SANTIAGO — Soon it will be that time of year again. Children and the elderly will be wearing surgical masks on the streets. Hospitals will overflow with babies gasping for air. Schools will suspend sports activities.

And everyone will blame everyone else for one of the capital’s longtime ailments: the dark cloud of smog that hovers over its 6 million inhabitants.

Santiago is one of the most polluted cities in Latin America. Trapped in a valley surrounded by the Andes on the east and a coastal mountain range on the west, the capital suffers a thermal inversion during the winter that keeps pollutants from dispersing. Only the winter rains bring relief.

In addition to geography, population growth, poorly regulated transportation systems and manufacturing, and the use of polluting energy sources such as coal and lumber have made smog a life-threatening issue.

When pollution reaches critical levels, public health centers are overwhelmed. A study, commissioned by the government National Environment Commission (Conama) and released in July, found that every year, almost 20,000 people suffer pollution-related health problems in the capital. The report estimates air pollution will cause 720 deaths in Santiago next year.

Now, with rainfall expected to be lower than normal this year, Santiago residents are hoping that an updated version of the government’s 12-year old Prevention and Atmospheric Decontamination Plan (PPDA) for Santiago — which aims to reduce air pollution to adequate standards by next year — will work. Full approval for the plan is expected in several months.

In the past, all sorts of not-so-sensible solutions have been proposed, including blasting a hole through the mountains for ventilation (never done) and a plan to change the location of exhaust pipes on buses (done, but to no avail).

The first comprehensive decontamination plan was created in 1997 after the government declared Santiago saturated (above acceptable levels) with ozone, particle material and carbon monoxide, and near maximum levels for nitrogen dioxide.

The original plan involved some 140 measures to control contamination from transportation (which produces about 40 percent of the city's air pollution), industry (responsible for another 25 percent), commerce, construction, agriculture and households.

Since then, much has improved. In the early 1990s, diesel contained 5,000 parts per million of sulfur, and now it has 50, said Conama director Jorge Lagos. The 1,500 parts per million of sulfur in gasoline were reduced to 30, and in 2001, lead was eliminated from gasoline. Particle matter (PM) fell by more than 50 percent, and the levels of fine particle matter, which is most damaging to people’s health, have dropped 66 percent.

“This was not magic. This was done by the state through the National Petroleum Company, which invested many millions of dollars for this to happen,” said Lagos, whose agency is constantly under fire for not doing enough.

Beginning in the 1980s, whenever pollution has reached high levels, cars have been banned from circulating in the Metropolitan Region, the use of lumber for heating has been prohibited and sports activities are suspended, among other regulations. In the early 1990s, there were about 100 pollution alerts or emergencies a year; last year, there were 20.

Two things were key to these achievements: the introduction of catalytic converters in cars and Santiago’s switch to natural gas. In the mid-1990s, Chile and Argentina signed a deal to provide Chile with a cheap and clean source of fuel. Many vehicles, households and companies adapted their processes and technologies to use natural gas, and the difference in air quality was evident.

Then five years ago, Argentina began closing the pipeline, saying it needed to guarantee domestic supply before selling abroad.

As a result, industries and power plants turned to diesel and fuel oil, once again increasing air pollution. The government, meanwhile, drew up plans for a plant that would import liquefied natural gas and convert it for domestic consumption. The plant is due to begin operating this winter.

Another government plan to decrease pollution had unintended consequences. An overhaul of the public transportation system was so poorly designed that it resulted in more cars on the streets. In addition, the government hasn't demanded that all buses install proper filters. (Lagos, however, hails the fact that from the 14,000 unregulated, contaminating buses in the capital in the late 1980s, there are now 6,500 that use cleaner technologies.)

The updated version of the decontamination plan has stricter standards and enforcement measures and, among other things, encourages bicycle use. It would further restrict car use during high-smog periods.

Lagos said the plan will impose more regulations on firewood use, a large source of contamination in Santiago, and will reduce the level of sulfur in kerosene — widely used in low-income households for heating.

But critics say that focusing just on standards and technology is a mistake.

“Policy-makers aren’t tackling the problem with a global, city perspective,” said Paola Vasconi of the environmental NGO Terram Foundation.

Environmental scientist Marcelo Mena of the Andres Bello University in Santiago believes that much more could be done. “The main obstacle is the lack of political resolve to implement measures that are more than justified by economic assessments,” he said.

Last December, Mena was appointed to the new position of “air manager” — a sort of czar of the decontamination plan. He lacked the powers to be effective in his role, and he resigned in March.

Read more GlobalPost dispatches about pollution:

Waiting to inhale

Bad economy, better lungs?

Chevron vs. Ecuadorean activists

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