Occurrence, dermal and unintentional ingestion exposure, and human health risk of additives and chemical allergens in commercial mouse pads

Prolonged frictional contact between mouse pads and human skin occurs repeatedly in daily life, but occurrence and potential hazards of additives and chemical allergens in commercial mouse pads remain poorly understood. To address this knowledge gap, the present study evaluated five classes of additives in 70 commercial mouse pads from China. Target metal(loid)s exhibited the highest concentrations (42-120000 μg g^-1), followed by vulcanizing accelerators (0.1-2100 μg g^-1), benzothiazoles (0.1-1400 μg g^-1), plasticizers (1-310000 μg g^-1), and phenylenediamines (0.1-100 μg g^-1). Skin sensitizers (0.1-2100 μg g^-1) and regulated nitrosatable substances (0.3-22 μg g^-1) were also identified, particularly in the mouse pads for general usage, e-sports, and rubber-type. Mouse pads with infrared heating (1800-310000 μg g^-1) contained more abundant target chemicals than those for general usage (73-160000 μg g^-1) and e-sports (150-120000 μg g^-1). Estimated daily exposure doses of the target chemicals via dermal contact and inadvertent hand-to-mouth ingestion were comparable. Unintentional hand-to-mouth ingestion with heated mouse/desk pads and leather mouse pads poses significant non-carcinogenic risk, but insignificant risk with other mouse pads. However, given the widespread occurrence of a variety of additives in mouse pads, particularly those that cause skin sensitization concerns, adoption of green and low/non-skin sensitizers in mouse pads is highly desirable.