Why You Should Keep Your Suds in the Tub this Summer

I host a nature challenge for families once a month with the goal of getting kids outside and engaged with nature. With summer in it’s infancy, I’ve been seeing other bloggers post outdoor challenges for parents as well, encouraging families to step outside and explore the natural world together.

However, my excitement quickly turned into dread when one blogger proudly displayed kids playing in baby pools full of soap suds and sliding down slip ‘n slides covered in shaving cream. Don’t get me wrong, I have no doubt these activities are really fun and entertaining for kids and adults alike. But they’re not activities that connect kids to nature.

Introducing household chemicals into nature has negative effects on the environment (effects that you’ll never see and are probably not even aware of).  Given that we deal with pollution and so many other factors that we have little-to-no control over, I think it’s a good idea to be conscious of those decisions that we can control. That is, keeping the suds in the tub and not letting our kids play with soap outside.

What are Detergents Made of?

Surfactants + Builders + Other Ingredients

Surfactants (Surface Active Agents)

Surfactants lower surface tension and emulsify compounds. In other words, they allow compounds like oils, dirt, and grease to mix well with water. By mixing well with water, these compounds are easily removed. Think of washing your clothes using laundry detergent or washing the dishes using dish washing liquid. The dirt and grease come off much more easily with detergent than they would with water alone.


Builders allow the detergent to wash away the grease and dirt (removed by the surfactants) without a trace. They’re what keeps your dishes from being covered in a white film after going through the dish washer. In the past, builders were typically phosphates which have a significant environmental impact (explained below). However, many countries world-wide have banned phosphates along with many states in the US.

Other ingredients include things like fragrances, brighteners, enzymes, etc.


What’s the Difference between Soap and Detergent?

Both are surfactants, but soaps are made from natural ingredients ( plant oils like coconut, vegetable, palm, pine) and detergents are synthetic, man-made derivatives. Detergents contain builders that reduce the white film that’s often left behind in your shower from soap (which does not contain builders).

Is Soap More Environmentally Friendly than Detergent?

Not necessarily. The manufacturing process for soap can use a lot of natural resources (plant oils). Soap also requires more water for rinsing and higher temperatures (more energy) for washing. The surfactants in detergents are designed so that they break down quickly in waste water treatment plants and septic systems. In other words, soaps are not necessarily better than detergents as long as the detergents don’t contain phosphates.

What Do Surfactants Do in the Environment?

Surfactants cause changes in water retention and water transport in the soil making it more difficult for plants to absorb. A scientific review paper (it compared and summarized the results of multiple studies) found that surfactants, even in small amounts alter soil physics, soil chemistry, and soil biology significantly.

So, even if you are using detergents that don’t contain phosphorous, or soaps, the surfactant properties can still have a significant effect if they end up in the environment. This is why it’s essential that all suds go down the drain.


Do surfactants affect the environment if they go down the drain?

A comprehensive review of the scientific literature (over 250 studies!) shows that surfactants have negligible impacts on the environment when disposed of properly – that is, when they go down the drain. Whether your waste water goes through a city water treatment plant or ends up in a septic system, both are designed to break down the surfactants so they have little effect on the environment. Check out the study here. This study looked at the affect of surfactants alone on the environment, not builders like phosphates.

What Do Phosphates Do in the Environment?

Phosphorus is a limited resource in natural environments. Plants need it to grow, but can only grow as fast as the nutrient is available. This is true for other elements as well, like nitrogen. Just like us, plants need the right nutrients in the right amounts to grow and thrive. This is why many household and agricultural fertilizers contain phosphorus.

When people use detergents containing phosphorus, this element ends up in our water. Although some phosphorus is taken-up by waste water treatment plants (there are federal laws that regulate this) some of it ends up in our streams, rivers, and lakes. When aquatic plants like algae have more access to this limited resource, they grow rapidly. This is an example of nutrient pollution.

Nutrient pollution in our surface water lead to eutrophication. Eutrophication is when you have too many plants in the water and it causes the entire ecosystem to get out of balance. Lakes have natural cycles where they

The Process of Eutrophication

extra nutrients in water -> excessive growth of aquatic plants -> plants eventually die -> more bacteria is in the water because it’s breaking down the dead plant material -> decomposition (break down of plant material) requires a lot of oxygen -> there is less oxygen in the water available for fish -> many fish species die – > the species that fed on that fish will have to look other places for food or potentially die themselves.

This is a drastic shift in the ecology of the aquatic system, all by increasing the availability of a single element. This is a great example of why our everyday actions matter! Small things can have a huge impact – for good or for bad!

Should I change my soap and cleaning supplies?

There are many environmentally friendly cleaning supplies on the market that provide great alternatives to cleaners with heavy chemicals or phosphates. They get the job done, their production has a smaller footprint on the environment, and they don’t have the heavy smells you’re accustomed to. In my opinion, I think that changing your cleaning supplies is a good move in the right direction. Not only is it better for the environment, but you’re teaching your kids that sustainability is an everyday choice. There are simple actions you can take daily to decrease your impact on the planet.

Even if you purchase environmentally friendly products, you’ll still want to pour them down the drain so they can be treated.

My family uses a soap company called Pure & Gentle (click here to learn how their products are environmentally friendly). We get our laundry soap, soap bars, body wash, all-purpose household cleaner, and disinfectant spray from this company and have loved using it so far! We’ve been using them for 2 years now. The only thing we didn’t like was the dish-washing detergent. The builders they use were not able to wash away the residue even when used with soft water.


I know this was a lot, but I hope I was able to sum up the science for you. If you have any questions, send them my why.

And remember, Enjoy playing in the water outside this summer, just Keep your suds in the tub!


Thanks for reading,

Dr. Jenny




Christina Cowan-Ellsberry, Scott Belanger, Philip Dorn, Scott Dyer, Drew McAvoy, Hans Sanderson, Donald Versteeg, Darci Ferrer, Kathleen Stanton. Environmental Safety of the Use of Major Surfactant Classes in North America. Critical Reviews in Environmental Science and Technology, 2014; 44 (17): 1893 DOI: 10.1080/10739149.2013.803777

Kuhnt, G. (1993). Behavior and fate of surfactants in soil. Environmental Toxicology and Chemistry. 12(10): 1813-1820.

1 thought on “Why You Should Keep Your Suds in the Tub this Summer

  1. Robert Goodman Reply

    Do you really think the soap or other surfactants dumped on a lawn would persist longer than those that go thru a septic tank under the lawn?

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