David Kirkland

For non-pharmaceuticals the current data suggest it may not be necessary to test to 10 mM top concentration for non-toxic chemicals in all circumstances

Whilst the data are not sufficient to recommend a new specific top concentration (as 1 mM has been recommended for pharmaceuticals), several possible approaches are under discussion:-

1 mM may be acceptable for routine testing ◦ Except for low molecular weight substances,

chemicals with high (particularly local) exposure, and complex mixtures or technical grade materials

2 mM may be acceptable for routine testing, based on the current (incomplete) analysis of published data◦ Similar exceptions to above may apply

A top concentration of 1000 µg/ml or 10 mM (whichever is the lower) may be acceptable◦ Low MW chemicals would be tested to 10 mM but

many chemicals would be tested to about 4 mM

Complete testing of “chemicals of concern” from ECVAM/Parry analysis (including chlorobenzene, 2- mercaptobenzothiazole, furfural?)◦ Are there any further chemicals from the “probably

non-genotoxic” list that need to be re-tested? Re-analyse ECVAM/Parry data in terms of

1000 µg/ml or 10 mM proposal Complete analysis of “acceptability” of NTP

MLA data and see how this affects the list of 23 “chemicals of concern”