=chemistry =chemical safety =regulation =paint
Release of volatile organic
compounds is regulated, largely because they react with air in sunlight to
produce smog.
However, if a compound doesn't evaporate very much,
then it's exempt from those regulations. Specifically:
Under EPA
regulations, a chemical is VOC-exempt, if it:
- Has vapor pressure of
less than 0.1 millimeters of mercury (at 20 degrees
Celsius); Or, if the
vapor pressure is unknown:
- Consists of more than 12 carbon atoms; or
- Has a melting point higher than 20 degrees C. and does not sublime
This seems reasonable, but the result has been companies making large
amounts of compounds with vapor pressure just below the regulatory limit,
and people spreading them thinly on large surfaces. I'm talking, of course,
about paint.
Companies
are producing paints that dry slower than they need to, that are more
expensive than they need to be, and release more-toxic compounds than they
should, all to meet this vapor pressure threshold to be VOC-exempt even
though that shouldn't matter at all. If you've ever been annoyed by paint
drying slowly, or felt like paint fumes were particularly noxious, that's
partly thanks to how VOC regulations are designed.
If you have chemicals that are going to evaporate
entirely, it doesn't matter if they do so quickly or slowly. The VOC
regulations weren't designed for paints. But of course, nobody
really wants to change the current situation. The EPA doesn't want to ban most current paint
compositions. Industry doesn't want to switch to making different chemicals.
Consumers don't have time to think about this stuff and mostly don't care.
(Even if you do happen to care, companies don't tell you what chemicals are
in their paints.)
So, here we are.
As for what companies should be using in paint? If cheaper production of levulinic acid from biomass happens, then companies should use ethyl levulinate. For now, maybe butyl lactate. Those are, at least, good solvents that are relatively nontoxic - they're just slightly too volatile to be VOC-exempt.