Endless lines of slow-moving cars emerge like apparitions and then disappear again into the gloom of the thick smog that has shrouded Beijing this week and reduced its skyline to blurry gray shapes.

With more than 13 million cars sold in China last year, motor vehicles have emerged as the chief culprit for the throat-choking air pollution in big cities especially Beijing, which has suffered even more than usual these past few days.

As the Chinese middle-class expanded dramatically over the last 20 years, cars became the new symbol of prosperity. With the economy continuing to grow, the love affair with cars will only bloom more, and is already posing a challenge for dealing with the hazardous air pollution in urban China with widespread impact on health, productivity and quality of life.

The attachment for automobiles has turned into a vicious cycle.

“To be honest, the more the air is polluted, the more I prefer to drive, as I don’t like taking a crowded bus or walking outside in such bad air,” said subway train driver Gao Fei.

Twenty years ago, bikes, not cars, owned the streets. Today, “buying a car is like buying a bicycle,” said Gao as he drove his black Buick Regal sedan in west Beijing.

“It hasn’t been long since Chinese people owned their own cars. So for them a car is still something quite fresh and so they prefer to drive after so many years of riding bicycles,” he said. “They still would prefer to enjoy the traffic jam rather than suffer on the crowded bus.”

In the 1990s, the few vehicles on the roads belonged to the government or state companies. Private car ownership took off exponentially only in the last decade.

The government has promoted car buying as a way of keeping the economy growing with banks offering attractive car loans. These policies, and the traditional Chinese habit of saving, have put cars like Gao’s Buick Regal (price tag 180,000 yuan, or $29,000) within the reach of many Chinese even though the average annual salary in Beijing is 56,000 yuan ($8,900).

The result has been increased vehicle emissions.

While burning of coal for power plants is a major source of air pollution across China, vehicle emissions are the single biggest source of PM2.5 — a secondary pollutant that forms in the air and is tiny enough to enter deep into the lungs — in Beijing, according to the capital’s former vice mayor, Hong Feng.

He says vehicles account for 22 percent of PM2.5 in the capital, followed by 17 percent from coal burning and 16 percent from construction site dust. In recent days, air quality went off the index in Beijing as the capital turned into a white landscape with buildings eaten up by murk.

Zhang Quan, a former soldier, said the smog was the worst and longest-lasting he had seen in his life.

“When I was young, our geography teacher taught us how to recognize the galaxy and I could find it at night, but I guess kids nowadays can’t do that anymore,” said Zhang, 52.

China’s increasingly informed and vocal citizens have successfully pushed the government to be more transparent about how bad the air is, taking to the country’s lively social media to call for better information and even testing the air themselves. Hourly air quality updates are now available online for more than 70 cities, and two particularly bad bouts of hazardous air this month received unprecedented coverage in the state media.