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A rare head-to-head comparison finds green products aren’t necessarily less toxic

Laundry detergents were among the most toxic tested
September 13, 2022

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Many people assume that household cleaners and personal care products marketed as “green” are less harmful to the environment than conventional brands, and that these products quickly and easily break down to harmless by-products.

But in fact, there’s not much research on this. Corporate secrecy means product recipes don’t have to be disclosed, and “eco-friendly” claims are rarely independently verified.

In fact, some green products are equally or more toxic than their conventional equivalents, a new study shows. And when released into the environment they may become more toxic yet.

Researchers exposed larval grass shrimp and juvenile Daphnia, two crustacean species commonly used in aquatic toxicology experiments, to an array of household products. They focused on aquatic species because household products commonly enter aquatic environments through wastewater and sewage flows, and some of the chemicals commonly found in household products are known to be toxic to aquatic life.

The researchers tested two conventional products and one “green” alternative in each of six categories: laundry detergent, dish detergent, mouthwash, insecticide, dishwasher gel, and all-purpose cleaner. All of the products are widely available to consumers in the United States and were purchased from Charleston, South Carolina grocery stores.

Both green and conventional products are toxic to grass shrimp and Daphnia, the researchers report in the journal Environmental Toxicology and Chemistry.

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In fact, the “green” dishwasher detergent was more toxic to both grass shrimp and Daphnia than both of the conventional options. For some product categories, the picture was more mixed: The green mouthwash was more toxic to grass shrimp than one conventional mouthwash and less toxic than the other, but it was by far the most toxic of the three products in this category to Daphnia, for example. The green dish detergent was again more toxic to grass shrimp than one conventional dish detergent and less toxic than the other, but the least toxic of the three products to Daphnia. The green laundry detergent was more toxic to both animals than one of the conventional options, but about on par with the other. Only the green insecticide was less toxic to these two animals than both conventional products.

“Compared to other product categories, laundry detergents were among the most toxic [products] tested,” the researchers write. This may be because they contained surfactants (a class of chemical that makes up a substantial portion of commercial detergents) that are known to be more toxic than those found in the conventional laundry detergents, they suggest.

The researchers also exposed the grass shrimp to the various products after being broken down by bacteria, and the Daphnia to products that had been degraded by light. Again they found that the “green” products did not reliably break down into non-toxic forms. In some cases biodegradation or photodegradation even made green products more toxic than they had been in the first place.

Take laundry detergent, for example: the green laundry detergent became 1.5-fold more toxic to grass shrimp after biodegradation, but the conventional products became 2.3- and 5.4-fold less toxic. The conventional laundry detergents became 2.4- and 1.4-fold less toxic to Daphnia after photodegradation, but the toxicity of the green laundry detergent did not change.

Overall, none of the green products became less toxic after biodegradation, but nearly half of the conventional products did. Only one third of the green products, but most of the conventional products, became less toxic after photodegradation.

“Green products were not necessarily less toxic before or after degradation treatments,” the researchers conclude. The findings highlight the need for more robust evaluation of products marketed as “green,” in terms of both their toxicity and degradability, the researchers say.

Source: Gray A.D. et al.  “Are green household consumer products less toxic than conventional products? An assessment involving grass shrimp (Palaemon pugio) and Daphnia magna.” Environmental Toxicology and Chemistry 2022.

Image: ©Anthropocene Magazine.

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