For the last three weeks, residents of Beijing have been breathing thick, soupy air so choked with pollutants that it has registered far off the scale of acceptable levels.

Yet places like Beijing or New Delhi, India, which has also had extremely unhealthy air quality levels, are far from the only cities to be plagued. Air pollution affects practically everyone on the planet and causes more than 6 million premature deaths every year, according to the World Health Organization. Yet, this insidious and long-standing issue really only generates headlines when it hits extreme levels.

ABC News correspondent Gloria Riviera reports that levels in Beijing averaged 300 on the Air Quality Index (AQI), a whopping 280 points over what WHO says is good, clean air. Optimal AQI is just 20.

Explosive economic growth in China means factories are going full tilt 24/7 and millions of people are able to own cars for the first time. China has minimal environmental standards in place. The new pollution over Beijing provoked the Chinese government, for the first time, to issue an emergency warning about the air. People were told to stay indoors, some factories were shut down, and about a third of government cars were ordered off the roads.

“There are many places around the world where air pollution represents a major public health issue,” said Dr. Maria Neira, director of the Department of Public Health and Environment at WHO, in an interview with Christiane Amanpour. “But we don’t have a ranking because many of the cities around the world, even those expected to have high levels of air pollution, don’t have a regular or routine system to measure air quality.”

WHO’s recommendation is to initiate monitoring, particularly of particulate matter, which is one of the best indicators of pollution for health impacts.

The health hazards of air pollution vary, often based on how long and to how much a person is exposed. Acute effects include pneumonia, while in the long term it can lead to emphysema, lung cancer and cardiovascular diseases. Children, the elderly and those with already comprised immune systems are particularly susceptible.

The types of pollution vary as well. WHO makes a distinction between indoor and outdoor air pollution.

“Indoor air pollution mostly affects developing countries,” said Neira. “Half the world still relies on solid fuels like wood for heating and cooking. It’s inefficient and damaging to health and causes 3.5 million premature deaths every year.”

By contrast, outdoor air pollution affects emerging and developed countries and prematurely kills 3.3 million people every year, because of pollution from industrial uses and manufacturing, and energy inefficiency.

Neira noted that worldwide there is major interest and awareness of the problem of air pollution and the knowledge that links air pollution to health consequences. And though there have been improvements in policy recommendations, there has been a lag in results and improvements in public health.

“We need to take very dramatic decisions, especially in the big cities, where they are planning now for urban development,” said Neira. “There are certainly very good ways to have industrial development and protect the health of the environment. When you start to plan a city, you must include health criteria.”

Some of her recommendations include promoting more sustainable public transportation and clean technologies that will filter pollution from industrial production.

“The moment we take interventions, even very quickly, you will see an impact on the health of the people,” said Neira. “Good results can be obtained with rapid interventions that are now available.”

And there is an additional benefit to reducing air pollution. Many of the factors contributing to global warming, such as black carbon, are also major air pollutants.

“If you take interventions in climate change, you will have a benefit in air pollution and vice versa,” said Neira.