What's Wrong With The CDC's Final Report On Formaldehyde In The FEMA Trailers? (Issued 2 July 2008)

While I'm pleased with the main finding that the geometric mean level of formaldehyde in the 519 sampled trailers was 77 parts-per-billion (ppb)--well below the 100 ppb level generally considered to be the point at which sensitive individuals report symptoms--there are still significant issues with several aspects of the testing.

The analytical method utilized, a NIOSH wet-chemical method, is not well suited to this application.  For one thing, it is not particularly accurate (± 19%).  For another, the method required air sampling for one hour at a given spot in the trailer, and this might not be truly representative, and does not allow testing of potential point sources, such as cabinetry.  For these two reasons alone, a direct-reading instrument would have been a far better choice than wet chemistry.

Further, it is unclear if appropriate temperature corrections were made, given that the trailers tested ranged from 41 to 91 degrees F.  Finally, the NIOSH method is affected by ozone, a compound that could have been present in some of the trailers.

Regrettably, some officials who should know better seem to prefer wet chemical over instrumentation methods, although in many cases, the instrumentation methods are far superior.

Surprisingly, no correction was made for cigarette smoke in the air, even though it is known that this smoke contains formaldehyde.  It would have been quite simple to also monitor the air for a marker for cigarette smoke, and exclude these trailers from the final results.  Instead, the CDC merely relied on survey answers from the occupants regarding their smoking habits, but did nothing to adjust the air monitoring data for this potentially confounding effect.

Despite the disclaimer that "it was not a health study," one wonders why not a single health question appeared on the Interviewer Questionnaire.  It would surely have been valuable to correlate measured concentrations with reported symptoms, even in the most generic manner.  After all, this entire study was driven by media horror stories of supposedly drastic health effects.

More than that, it is standard practice in any monitoring study, especially one clearly devoted to obtaining data in response to complaints from people in an occupancy, to catalog those complaints.  A health study could be done later, and would build on this data.  The absence of any symptom questions is a serious omission.

As such, the CDC final report will probably do little to silence the plaintiff's attorneys and Green activists.