Human Health Risk Assessment—What it’s all about

Three images arranged horizontally: grade school students in classroom; girl with arms raised; bicyclists at sunrise

By Kacee Deener 

Scientists need to be able to describe—in a way everyone can understand—what we do and why it’s important.  That’s one reason I’ve decided that I need to strengthen my “elevator speech” about what I do (human health risk assessment).  I will be writing blog posts over the next several weeks trying to explain human health risk assessment in plain language.

For this first post, I’ll introduce the concept of risk and explain why human health risk assessment is important.

Risk is something we all understand.  In fact, we all assess risk every day.  What is the risk of swimming in the ocean on a clear day?  Does the risk change if there are jellyfish? How about an approaching storm?  A shark swimming nearby?  We all understand these types of risk calculations at a very intuitive level.

Human health risk assessment isn’t so different.  It’s a process of characterizing the nature of an environmental risk (in many cases, a chemical exposure) and determining how large that risk is to humans.  It consists of four steps: (1) hazard identification, (2) dose-response assessment, (3) exposure assessment, and (4) risk characterization.  I will discuss each in future posts.

So why is human health risk assessment important?  Well, chemicals are a part of life.  Some exist naturally; some are made by humans and can be released to the environment.  They bring benefits to our lives, but like most things, they also come with risks.

Let’s consider a hypothetical example.  Suppose a factory produces something you use every day.  To make this product, the company uses several different chemicals, and some chemicals are produced during the manufacturing process as byproducts.  Some are released to the air and water and may get into the soil.  Let’s say this industrial site is located next to a river that leads to your local drinking water plant.  Are any of the chemicals in that water?  Are the levels safe for you to drink?  What about your child? What levels of the chemicals are safe for you to breathe?

Human health risk assessment helps answer questions like these.  It is a tool that helps local, state and federal governments make decisions about what levels of chemicals can be in drinking water; what additional controls are needed to keep levels emitted to the air at a safe level; and what levels need to be achieved to clean up a contaminated site.  From a public health perspective, this is pretty important stuff.

In the coming weeks, I’ll be posting more about EPA’s human health risk assessment work. Stay tuned for those posts, but in the meantime, you can learn more by going to

About the Author: Kacee Deener is the Communications Director in EPA’s National Center for Environmental Assessment.  She joined EPA 13 years ago and has a Masters degree in Public Health.