A single cannabis joint has the same effect on the lungs as smoking up to five cigarettes in one go, indicates research published ahead of print in the journal Thorax.

The researchers base their findings on 339 adults up to the age of 70, selected from an ongoing study of respiratory health, and categorised into four different groups.

These comprised those who smoked only cannabis, equivalent to at least one joint a day for five years; those who smoked tobacco only, equivalent to a pack of cigarettes a day for at least a year; those who smoked both; and those who did not smoke either cannabis or tobacco.

Killing cancerous tumors isn't easy, as anyone who has suffered through chemotherapy can attest. But a new study in mice shows that switching off a single malfunctioning gene can halt the limitless division of tumor cells and turn them back to the path of their own planned obsolescence.

The surprising possibility that a cell's own natural mechanism for ensuring its mortality could be used to vanquish tumors opens the door to a new approach to developing drugs to treat cancer patients, according to Dean Felsher, MD, PhD, associate professor of medicine (oncology) and of pathology at the Stanford University School of Medicine.

Even comparatively low levels of air pollution boost the chances of an early death, suggests new research.

The researchers base their findings on long term monitoring of air quality in different electoral wards around Britain during different time periods, and national data on causes of death.

More than 5000 adults aged 30 and above were included in the study.

To assess more closely the impact of pollution on health, they divided the data into four chunks, spanning a total of 16 years each, starting in 1966-70 and ending in 1994-8.

The cause of low birth weights among African-American women has more to do with racism than with race, according to a report by an associate professor of pediatrics at the University of Illinois at Chicago.

Richard David says the quest for a "pre-term birth gene" that is now underway will be of no value in explaining low birth weights.

David and co-author James Collins Jr., professor of pediatrics at Northwestern University, compared birth weights of three groups of women: African American, whites and Africans who had moved to Illinois. Most African-American women are of 70 to 75 percent African descent.

Many scientists assume people have sex for simple and straightforward reasons such as to experience sexual pleasure or to reproduce, but new research at The University of Texas at Austin reveals hundreds of varied and complex motivations that range from the spiritual to the vengeful.

After conducting one of the most comprehensive studies on why people have sex, psychology researchers David Buss and Cindy Meston uncovered 237 motivations, which appear in the August issue of Archives of Sexual Behavior.

Excavations of an underwater Stone Age archaeological settlement dating back 8000 years are taking place at the National Oceanography Centre, Southampton.

Maritime archaeologists from the Hampshire and Wight Trust for Maritime Archaeology (HWTMA) have been working at the site just off the Isle of Wight coast. Divers working at depths of 11 metres have raised sections of the seabed, which have been brought to the NOCS laboratories for excavation.