5. The key issue is whether the assessment should be based on
exposures that had prevailed for about the last 6 years with a
NOAEL of a mean exposure of 39–49 ppm or alternatively
should the high/long exposure group be used to define a
NOAEL/LOAEL based on the LWAE of 25–33 ppm over about
15 years. But the LWAE is not a reliable quantitative indicator
for former high exposure levels. It is derived by the life time
exposure at different jobs divided by job tenure. This is in principle
an average over the total life time exposure situation and
high exposures in former years are insufficiently represented.
Therefore the LWAE is only suited to a very limited extent to
define a NOAEL/LOAEL that stems from high exposures over
limited time periods in former years.