The cleaning-product aisles at our local supermarkets are starting to look like Earth Day parades.

Words like "organic," "biodegradable" and "environmentally friendly" are everywhere.

Age-old hippie cleansers such as Dr. Bronner's Magic Soap are available at Trader Joe's, while the shelves at Target — not a chain usually associated with higher planetary consciousness — are brimming with Method's 50 or so different varieties of eco-scrubs in stylish containers.

Despite this blizzard of niche marketing, the question remains: How green is your clean?

Unfortunately, this is not an easy question to answer.

In 1960, the U.S. government passed the Federal Hazardous Substances Labeling Act, freeing companies from disclosing dangerous ingredients in household products unless harmful side effects appear immediately after improper use.

Chlorine bleach must thus be labeled "poisonous" if swallowed, but not as "deadly" when dumped down the drain. Yet deadly it is — and not only to fish.

Mix bleach with many common toilet-bowl cleaners, and chlorine gas is the result. Mix it with ammonia and you'll get chloramines gases. Both are extremely toxic.

When bleach mingles with certain naturally occurring compounds, the results are carcinogenic organochlorines — the same vile offenders found in the infamous, now mostly banned pesticide DDT.

That's only one example. Since World War II, roughly 75,000 chemicals have been introduced into consumer products, but less than 5 percent of them have been tested for health or environmental side effects.

Many of these substances are found inside common cleaners such as countertop disinfectants, bathtub scrubbers and dishwashing liquids. Unfortunately, routine testing of these substances has revealed some un-routine results.

In 1989, the EPA estimated that the fumes produced by common household cleaners were three times more likely to cause cancer than other air pollutants.

A 2007 study published in the American Journal of Respiratory and Critical Care Medicine found that exposure to cleaning products accounts for 15 percent of all asthma cases. Again, these effects are minor compared to the damage such products cause the eco-system.

In response, manufacturers have been slathering their offerings with environmentally conscious labels that often are no more than empty promises.

According to Emily Main, senior editor for the National Geographic Society's Green Guide, "green-washing" is rampant in the household cleaning industry.

"Terms like 'bio-degradable,' 'natural' and 'eco-friendly' are meaningless," Main says. "There is no governing organization to substantiate these claims.

"Lead is natural, but you wouldn't want to be around it," Main adds. "And given enough time, just about everything is biodegradable."

To combat this problem, the Environmental Protection Agency recently introduced its "Design for the Environment," or "DfE" label, which it credits for reducing the use of "chemicals of concern" by 183 million pounds in 2006.

You can find the full list of DfE-certified products here.

According to EPA spokesman Dale Kemery, "DfE compares an ingredient's characteristics to other chemicals in the same class. That is, solvents are compared to other solvents, and wetting agents (surfactants) are compared with other surfactants."

In other words, the DfE logo insures that only the safest ingredients from each class are used — even if the class as a whole may be generally unsafe.

To get around those issues, the Green Guide's Main recommends avoiding products that use vague categories such as "non-ionic surfactants" and "plant-based emulsifiers."

She instead recommends Deirdre Imus' line of Greening the Cleaning products, based at her husband, Don Imus', New Mexico ranch, or Tampa-based Aubrey Organics Earth Aware Household Cleaners, both of which list all their ingredients.

Another stamp to look for is the "Green Seal" label. Used by the independent non-profit Washington, D.C.-based organization of the same name, it holds products to a significantly more rigorous standard than does DfE.

Green Seal certifies that products not only are non-toxic and non-corrosive, but free from carcinogens (as determined by five different major agencies), mutagens (as determined by the United Nations) and truly biodegradable (as certified by the Organization for Economic Co-Operation and Development).

Green Seal's full list of certified products is here.

However, few of the smaller manufacturers' products are certified by Green Seal, which has given its nod to the eco-friendly lines of such consumer giants as S.C. Johnson & Son, makers of Johnson Wax, and Simoniz. And some of the better-known "green" labels aren't on the DfE list, either.

It turns out that the certification process is voluntary for manufacturers, and many of the smaller ones have reservations about it.

"Seventh Generation's product guidelines are either equivalent to or stricter than Green Seal standards, and our work towards continuous environmental improvement is no less rigorous than it would be if we had partnered with DfE," says Christie Heimert, spokeswoman for the Burlington, Vt.-based maker of household and bathroom products.

"We've opted against both, given our concern that a consumer who sees the Green Seal or DfE logo on both ours and a competitive product may incorrectly think the products are equivalent, when, in fact, we believe our own guidelines to be superior," she adds.

Five products on the DfE list are made by San Francisco-based Method, but the company didn't bother with Green Seal.

"We chose to work with the EPA's Design for the Environment program because we feel it represents a comprehensive assessment in terms of environmental quality," says a spokesman. "We are in the process of having the entire home cleaning and hand wash lines recognized [by DfE]."

The venerable Dr. Bronner's line, started by an eccentric Holocaust refugee after World War II, opted instead for a completely different seal of approval. It says it's the first body-care company to be certified as "organic" by the U.S. Department of Agriculture.

The Escondido, Calif.-based company says that means its products are radiation- and pesticide-free, made with sustainable farming practices, and that the ingredients never mingle with non-organic material at any step along the supply chain.

"Now that green is part of the public consciousness, there are just so many programs certifying so many things," says company spokesman Mike Bronner. "We've tried to find the ones that are most stringent."

Despite the certifications, or lack of them, perhaps the most important question about green cleaners is basic: Do they work as well as conventional products?

As Method co-founder Adam Lowry says, "Green, cheap and high-performance are what you want, but there's a rule of thumb that says you can only have two out of three."

In Method's case — which the Green Guide labels as "better" on a scale of "good, better, best" — the company has gone for green and high-performance, with most of its offerings averaging out at 50 cents more expensive than traditional brands.

But what you get for your money doesn't just show up in how clean your counters are, but also how each product gets made.

The manufacture of cleaning products taxes our environment in dozens of ways.

For example, the production of essential oils — used heartily in the industry — can lead to biodiversity-damaging processes such as monocropping, in which the same plant is grown on the same soil year after year, instead of rotating among several species.

To combat such abuses, many companies are aiming for greater transparency in every step in their production chains.

In Method's case, this means consumers can call its hotline for a full ingredient run-down.

Other manufacturers, such as Seventh Generation, have established internal sustainable farming rules (and only work with farmers who follow those rules) and sometimes bring in third-party observers to audit those farmers.

Many companies are going an extra mile to lower the environmental impact of manufacturing. At Method, this means offsetting its carbon production while simultaneously working to lower its freshwater waste. Its Indiana-based manufacturing plant puts no water down the drain.

Containers are another area of scrutiny. Cleaning products generally come in plastic bottles, and where those bottles come from (are they made from new or recycled materials?) and where they go has become another concern.

Legendary green architect-turned-consumer advocate William McDonough has come up with a Cradle-to-Cradle Certification program to ensure materials remain in circulation rather than end up in landfills.

Currently, the only product to have received McDonough's C2C nod is Begley's Best Remover and All Purpose Concentrate, created and marketed by super-green Hollywood actor Ed Begley Jr.

But a number of companies, including Method and Dr. Bronner's, use 100 percent post-consumer recycled plastics in their bottles.

It may be, however, that the greenest cleaning-product manufacturer is you.

Eco-experts say that making your cleaning products at home is the best solution, and recipes can be found all over the Web (try www.care2.com/greenliving/five-basics-for-nontoxic-cleaning.html).

Most are made from simple ingredients such as white vinegar, baking soda and lemon juice — stuff that's a lot friendlier to fish than chlorine bleach.