Levels of Concern for Air Toxics

Now you know what levels of toxic chemicals are in the air that you breathe.
Figure out what they mean using our Levels of Concern look-up program.
Skip the explanations and go straight to Levels of Concern Lookup


Taking samples with buckets can get your community valuable information about what's in the air that you're breathing. But how do you know what the levels of chemicals in your air mean to your health?

One way of interpreting monitoring results--from either bucket samples or monitoring done by agencies--is to compare them to what we call "levels of concern."
Some levels of concern are levels that state governments have designated as the maximum levels of toxics that are allowed to be in the air. These levels are called "standards" and are legally enforceable in states that have them.

Other levels of concern are developed by government agencies which survey scientific studies to figure out what levels of chemical exposure pose minimal risk to your health. The agencies consider these levels (called "screening levels" or "minimum risk levels") as something like a borderline between levels of chemical exposure that could do you harm and levels that probably won't do you any harm. They are not legally enforceable.

This page looks up Levels of Concern for chemicals that you are interested in and compares them to results you have from monitoring. The report it generates tells you whether any of the levels of chemicals in your air are above the levels of concern.

Remember: Levels of Concern are only part of the story. There are limitations to what is known about the health effects of chemicals. There may be health impacts associated even with levels of chemicals below the levels of concern.
(Watch here for more information about the holes in data on chemicals and health impacts!)

The information on this site is not intended to be legal advice. This information is not a substitute for the advice of an attorney admitted to practice in the relevant jurisdiction. Persons using this site should not take or refrain from taking legal action based solely on information provided on this site or generated by using the tools on this site.



To look up Levels of Concern:

1. Enter the name of your organization or sample.
This will be used in the titles of your report.

Line 1:
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2. Choose your units.

What units would you like your report (output) in?

What you choose here will determine whether the numbers in the report will be expressed in ppb, ug/m3, or ppbv. For example, if you choose ppb, you will see both your monitoring results and the levels of concern in terms of ppb. You should choose whatever units you are most comfortable with as the units for your final report.


What units are your measured values (input) in?

Here you should choose the units that the results from your monitoring were reported in. Choose only one type of units for all of the chemicals and values that you will enter in the table below.
For example, bucket results are in both ug/m3 and ppbv. If there are TICs (tentatively identified compounds), those are reported in ug/m3. It makes sense, then, to choose ug/m3 if you are using bucket results.

What are "units"?

Units give meaning to the numbers we use to describe quantities.

For instance, if someone asked you how long something was, you might say 12 inches or 1 foot or 30 centimeters. "Inches," "feet," and "centimeters" are all units that we use to measure length. Those three answers all mean the same thing even though they are different numbers (12, 1, and 30) because they use different units of measurement.

When we talk about levels of chemicals in the air, we are talking about concentrations. While length is measured in inches and centimeters, concentrations are commonly measured in Parts per Billion (ppb), or Micrograms per Meters Cubed (ug/m3).

Parts per billion (ppb) describes how many parts of a chemical are in the same space as 1 billion parts of air. So 3ppb means there are 3 parts chemical for every 1,000,000,000 parts of air.
Usually ppb are figured out in terms of the weight of chemical and air molecules. But where you see ppb by volume or ppbv, that means the concentration has been figured out in terms of volume, or how much space the molecules take up. This is a less common meaning of parts per billion.

Micrograms per Meters Cubed (ug/m3) describes how much of a chemical--by weight--is in a volume of air that takes up one cubic meter. Imagine a box filled with air that measures one meter on every side. If there were 3 micrograms, or 3 millionths of 1 gram, of chemical in that box, then the concentration would be 3ug/m3.

(Source: The Bucket Brigade Manual, p. 26)


3. Enter chemicals of interest and their measured levels.
If you are working from bucket results, enter the chemicals for which there was a measurable concentration (instead of ND).
You should be able to use common synonyms for the chemicals.
Be sure that all of the values you enter are in the units that you selected for "measured values" or "input" above.


Chemical Name Measured Value


4. Optional: Choose to show regulatory standards only.
The Louisiana and North Carolina Ambient Air Standards are legally enforceable levels of concern. If you live in one of these states, you may want to look only at the legal limits which apply to you.
If you don't check one of these boxes, you will see standards and screening levels from all over the country.

Only look at the Louisiana Ambient Air Standards.
Only look at the North Carolina Ambient Air Standards.




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