Landfill preservation and child mortality.

Is it true that nothing really "biodegrades" in a landfill?

--Laura, via e-mail

Organic substances "biodegrade" when they are broken down by microorganisms into their constituent parts, and in turn recycled by nature. The process can occur aerobically (with the aid of oxygen) or anaerobically (without oxygen). Substances break down much faster under aerobic conditions, as oxygen helps break the molecules apart.

Most landfills are fundamentally anaerobic because they are compacted so tightly that any biodegradation takes place very slowly. "Typically in landfills, there's not much dirt, very little oxygen, and few if any microorganisms," says green consumer advocate Debra Lynn Dadd. She cites a landfill study conducted by University of Arizona researchers that uncovered 50-year-old newspapers that were still readable. Biodegradable materials also might not break down in landfills if they went through an industrial process that left them unrecognizable to the enzymes and microbes that allow biodegradation to occur. Petroleum, for example, biodegrades easily in its original form, but not after it has been turned into plastic.

Some manufacturers say their products are photodegradable, which means that they will biodegrade when exposed to sunlight. But there is little chance that the sun will reach material buried dozens of feet deep in a landfill.

Some landfills are now being designed to promote biodegradation through the injection of water, oxygen or microbes. But these facilities are costly to create and have not caught on. Another recent development involves landfills that have separate sections for compostable materials, such as food scraps and yard waste. As much as 65 percent of the waste currently sent to landfills in North America consists of such "biomass." CONTACT: U.S. Environmental Protection Agency (EPA) Reduce-Reuse-Recycle page; www.epa.gov/ epaoswer/non-hw/muncpl/reduce.htm.

What are the leading causes of child mortality around the world, and what can be done about it?--Susan Hale, Oquawka, IL

A baby girl born in Sub-Saharan Africa faces a 22 percent risk of death by age 15, and more than a third of those who die are babies who don't survive their first month. Infants suffer from low birth weight and poor nutrition. More than 30,000 children under the age of five die each day from preventable causes related to poverty.

Many children suffer from debilitating infections, and analysts say that often casualties could be prevented if just basic sanitation were available. In areas that lack proper sanitation, supplies can easily become contaminated from bacteria in human waste and garbage. According to United Nations statistics, as many as four billion people lack access to safe, clean water.

The Bill and Melinda Gates Foundation has renewed efforts to increase education and distribute supplies such as antibiotics and sterile medical implements. "Some global health problems, like AIDS, have no easy solution, but this isn't one of them," says computer-geek-turned-philanthropist Bill Gates. "The world has an opportunity to stop millions of newborn deaths each year."

Debt and population issues are also causes of this global tragedy. Some poor nations pay more in international loans than on the health and education of their people. Leaders of the world's top industrialized nations last year agreed to cancel $40 billion in debt owed by the world's 18 poorest countries, but this relieves only a sixth of what is owed by African nations.

Populations are also growing well beyond their "carrying capacity." According to Population Action International (PAI), "More than 200 million women in the developing world today wish to delay or end childbearing but do not have access to effective contraceptives. Investments in international family planning assistance are critical."

CONTACT: Make Poverty History Campaign, www.makepovertyhistory.org; Gates Foundation Child Health Program, www.glf.org; Population Action International, www.populationaction.org.