Aly Song / Reuters

A couple wearing a mask and a scarf visits the Bund in front of Pudong Lujiazui financial area on a hazy day in Shanghai on Jan. 16.

Wu Hong / EPA

Waste gas is discharged into the air by an oil refinery plant in Qingdao city, eastern China's Shandong province, on Jan. 16.

Aly Song / Reuters

Travel photos are displayed in a photography service shop at the Bund in front of Pudong Lujiazui financial area on a hazy day in Shanghai on Jan. 16. Chinese media said on Monday the government had to take urgent action to tackle air pollution, which has blanketed parts of the country at dangerous levels in recent days, and one newspaper called for a re-think of a "fixation" on economic growth.

Jianan Yu / Reuters

Children are put on drips as many of them are diagnosed with respiratory diseases at a provincial children's hospital in Hefei, Anhui province on Jan. 16. Days after choking smog blanketed China's capital, the country's premier-designate added his voice to appeals to curb the toxic haze, but he offered few specifics and said there was no quick fix. Particulate matter with a 2.5 micrometer diameter, known as PM2.5, can cause cardiopulmonary disease, lung cancer and acute respiratory infection, according to the Journal of Toxicology and Environmental Health.

Blind growth in China is the cause of the smog that has smothered Chinese cities including Beijing for a week, the government said on Jan. 16 in its first comment on the worsening air quality. Inefficient production methods and the weather were behind the thick, grey air, Vice Prime Minister Li Keqiang was quoted as saying by the state-owned China News Service. 'It warns us once again that we cannot continue the inefficient economic growth model,' he said. Years of rapid growth have vaulted Communist China into second place among the world's largest economies but often at the expense of the environment. The smog has limited visibility, cancelled flights, kept people indoors and sent them to hospitals with breathing, heart and circulation problems.

-- European Pressphoto Agency

Related: Severe Beijing smog prompts unusual transparency

Feng Li / Getty Images

A tourist looks at the Forbidden City as pollution covers the city on Jan. 16 in Beijing.

Previously on PhotoBlog:

• Children line up for flu treatment in Beijing as smog may worsen health issues
• Robot staff at restaurant in China delights customers
• China landslide kills dozens, more remain missing
• Hot colors light up frozen sculptures at the Harbin ice festival
• Taking a full load: Potential students crowd in for entrance exams in China

Petros Giannakouris / AP

Haze of smoke hangs over the city skyline in Athens, early Thursday, Jan. 3, 2013. The cloud is the result of a massive switch to wooden stoves and fireplaces for heating as many households, already hard hit by the economic crisis, can not afford to buy heating oil after the cash-strapped government decided to harmonize taxes on heating oil and diesel fuel, leading to a 40 percent  rise in the price of heating oil.

Follow @NBCNewsPictures

•Sign up for the NBCNews.com Photos Newsletter

Andy Wong / AP

Tan Liang, a resident of Beijing, prepares to take readings on a PM2.5 detector outside his residential compound in Beijing, China, on Dec. 3, 2011.

The Associated Press reports from BEIJING:

Armed with a device that looks like an old transistor radio, some Beijing residents are recording pollution levels and posting them online. It's an act that borders on subversion.

The government keeps secret all data on the fine particles that shroud China's capital in a health-threatening smog most days. But as they grow more prosperous, Chinese are demanding the right to know what the government does not tell them: just how polluted their city is.

"If people know what their air is like, they are more likely to take action," said Wang Qiuxia, a researcher at local environment group Green Beagle, who shows interested residents how to test pollution on a locally made monitoring machine. Continue reading.

Andy Wong / AP

Tan Liang carries a PM2.5 detector towards a garbage-burning facility located near his residential compound in Beijing on Dec. 3, 2011.

Andy Wong / AP

Wang Qiuxia, right, a volunteer from an environmental group, teaches Cheng Jing, left, how to operate the PM2.5 detector in Beijing on Dec. 7, 2011.

Related content:

• China begins to admit 'fog' is really smog
• A smog by any other name
• More world news stories