Passive smoking is being blamed for an increased risk of death, heart disease and the slower healing of wounds.
Passive smoking under scrutiny
Research published in the British Medical Journal online found a 15% higher risk of death among non-smokers who live with a smoker.
Another study showed the number of heart attack admissions in Helena, US, fell by 40% during a smoking ban.
And research published in BMC Cell Biology suggested passive smoking damages cells needed to heal wounds.
Deborah Arnott, director of anti-smoking campaigners ASH, described the research as "three vital pieces of evidence on the need for tough action
against second-hand smoke".
She added: "The case for a new law to end smoking in the workplace and in enclosed public places is now overwhelming."
The first study was based on the 1981 and 1996 censuses in New Zealand among those aged 45 to 74.
Researchers from the Wellington School of Medicine and Health Sciences said even after age, ethnicity and social background were taken into account, the 15% increased risk of mortality for passive smokers remained.
They said: "The results from this study add to the weight of evidence of harm caused by passive smoking and support steps to reduce exposure to other people's smoke - in the home and in other settings."
The Helena ban on smoking in public places and workplaces was imposed between June and November 2002 before a legal decision overturned it.
Hospital admissions for heart attack during the ban and for the same months from 1998 to 2003 were looked at by researchers from the University of California.
They found admissions fell from an average of 40 during the same months before the ban to 24 during the ban.
The researchers said their findings suggest that "smoke-free laws not only protect people from the long-term dangers of second-hand smoke but also that they may be associated with a rapid decrease in heart attacks".
The final study, into wound healing, found fibroblast cells became more adhesive because exposure to smoke altered their chemical make-up.
As well as reducing the speed of healing, this would account for abnormal scarring of wounds in passive smokers, as the cells remain concentrated at the edge of the wound, preventing it from closing properly, the researchers said.
Experiments are now being carried out on mice. Early results suggest those exposed to smoke for six months have wounds which heal more slowly.
The researchers said: "It is our hope that this work will lead eventually to the realisation that second-hand smoke exposure can be very damaging."
Dr Stuart Enoch at the Wound Healing Research Unit at the University of Wales College of Medicine, said the research was interesting but had to be treated with caution.
He said: "It is very difficult to do a trial on passive smoking on patients because exposure is very variable. we have to be very careful about extrapolating from this."
Pro-smoking lobby Forest argues that the "jury is still out" on the effects of passive smoking.
Simon Clark, director of the organisation, said: "If passive smoking is such a killer, they should produce some case studies of people who have died from it.
"Instead, people get their calculators out and rely on statistsics."
He said the evidence remained "inconclusive".
Dr Vivienne Nathanson, head of science and ethics at the British Medical Association, said the three pieces of research confirmed that passive smoking was "a
very real risk".
She repeated a call for a ban on smoking in public places.