Generally, carbon monoxide (CO) toxicity is considered to be strictly acute.
That is, the adverse effects occur close to the time of exposure, are
reversible and are not cumulative unless there is significant neurologic
(brain) damage resulting from a massive exposure. In that case, the damage
can be permanent and sequelae can occur days after the cessation of exposure.
I recall reading about claims of adverse (cardiovascular) effects from
chronic low level exposures which would be expected to have little or no
acute toxicity. This was a bunch of years ago, and at the time these
speculations were considered quite controversial. A quick look at Casarett
and Doill's Toxicology (4th ed., 1991) doesn't show any discussion of such
Alan H. Stern, Dr.P.H., D.A.B.T.
New Jersey Dept. Environmental Protection
Univ. Medicine and Dentistry of NJ