A great many papers have been published on the topic of how to incorporate
'nondetects', low-level values reported only as below a detection limit, into
statistical analyses. This is of interest not only in occupational hygiene but
also in environmental sciences and astronomy, among other fields. In an article
published recently by the Annals of Occupational Hygiene, the literature is
reviewed from the earliest known publication on the topic >40 years ago and
recommendations contrasted. The author has tried to pull some unifying
conclusions out of the mix, ending with four suggestion.

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AplusA-online.de - Source: Annals of Occupational Hygiene