Nelson Mandela remained in hospital Saturday, a week after he was admitted for treatment for a lung infection, a government official said.

"Mr Mandela is still in hospital, still comfortable and receiving treatment," said presidential spokesman Mac Maharaj.

The United Nations warned Friday that nearly 55 million tonnes of radioactive waste from old Soviet-era uranian mines remain in unsecured sites in northern Tajikistan.

The former Soviet republic, where Stalin's empire once mined uranium to create its first nuclear bomb, is still stuck with about 54.8 million tonnes of unsecured waste from the now mainly abandoned mines, the United Nations Economic Commission for Europe (UNECE) said.

The Obama administration on Friday imposed a new air quality standard that reduces by 20 percent the maximum amount of soot released into the air from smokestacks, diesel trucks and other sources of pollution in its first major regulation since the Nov. 6 election.

Environmental Protection Agency Administrator Lisa Jackson said the new standard will save thousands of lives each year and reduce the burden of illness in communities across the country, as people "benefit from the simple fact of being able to breathe cleaner air."

Brazil is worried that fears over a single case of mad cow disease from more than two years ago could force it to slash its beef prices, after China, Japan and South Africa this week suspended imports.

Agricultural officials here insist there is "no risk whatsoever to public health or to animal hygiene" from the lone case of bovine spongiform encephalopathy (BSE) that was detected in an animal that died in 2010 in the southern state of Parana.

Nearly everywhere around the world, people are living longer and fewer children are dying. But increasingly, people are grappling with the diseases and disabilities of modern life, according to the most expansive global look so far at life expectancy and the biggest health threats.

The last comprehensive study was in 1990 and the top health problem then was the death of children under 5 — more than 10 million each year. Since then, campaigns to vaccinate kids against diseases like polio and measles have reduced the number of children dying to about 7 million.

Nelson Mandela on Friday faced a seventh day in hospital, where he is undergoing treatment for a lung infection.

Officials said the ageing statesman's doctors continued to see progress in his condition, sparking rumors that he could be promptly discharged.

Nearly one in three highway fatalities in the United States last year stemmed from alcohol consumption, the government said Thursday as it launched a holiday campaign against drunk driving.

In 2011, 9,878 people died in alcohol-related road accidents -- 31 percent of all highway fatalities, the Transportation Department said.

Venezuela's President Hugo Chavez experienced "complications," including bleeding, during his cancer surgery, but is showing positive signs of recovery, senior aides said Thursday.

During his treatment, 58-year-old Chavez had suffered "bleeding that required the adoption of corrective measures," Communications Minister Ernesto Villegas said in a television and radio address.

Eli Lilly's experimental Alzheimer's drug has flashed potential to help with mild cases of the disease, but patients and doctors will have to wait a few more years to learn whether regulators will allow the drugmaker to sell it.

Lilly said Wednesday that it will launch another late-stage study of the drug, solanezumab, no later than next year's third quarter. The company's stock slipped in midday trading.

Health officials in the African nation of Gabon say at least 150 people have been sickened by a mosquito-borne illness.

Gabon's Health Minister Marie Josee Ndombi announced Wednesday night in a statement on national television that the patients had been hospitalized with suspected cases of chikungunya fever.