Medical experts on Friday accused a major U.S. breast cancer foundation known for its high-profile "pink ribbon" campaign of overselling pre-emptive mammography and understating the risks.

The Susan G. Komen for the Cure foundation uses misleading statistics in its pro-screening campaigns, two doctors from The Dartmouth Institute for Health Policy and Clinical Practice in New Hampshire wrote in the BMJ medical journal.

Hong Kong choked under the worst smog ever recorded in the city Thursday, with residents warned to stay indoors, away from the blanket of toxic haze, officials said.

Air pollutant readings broke records going back to 1999, except for levels reached when a natural dust storm hit the southern Chinese territory two years ago, environmental protection department spokesman Y.F. Chau said.

Around 22,000 Pakistani children are at risk in Karachi after the World Health Organization suspended polio vaccinations over a spate of bloody shootings, a U.N. official warned Thursday.

WHO, a partner in government efforts to eradicate the disease, suspended activities in part of Pakistan's largest city last month and has not yet been approved to take part in the next campaign due in September.

Researchers presented evidence Wednesday for the existence of cancer stem cells, with three different studies seeking to end a decades-old scientific dispute about how tumors grow.

The discovery should lead to new drugs targeting stem cells that cause tumors to reappear after cancer therapy, the teams argued in three scientific papers published simultaneously in the journals Nature and Science.

Children who suffer or witness physical abuse undergo changes to their brain structure that may predispose them to depression and substance abuse later in life, a study said Wednesday.

The finding holds promise for early detection and pre-emptive counseling already in adolescence -- a crucial phase of physical and emotional development and brain maturation, say researchers in the United States.

The World Food Program has sent supplies to Syria's commercial capital Aleppo to help tackle shortages triggered by escalating clashes between troops and rebels, the U.N. agency said on Wednesday.

The WFP "has sent food assistance for distribution to 28,000 people in Aleppo over the next few days, following reports of shortages of food, gas and electricity following weeks of violence," a statement said.

New York Mayor Michael Bloomberg has a message for new mothers: Breast-feed your baby, if possible.

Starting in September, dozens of city hospitals will ask mothers of newborns to listen to talks about why their breast milk is better than the sample formulas many hospitals offer for free. Then the women can decide for themselves, says the mayor.

Kampala residents have been urged to avoid contact after the deadly Ebola virus hit the city but security guard Joseph Karuba's job is to frisk people and he doesn't have gloves.

"The thing has come back -- it came first time and we beat it, then it came again and we beat it and now it is back," he said, waiting for shoppers outside one of the teeming capital's malls.

It sounds like an unfolding epidemic: A decade ago, virtually no one in the U.S. seemed to have a problem eating gluten in bread and other foods. Now, millions do.

Gluten-free products are flying off grocery shelves, and restaurants are boasting of meals with no gluten. Celebrities on TV talk shows chat about the digestive discomfort they blame on the wheat protein they now shun. Some churches even offer gluten-free Communion wafers.

A new kind of bird flu has been causing deadly pneumonia in baby seals off the northeastern U.S. coast and could pose a risk to humans, according to U.S. research released Tuesday.

The new strain has been named avian H3N8, and is blamed for the deaths of 162 seals along the U.S. coastlines last year, said the study in mBio, a journal of the American Society for Microbiology.