Inhalation risk assessment of naphthalene emitted from deodorant balls in public toilets

The inhalation of naphthalene used as deodorant balls in public toilets could be an important cancer risk factor. The atmospheric concentration of naphthalene in public toilets (Cin) was estimated both by a polyurethane foam passive air sampler (PUF-PAS) deployed in nine public toilets in Seoul, Korea and by a steady-state indoor air quality model, including emission estimation using Monte-Carlo simulation. Based on the estimated Cin, cancer risk was also assessed for cleaning workers and the general population. The steady-state Cin estimated using the estimated emission rate, which assumed that air exchange was the only process by which naphthalene was removed, was much greater than the Cin value measured using PUF-PAS in nine public toilets, implying the importance of other removal processes, such as sorption to walls and the garments of visitors, as well as decreased emission rate owing to wetting of the naphthalene ball surface. The 95 percentile values of cancer risk for workers based on the estimation by PUF-PAS was 1.6×10^–6, whereas those for the general public were lower than 1×10^–6 . The results suggested that naphthalene deodorant balls in public toilets may be an important cancer risk factor especially for the cleaning workers.