Understanding PPM (Parts Per Million)
PPM or Parts Per Million is a term used to define tiny amounts of material within other material.
PPM in Paint: Milligrams Per Kilogram
1 part per million is 1/1,000,000 while 1000ppm is 1000/1,000,000. When we are thinking about paint, it's helpful to think of it in terms of milligrams per kilogram since 1Kg is 1,000,000 Mg. So 1000 PPM is 1000 milligrams per kilogram.
PPM in Volume or Quantity
However, PPM could also define how much something is of volume or even something like grains of rice. For example, 1000 red grains of rice out of 1,000,000 is 1,000PPM.
Measuring Lead in Paint Using PPM
It's a great way to measure tiny amounts. For example, the limit in modern paint is 90 parts per million lead. This can be determined by a weighted sample, being digested with acid in a beaker, and then run through a laboratory machine which will visualize to the computer's hardware the amount of lead that is present in the sample.
PPM as a Rubric for Contamination Levels
Parts Per Million gives us an easy rubric which we can understand levels of contamination.
Historical Context of Lead Limits in Paint
In 1978, the Consumer Product Safety Commission (CPSC) banned the use of lead paint with more than 600 PPM lead by weight in residential properties and on products marketed for children.
Strengthening Lead Limits: CPSIA of 2008
In 2008, this rule was strengthened when the limit was lowered to 90 by the Consumer Product Safety Improvement Act (CPSIA). This act lowered the limit for lead in children's products to 0.009% (90 PPM) by weight.
The Challenge of Eliminating Lead in Commerce
These are relatively recent updates; 2008 seems like yesterday. This shows how difficult it is to get lead out of commerce! Lead-containing paints could have been sold in the US legally up until 2008—it's no wonder the EPA limit won't budge down from 5000 parts per million.
Modern Paints and Lead Safety
I don't want to be alarmist; modern paints that are not deteriorating and aren't being sanded or ingested are not nearly the threat that old lead-based paint is. However, any lead that adds to our "lead burden" is bad, as lead can contribute to hypertension leading to death in adults and obviously the permanent brain effects in children.
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