When it comes to the environment and sustainability, Wal-Mart has a lot to answer for. The chain sells a lot of plastic and stuff that comes in too much packaging. The stores are full of items that carry a large carbon footprint from being shipped halfway around the world. In many small towns, its big-box stores have forced local shops out of business.

But you have to give the world’s biggest retailer credit for its green initiatives. Wal-Mart has been working to make its stores more energy-efficient, and recently anounced a major solar power initiative. When consumer concern rose about the health risks of BPA, a plastics softener found in baby bottles and formula packaging, Wal-Mart pulled all BPA-tainted products from the shelves. And now the company has announced plans to create a product labelling system that will give customers about the environmental and social impact of every item it sells. The New York Times reports:

Rather than a retailer or a product supplier’s focusing on only a few sustainability goals—lower emissions or water conservation or waste reduction—the index would help them take a broader view of sustainability by scrutinizing and rating all sorts of environmental and social implications.

Did this T-shirt come from a cotton crop that was sprayed with pesticide? Was excessive packaging used to ship these diapers?

Wal-Mart’s plan is perhaps the biggest breakthrough so far in a growing movement for transparency—making it easier for consumers to find out what’s in the products they buy, where they came from and what impact they have on the environment or society. An added benefit is that even shoppers who aren’t necessarily looking for sustainable products will see the labels and stop to think.

In some cases, the transparency push comes from the producer of the product. Sweden is about to become the first country to certify food products as "climate-friendly" if they come from producers that are taking steps to reduce their greenhouse gas emissions.

More often, nonprofit watchdog groups are doing the job. There’s the Environmental Working Group’s Skin Deep, which provides health and safety ratings for more than 44,000 cosmetics and personal care products. There’s GoodGuide, which rates more than 70,000 foods, toys and other consumer products.

As for Earthjustice, we’re going to court in New York this week to argue that manufacturers of household cleaners disclose the toxic chemicals used in their products. The case is far from being decided, but is already having an effect. In response to Earthjustice’s initial request California-based Sunshine Makers, Inc. (manufacturers of Simple Green products), filed a report with the state for the first time. And just three weeks after Earthjustice filed its case, SC Johnson (manufacturer of Windex, Pledge and Glade) announced it would begin disclosing the chemical ingredients in its products through product labels and a website.

What can you do? You can use the resources linked above to learn what’s in some of the products you use. For the others, make it a point to call or write the manufacturer to tell them you have a right to know what you’re putting in your body or using in your home.