Exposure study to examine chemosensory effects of ɛ-caprolactam in healthy men and women

Abstract

Context: ε-Caprolactam is an important industrial chemical with a relatively low human toxicity; of importance is the irritations that occur after exposure to ε-caprolactam as aerosols or vapors.

Objective: The aim of this study was to examine symptoms and objective effects, which occur on the mucous membranes of the eyes and the upper respiratory tract.

Methods: A total of 52 healthy volunteers (26 women and 26 men, aged between 19 and 50 years) were exposed by random to different ε-caprolactam concentrations (0.05, 0.5 and 5.0 mg/m³) and the control condition (0.0 mg/m³) for 6 h on four consecutive days. Eye blinking frequency, tear film break-up time, eye redness, nasal flows and resistance, olfactory function as well as total protein and interleukin-8 in nasal lavage fluid were determined daily before, during and after exposure. Questionnaires were used to record both subjective symptoms and personality factors.

Results: There were no significant specific effects on the subjective and objective endpoints examined. Statistical analysis yielded no evidence of concentration-response relationships. Evaluation of olfactory symptoms showed that the duration of the stay in the chamber and not the ε-caprolactam concentration was decisive for the perception of “impure air”. Personality factors had no significant influence on the reported symptoms.

Conclusions: Exposure to ε-caprolactam concentrations of 5.0 mg/m³ at maximum for 6 h did not cause chemosensory effects on the upper respiratory tract or eyes of healthy volunteers. Therefore, the concentration of 5.0 mg/m³ corresponds to the No Observed Adverse Effect Level (NOAEL).

Keywords:

• Caprolactam
• chemosensory effects
• exposure study
• eye blinking frequency

Acknowledgements

First of all, we would like to thank the participants and all coworkers, namely M. Dollinger, J. Hildenberg, J. Martin and A.S. Dammert, for their support in preparing and carrying out the examinations. We are indebted to the sponsors mentioned below, to Prof. Dr. M. Raulf (IPA, Bochum, Germany) for the analysis of the NALF parameters and her helpful comments on the results and to J. U. Mueller for his assistance in preparing this manuscript.

Declaration of interest

For this study, Prof. Dr. G. Triebig received grants from the European Caprolactam and Fiber Producers, the US Carpet and Rug Institute (CRI ™) and the Verein zur Förderung der Arbeitsmedizin an der Universität Heidelberg. The sponsors did neither influence the performance and analysis of this study nor its publication. I. Triebig-Heller and T. Bruckner have nothing to disclose.