研究人员旨在清理南亚的脏窑

Brick, a simple, square block made from baked clay, has been an important building material for thousands of years.

But traditional brick-making methods create pollution that affects health and the climate. Laws governing the industry are weak and not enforced. And there seems to be little motivation for kiln owners to improve on the system.

Low cost labor in brick making

Brickmaking is big business in the South Asian countries of Bangladesh, Pakistan and India. Around 300 billion bricks per year come out of kilns – the large ovens used for hardening the clay.

In India, the industry creates nearly 10 percent of the country's soot. And, it has become a health threat and powerful contributor to climate change.

The brick-making industry depends on low-wage seasonal labor. Whole families of workers move from one kiln to another to find work.

An estimated 23 million workers are employed in at least 100,000 brick kilns operating across the northern state of Punjab, according to a study released in September by Anti-Slavery International.

Women laborer transport bricks on hand carts at a brick kiln factory on the outskirts of Jammu, India, Nov. 26, 2013. Women laborer transport bricks on hand carts at a brick kiln factory on the outskirts of Jammu, India, Nov. 26, 2013.

Nearly all of the workers are given loans from kiln owners before the brickmaking season begins, immediately putting them into debt. The owners withhold their wages during the season, which lasts up to 10 months. They also keep no records, allowing them to pay workers far less than what is due.

Because workers are paid for each piece of brick they make, families put their children to work to increase their output. Many children under the age of 14 work an average of nine hours a day during the hot weather months, according to the study.

Health and climate costs

The industry also uses low cost fuel in low-technology kilns. The fuel includes high-polluting materials such as powdered coal, coal chips, waste oil, agricultural waste, wood, old automobile tires and plastic.

Sachin Kumar is with India's Energy and Resources Institute, also known as TERI. He said that nearly all of the kilns follow one basic design.

"[The] existing technology of brick making in India is [the] Bull's trench kiln, which is highly polluting and energy consuming."

The Bull's trench kiln dates back to the 1800s.

A study by Urban Emissions, an India-based non-profit organization, found that in south Delhi, India, pollution from the kilns might be linked to 15 percent of early deaths caused by pollution in that area.

And in Pakistan, a study by Quaid-i-Azam University found a possible link between brick making and increased cases of anemia and other health disorders.

A better method exists

TERI and others have been pushing the industry to use zigzag kilns. This kiln is named for how air moves back and forth through the bricks.

"So this technology of zigzag kiln is better than the Bull's trench kiln, not only in terms of energy performance but also in terms of environmental emissions."

Kumar says black carbon emissions from the zigzag kiln are about 75 percent lower and it uses 15 to 20 percent less fuel.

That saves owners money, which is a good reason to replace the old kilns. But experts say lack of information, weak laws and poor enforcement make change less likely.

One problem is that authorities generally do not know where many of the polluting kilns are located.

But, Stanford University researchers are working on a way to map them from space.

Stephen Luby is with the Stanford Woods Institute. He saw smoke clouds from kilns while flying over India.

"So then I got thinking, 'Well, wait a minute, if I can do this sitting in a plane, we must be able by remote satellite to detect these as well.'"

Luby's team combined satellite images with heat signals to find the kilns. They even found kilns that a team on the ground did not find during their data collection.

Mapping is just the first step. Redesigned kilns may be cheaper to operate, but replacing the older kilns costs money in advance. And the owners need technical help, too, notes Sachin Kumar.

"Apart from the financial challenge, I think one of the major issues will be availability for the local service providers, because they are the ones who can help him, who can guide him in adopting the zigzag technology."

Across South Asia, there are tens of thousands of Bull's trench kilns to replace.

I'm Alice Bryant.

This story based on two VOA news reports, including a report by Steve Baragona. It also includes information from other news sources. Alice Bryant adapted it for Learning English. Hai Do was the editor.