Evaluation of pulmonary function within a cohort of flavorings workers.

OBJECTIVES: We present a re-analysis of a recent Health Hazard Evaluation (HHE) that was performed by the US National Institute for Occupational Safety and Health (NIOSH) regarding the pulmonary status of workers at a flavorings manufacturing facility. This facility has used acetaldehyde, acetoin, benzaldehyde, butyric acid, diacetyl and many other flavoring chemicals for many years. METHODS: Ten years of spirometry testing and job descriptions data on 112 workers were analyzed by the authors and by NIOSH. Using NIOSH's exposure assessment criteria, we compared the prevalence of restrictive findings (as determined by spirometry testing) in production workers to an internal control group that had reduced or no potential for exposure to flavoring chemicals. NIOSH used multiple linear regression to evaluate changes in pulmonary function by the exposure group. After our review of the NIOSH findings, we evaluated associations between longitudinal changes in pulmonary health and workplace exposures through the use of generalized estimating equations. We then compared our results to those obtained by NIOSH. RESULTS: We found that the prevalence of pulmonary restriction was similar in production workers and internal controls. We found no relationship between the magnitude of exposure to flavorings chemicals and observed decrements in pulmonary function. Our findings were contrary to those reported by NIOSH, most likely because of how we accounted for the longitudinal nature of the spirometric data. CONCLUSION: Many years of exposures to flavoring chemicals in this workplace, including diacetyl, were not found to produce an increased risk of abnormal spirometric findings.

Incomplete homogenization of 18 S ribosomal DNA coding regions in Arabidopsis thaliana.

BACKGROUND: As a result of concerted evolution, coding regions of ribosomal DNA sequences are highly conserved within species and variation is generally thought to be limited to a few nucleotides. However, rDNA sequence variation has not been systematically examined in plant genomes, including that of the model plant Arabidopsis thaliana whose genome was the first to be sequenced. FINDINGS: Both genomic and transcribed 18 S sequences were sampled and revealed that most deviation from the consensus sequence was limited to single nucleotide substitutions except for a variant with a 270 bp deletion from position 456 to 725 in Arabidopsis numbering. The deletion maps to the functionally important and highly conserved 530 loop or helix18 in the structure of E. coli 16 S. The expression of the deletion variant is tightly controlled during developmental growth stages. Transcripts were not detectable in young seedlings but could be amplified from RNA extracts of mature leaves, stems, flowers and roots of Arabidopsis thaliana ecotype Columbia. We also show polymorphism for the deletion variant among four Arabidopsis ecotypes examined. CONCLUSION: Despite a strong purifying selection that might be expected against functionally impaired rDNAs, the newly identified variant is maintained in the Arabidopsis genome. The expression of the variant and the polymorphism displayed by Arabidopsis ecotypes suggest a transition state in concerted evolution.