Researchers at UCLA suggests that passive smoking does not cause health problems for nonsmokers. Epidemiologists concluded that second hand smoking does not increase the risk for lung cancer and heart disease. An experiment was conducted on more than 35,000 California residents. Those who were part of the study were non-smokers, but their spouses were active smokers. The researchers said they found no significant increase in the death rate from heart disease, lung cancer, or chronic obstructive pulmonary disease, which were linked to smoking. However the study prompted an immediate backlash from critics who called it biased and inaccurate. They challenged the findings, stating the research was partially underwritten by the tobacco industry. They said the study is neither reliable nor independent. This study forms a direct contradiction to reports by World Health Organization, that found a link between secondhand smoke and health problems.