Objectives: The objective of this study is to
examine eye irritation in human volunteers
exposed to formaldehyde concentrations
between 0.15 and 1.0 ppm.
Methods: Testing is conducted in 21 nonsmoking
volunteers (11 males, 10 females,
aged 19 to 39 years) during six days. Each
subject is exposed to formaldehyde concentrations
of 0.15 ppm, 0.3 ppm and 0.5 ppm
for 4 hours. To simulate discontinuous working
situations, peak exposures of 0.6 ppm or
1.0 ppm, each for 15 minutes, are included.
Study parameters are: conjunctival redness
(slit-lamp photography) and blinking frequency
(video recording). To record the subject’s
physical and mental state, the validated
SPES questionnaire is used. The PANAS
questionnaire is used to investigate the influence
of personality traits on subjective
ratings.
Results: The subjective ratings indicate eye
irritation at concentrations as low as 0.3 ppm.
Blinking frequency which is the most sensitive
objective parameter, is increased significantly
by short-term peak exposures of
1.0 ppm during baseline exposure to 0.5 ppm
formaldehyde. Conjunctival redness, ranging
from slight to moderate on the CCLRU
ranging scale (Cornea and Contact Lens Research
Unit) increases significantly at concentrations
of 0.5 ppm with short-term peaks of
1.0 ppm.
The analysis of personality traits as a covariate
showed for volunteers who rate their
personality as “anxious”, that a “negative affect”
has a significant influence on the subjective
rating of irritation. Objective parameters
such as blinking frequency are not affected.
Conclusions: Blinking frequency is a sensitive
physiological parameter of formaldehyde-
induced conjunctival irritation. Significant
changes in blinking frequency occur at
concentrations of approximately 0.5 ppm
with a peak of 1.0 ppm. This reflects the lowest
observed effect level (LOEL). Personality
traits have a great effect on subjective rating
of irritation, the blinking frequency as an objective
parameter is not affected.
