EWG often talks about pollution and health risks in terms of parts per billion or trillion. But what does that mean in simple terms? How can you use this information to live a healthier life?
For this explainer, let’s focus on drinking water, which is often contaminated with toxic chemicals – as highlighted by EWG’s landmark Tap Water Database. When EWG experts discuss toxic chemicals in tap water, they use terms like parts per million, or ppm, parts per billion, or ppb, and parts per trillion, or ppt. These terms describe the amount of a pollutant compared to the overall amount of water.
While amounts like 1 part out of a million, billion or trillion might seem at first glance to be incredibly small and even insignificant, chemicals at these low levels can harm health.
We already know that approved and widely used medications can benefit the body in tiny amounts. Albuterol in the amount of 2.1 ppb can stop an asthma attack. The antidepressant Paxil and the erectile dysfunction drug Cialis are both effective at 30 ppb, and the birth control pill Nuvaring works at just 0.035 ppb.
If these legal, commonly prescribed drugs can cause physiological and psychological changes at such low doses, just imagine the risks of pollutants known to cause a range of health problems if they are present in your tap water at similar or even smaller amounts.
Helpful visualizations
This “parts per” term can quickly get confusing. That’s where visualization comes in. Translating numbers into easily grasped images helps us understand these tiny amounts and their big impacts on our health.
Here are some ways to think about ppb, ppm and ppt.
Millions
Let’s say a pile of 538 Lego bricks – about the amount you’d find in a medium-size Lego set on store shelves – is equivalent to 1 ppm of the chemical barium. It would take 10 million of these regular sets, or 538 million Lego bricks to build the Statue of Liberty.
For scale, 2 ppm would represent just 1,076 bricks in this entire Lego Statue of Liberty – and at 2 ppm, barium can cause health problems. This chemical, found in tap water, is linked to kidney harm, high blood pressure and damage to the heart and blood vessels.
Billions
A single drop of water in an Olympic-size swimming pool is the equivalent of 1 ppb. At first blush, that seems beyond miniscule.
But as little as 5 ppb of trihalomethanes in drinking water can increase the risk of low birth weight.
Trillions
Imagine a map of Texas – 1 ppt is equivalent to 7 square feet in the 7 trillion square feet that make up the state. It takes just a few seconds to walk across this ground.
Yet even at such miniscule levels, the “forever chemicals” known as PFAS can cause serious health risks, including several types of cancer, reproductive problems, low birth weight and more.
Using information wisely
Highlighting the minute scale involved when talking about “parts per” is crucial when we routinely find harmful chemicals in tap water at levels of 1 or less ppm, ppb and ppt.
EWG wants to empower you to live a healthy life in a healthy environment. When more people understand the science of toxic chemicals, we can share our work more easily. And this helps more people make better informed decisions about the products they buy, the food and drink they consume and other ways they can reduce their exposures.
The more people who can visualize EWG’s scientific findings, the more allies we’ll have in our fight to advocate for Americans’ health by pushing for regulatory and legislative action to tackle pollutants at the local, state and federal levels.
