lung cancer among light smokers. Women in the study who smoked 1 to 4 cigarettes daily were 5 times more likely to develop lung cancer and men were 3 times more likely, compared to nonsmokers. Light smoking for a longer duration may be more harmful than heavy smoking for a shorter duration, according to the authors of a March 2006 study report published in "Cancer Epidemiology, Biomarkers & Prevention." A separate group of researchers reported in the December 2006 issue of the same journal that even light smokers and people who have reduced the number of cigarettes smoked daily experience high levels of exposure to cancer-causing chemicals from tobacco smoke.
According to a 2006 surgeon general's report, exposure to secondhand smoke during pregnancy is a contributing factor to sudden infant death syndrome and low birth weight. The report also found that exposure to secondhand smoke during pregnancy may increase the risk for preterm delivery and childhood diseases, including cancer, leukemia, lymphoma and brain tumors. It is reasonable to conclude that light smoking has at least similar risks.
Light Smoking Shortens Your Life
The October 2005 "Tobacco Control" study found that smoking just 1 to 4 cigarettes per day significantly increases the risk of death. The 2006 surgeon general's report concluded that exposure to secondhand smoke leads to an earlier death. In the 2014 report, the surgeon general estimated that smokers' lives are shortened by a decade. If you quit smoking by age 40, the surgeon general estimates you can reduce that loss of years by 90 percent. Quitting by age 60 is estimated to reduce years of life lost by 40 percent.