After reading all of the postings regarding your question, it is apparent
that there is a considerable amount of interest in acetone. It also appears
that your original question has not been addressed. As you know, a small
group of us have been working with EPA on the petition to delist ink oils as
a VOC. In the discussions with EPA, the issue regarding acetone has been
discussed. At this point in the review of EPA's policy of photochemical
reactivity and how it is defined, it appears that acetone will remain on the
list of exempt compounds. EPA did not mention any plans to take acetone off
the list of exempt compounds.
In the discussions with EPA on how photochemical reactivity is defined,
acetone should be viewed as an anomaly. While it seems to be certain that
ethane will be used as the benchmark for comparison, the measure of
reactivity has gone through some changes. In the decision to delist acetone,
EPA used the gram basis to justify its decision. The gram basis looks at the
weight of ozone produced per weight of test compound compared. The other
measure is molar, which is best thought as a concentration and not weight.
Since the vast majority of chemical reactions are examined on a molar basis,
mole comparisons are more scientifically acceptable. It is interesting to
note that on a molar basis acetone produces more ozone than ethane.
When EPA delisted acetone and those who follow this issue realized the
significance of the shift in policy from a molar to a weight basis, EPA was
flooded with petitions, including ours for ink oil. After the acetone
decision, EPA began to examine its revised policy and has decided that a
weight basis is far more difficult to defend and is not technically accurate.
Therefore, in the methyl acetate decision, EPA stated that only those
compounds that produce less ozone than ethane on a molar basis will be
considered for delisting. The good news for methyl acetate is that is less
reactive than ethane on both a molar and gram basis.
EPA has not yet decided what to do with those petitions that were submitted
as a result of the acetone decision that have compounds that are less
reactive on a gram basis, but more reactive on a molar basis. Ink oils fall
into this category.