Chronic health effects of recurrent indoor Pyrethroid exposure in enclosed workplaces: an occupational exposome–based clinical review in the context of limited safety guidance

Pyrethroid insecticides are widely used indoors in residential, commercial, and occupational pest-control settings and are generally regarded as safe because of their relatively low acute toxicity. This perception is largely based on short-term exposure data and application practices conducted under well-ventilated conditions. However, indoor pesticide application does not always occur in environments that allow for rapid residue clearance. In enclosed workplaces—particularly those with centralized heating, ventilation, and air-conditioning systems, limited fresh-air exchange, and dust-retaining surfaces such as wall-to-wall carpeting—pyrethroid residues may persist beyond the initial application period. These residues may accumulate in indoor dust and textiles and undergo resuspension, potentially resulting in recurrent low-level exposure. In such settings, exposure may involve not only pest-control personnel but also other workers who are not considered pesticide-exposed and are not routinely monitored. From an occupational health perspective, this article draws on published environmental, biomonitoring, and clinical literature to discuss how building characteristics, residue persistence, and ventilation conditions may represent overlooked contributors to indoor pyrethroid exposure. Reported findings include neurologic symptoms, endocrine alterations—particularly involving thyroid function—and mild hepatic enzyme abnormalities, although evidence remains heterogeneous and non-causal. No exposure measurements or case investigations are presented. The aim of this review is to raise awareness and encourage further research on indoor exposure dynamics and workplace evaluation of indoor pesticide use. The reviewed evidence indicates that indoor environments may sustain prolonged low-level exposure through reservoirs such as dust, carpets, and ventilation systems. Mechanistic data support potential multisystem involvement, while human studies suggest associations with neurological, endocrine, and hepatic changes, although findings remain variable and non-causal.