Dear Umbra, I've scrounged some old wooden shipping pallets for garden projects -- compost piles and raised planting boxes. They appear to be untreated wood, but I'm feeling paranoid. Is there any way to know? Do companies that make pallets routinely spray them with any preservatives? Thanks,Jim Dearest Jim, Great nations consider your humble garden pallets to be of vital economic importance. As world trade expands, the global market often rests, literally, on shipping pallets. Goods visit many shores before reaching the stores, and tiny little hobos -- wood-boring insects such as the pine borer and the Asian longhorn beetle, …

Dear Umbra, What sort of grill (charcoal or gas) is the fairest of them all -- speaking from an environmentalist's viewpoint, of course! R. Widiss Dearest R., Gas. I gather that lively debate exists in the barbecue set over which yields better flavor: the briquettes, with their flavorful smoke and irregular heat, or boring old gas, which cooks evenly and imparts fewer smoky (aka burnt) flavors to the object de grill. Not much debate over the environmental results, though: Burning charcoal gives off more nasty particulates and chemicals. And if you're carnivorous, you're doubly culpable: cooking beef can be worse …

Kindergarten is starting next week, and the worn-out old sneakers from last spring are pinching my daughter's toes. No shoes fit at our favorite used-clothing store, and no neighbors have the right pair of outgrown sneakers to offer this season. There is no avoiding it. One morning, as early as I can manage, I load Jenna and her little sister into the car. We are going shoe shopping. I thought we were getting an early start, but this is "Back To School Specials Week" and the store is crowded. We stand before the display rack, immobilized at first by the …

After endless days of discussions, noisy protests, and a near-walkout by delegates from the European Union, negotiators at the World Summit on Sustainable Development reached agreement yesterday on a plan to address poverty and environmental degradation. The plan is expected to be ratified by the more than 100 world leaders assembled for the summit in Johannesburg, South Africa. It outlines initiatives on everything from removing trade barriers that harm the economies of developing nations to providing basic sanitation to poor people, to restoring marine fish stocks. Most environmentalists and some delegates were disappointed with the plan -- especially with provisions …

Can capitalism and environmentalism go hand in hand? A new breed of financiers thinks so, and is making money by treating air pollution as a commodity. Here's how it works: Companies are required to cut their emissions to a certain level; if they do better than those targets, they can sell pollution credits to other companies that are still exceeding allowable emissions levels. The emissions targets are set by a variety of agencies, from state governments to the U.S. EPA. Most of the trading, however, is spurred by the possibility of international caps on CO2 emissions under the terms of …

And speaking of the World Summit on Sustainable Development -- in preparation for the commencement of the event, the New York Times devoted today's Science section to coverage of international environmental issues. From the impact of human behavior on the global ecosystem to the economics of renewable energy; from reassessing international population growth to our love-hate relationship with nature (dolphins, yes; scorpions, yikes!); from the environmental argument in favor of logging to the nature of disease in a changing world, this special section on "Managing Planet Earth" covers a wide range of issues.

Dear Umbra, Longtime reader; first-time writer. Love the column. My partner and I recently bought a small station wagon to replace our 4WD pick-up and '83 sedan. After some debate, we chose a turbo-diesel engine that boasts about 45 miles per gallon instead of a gas engine, which gets about 30 MPG. Our thinking led us to choose the higher fuel efficiency and lower CO2 emissions of the diesel engine, although the gas engine produces fewer particulate emissions, sulfur, and other nasties. Would you please comment on our decision, and also help us understand the other pollution and energy costs …

Dear Umbra, In 1981, I bought my first car, a Honda Civic. It was a great car, and despite what certain congressional leaders say about car size and safety, an excellent vehicle for handling winter snow and ice in mountain driving in Steamboat Springs, Colo. The problem is that now, living in Pennsylvania, my husband and I and our three children are looking for a car that will be able to carry the five of us for the next 10 years without destroying the planet. We had to buy a used van when the kids were younger because, try as …

Dear Umbra, Is it more efficient to drive down the highway with my windows down or the air conditioner on? I know the air conditioner decreases gas mileage, but I bet having my windows down at 75 miles per hour produces pretty good drag. Thanks,Sara Dearest Sara, This is July's Question of the Month for Grist readers, apparently. I received a passel of virtually identical queries with minute variations. ("How much drag do you get from a drooling dog?", etc.) Car air conditioning has obvious benefits, especially if you have a long commute in a sprawling all-road-all-the-time Southern city. With …