File-Temp errors in apache logs - cannot delete temp directory

I’m using RT 3.4.5 and it’s all working fine except I notice a lot of
lines like this in the Apache logs:

Can’t remove directory /tmp/vPv8lB4xKh (Directory not empty) at
5.8/lib/5.8.7/File/ line 898

There are a lot (1500+) of these directories in /tmp now … the
permissions seem fine:

drwx------ 2 apache apache 4096 Apr 20 10:57 .
-rw-r–r-- 1 apache apache 198 Apr 20 10:57 part-24501-6.txt
-rw-r–r-- 1 apache apache 2420 Apr 20 10:57 part-24501-7.html

Anybody else seen this?

Philip Kime