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Every day, people are exposed to a variety of activities or products that could, under certain circumstances, cause harm. There’s a potential for harm or injury in nearly every activity we engage in – whether it’s when we cross a street, ride in an automobile, or play in a baseball game. This potential for harm can be referred to as “risk.”

The terms “risk” and “hazard” may seem to have very similar meaning to most of us, but to a scientist they are actually very different. With respect to chemistry, the terms have very specific meanings:

Hazard refers to the inherent properties of a chemical substance that make it capable of causing harm to a person or the environment.

Exposure describes both the amount of, and the frequency with which, a chemical substance comes into contact with a person, group of people or the environment.

Risk is the possibility of a harm arising from a particular exposure to a chemical substance, under specific conditions.

Here’s an example most people can relate to: Crossing the street presents the hazard of getting hit by a passing car. But risk is the likelihood of harm actually occurring. There might be no risk of getting hit by a car while crossing an empty street in the middle of the night, but a high risk in the middle of rush hour. There might be a very low risk of getting hit while crossing with the light in a crosswalk, but a high risk while jaywalking.

So to understand risk, we need to know both what the inherent hazard is (getting hit by a car) and the degree of exposure (the number of cars on the road). Once we understand risk, we can also reduce or manage it – for example, by requiring better marked crosswalks or managing traffic flow.

So what does risk mean in relation to the products we use every day, and the chemical ingredients used to make them?

What are hazardous or dangerous chemicals of concern?

First things first. It’s important to understand that everything around us, including the entire human body and everything we eat and drink, is entirely made of up chemicals. And all chemicals have inherent properties and can be described by hazard – even water and oxygen (it’s possible to drink too much water, and oxygen can explode).

Chemical ingredients found in everyday products are sometimes criticized as being harmful to human health. But, even though all chemicals can be described by inherent hazard, even water and oxygen, the mere presence of a chemical ingredient does not automatically mean it will cause harm. The actual chance of harm from exposure to a chemical ingredient depends on a variety of factors – including how much of the chemical ingredient is in a product; how the product is used; and what kind of exposure to the chemical typically occurs from using a product that contains the chemical.

How can we test for chemical exposure in everyday products?

There is a process by which chemical ingredients in consumer products can be assessed for safety, taking into account risk, hazard and exposure. Scientific experts at many government agencies use computerized evaluation procedures, data and testing to establish safe exposure levels for chemicals in certain regulated products. Companies producing consumer products are also responsible for the safety of the products they sell, and many do their own robust evaluations and safety testing.

Agency data and reviews help create an integrated web of safety information and assessment. For example, the U.S. Food and Drug Administration regulates the safety of materials in contact with food to the stringent safety standard of “reasonable certainty of no harm under the conditions of use.” For detailed technical information, consult the International Toxicity Estimates for Risk (ITER) database, which can be accessed via the National Library of Medicine’s website. ITER presents summary charts comparing risk assessment information from U.S. and international sources and explains the differences in risk values derived by these different organizations.

Understanding risk and how it’s assessed can seem complicated, but it’s the foundation of our ability to confirm the safety of chemicals as used in consumer products.