Your favorite laundry detergent sends stains and smells packing. But where do those suds go once your clothes are clean?
Most wastewater treatment systems were built to extract just what “we flush down the toilet” before the treated water is released back into the world, said Karl Linden, a professor of environmental engineering at the University of Colorado Boulder who specializes in wastewater treatment technologies.
Unfortunately, that doesn’t include the chemical additives of modern life.
Treatment plants generally rely on a cocktail of microbes to gobble up anything dissolved in water, but certain substances, including surfactants, the chemicals that dislodge the grease and grime from your clothes, can be tough for the standard workhorse bacteria to consume.
Unless your treatment plant has invested in expensive systems beyond what’s required by law, the remnants of your detergent are probably still present when the treated wastewater is released.
“These substances can end up in the sea, river, lakes, etc., where the effluent from wastewater treatment plants ends up,” said Dunia Santiago, a chemical engineer at the University of Las Palmas de Gran Canaria in Spain who studies how detergents move through wastewater systems.
Some of them don’t break down easily in nature and, over time, can build up to levels that are harmful to wildlife, Dr. Santiago said.
Surfactants and artificial fragrances can be toxic to aquatic life or interfere with their reproduction. And, water softeners that help detergents work in hard water can supercharge the growth of algae and microbes, effectively sucking oxygen out of an ecosystem and suffocating creatures that live there.
Here’s what to look for to make your laundry not just clean, but green, too:
First, check the label
It doesn’t help that the detergent aisle is rife with greenwashing. Manufacturers aren’t required to meet objective standards when they put labels like “eco-friendly” or “natural” on their products.
Dr. Santiago said looking for the Environmental Protection Agency Safer Choice emblem could help cut through the noise.
When a product is submitted for to the E.P.A. for certification, “scientists evaluate every single ingredient in the product, no matter the concentration, to assess the potential to cause human and environmental health effects,” said Jennie Romer, deputy assistant administrator for pollution prevention at the agency.
They’re looking for the “safest possible ingredients,” including those that “are safer for fish and aquatic life and break down quickly in the environment,” she said. Safer Choice products must be free of PFAS, the so-called forever chemicals, and phosphates, which are used as water softeners.
Safer Choice takes packaging into consideration, too. If a product’s container isn’t directly reusable, it must contain a certain percentage of recycled material and be recyclable itself.
The environmental option doesn’t have to be a budget buster. “Safer Choice products are available at a variety of price points in many different retail outlets, including dollar stores,” Ms. Romer said.
Pods, powder, liquid or sheets?
It’s not just the ingredients in your detergent that matter. The method of delivery counts, too.
The best way to reduce the environmental effects of your detergent is to not use too much. “A lot of times, people are using way more detergent than they need,” said Joe Zagorski, a toxicologist at Michigan State University’s Center of Research on Ingredient Safety.
Here’s an article from The Wirecutter, the New York Times product review site, on how to make sure your pours are judicious. And here are the pluses and minuses of different products:
Pods: Liquid detergent pods aren’t eligible for the E.P.A. Safer Choice label because of persistent problems with children ingesting them. From an environmental perspective, laundry detergent pods don’t allow you to fine tune the dose of detergent to match the load, which can lead to overuse.
But despite public concern that the pods’ dissolvable coating could create microplastics, Dr. Zagorski said evidence indicated that polyvinyl alcohol, the ingredient that makes a pod’s squishy outer shell, breaks down well during wastewater treatment.
Powder detergents: Powder detergents do allow for precise detergent dosing but don’t perform as well in cold-water washes. That matters, because much of the environmental impact from laundry comes from the energy needed to heat the water, Dr. Zagorski said.
On the positive side, powder detergents frequently come in cardboard containers, which avoids single-use plastic.
Liquid detergents: Liquid detergents work well in water of all temperatures, which helps cut the environmental impact of your loads considerably. They should be as concentrated as possible. There’s no need for extra water in the bottle, which just results in larger packaging and more energy needed to get the product to market.
Sheets: Laundry detergent sheets are sometimes advertised as the plastic-free alternative to pods. In reality, many contain the same ingredient, polyvinyl alcohol, that make up the coating on pods. Wirecutter testers weren’t impressed with the cleaning achieved by the five brands of laundry sheets they tested, noting they left significantly more stains and odors behind compared with their top-choice sustainable liquid detergent. A less powerful cleaning agent can lead to doubling up on the dose.
The bottom line
Taken together, cold-water washing and not using more detergent than you need are probably the most effective ways to support the environment from your laundry room. That makes an unscented, highly concentrated liquid detergent with the E.P.A. Safer Choice label the best option for most households. But you can’t shirk the cold-water washing part.
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