Abstract

Background
Indoor firing ranges are globally recognized as high-risk settings for occupational and recreational lead exposure due to the use of lead-based ammunition and frequently inadequate ventilation systems. In Korea, however, public health surveillance and regulatory oversight have remained limited. This case series empirically demonstrates that in high-emission settings like indoor firing ranges, ventilation upgrades are insufficient. Source substitution with lead-free primer ammunition proved to be the only definitive intervention.
Case Presentation
In late 2023, an index case presenting with abdominal pain was found to have a blood lead level (BLL) of 55 µg/dL, prompting a government-mandated investigation. Nine male shooting instructors (tenure: 4–65 months) were subsequently identified with BLLs ranging from 38.2–73.2 µg/dL, while airborne lead concentrations (ALC) reached 0.51 mg/m³—10 times the occupational exposure limit (OEL: 0.05 mg/m³). During a three-month closure to upgrade ventilation, workers received chelation therapy (CaNa₂EDTA and D-penicillamine), which reduced their BLLs to 3.2–25.7 µg/dL. However, two months after reopening, post-intervention ALC remained elevated at 0.0797 mg/m³, still exceeding the OEL, and BLLs rebounded to 16.2–53.3 µg/dL. A substitution strategy was then implemented, replacing lead-based ammunition with copper-clad, lead-free primer rounds. This intervention decreased ALC to <0.003 mg/m³ and lowered BLLs to 4.9–23.1 µg/dL. Despite the reduced airborne concentrations, several workers continued to exhibit BLLs around 20 µg/dL, suggesting subtle ongoing exposure and mobilization of bone-stored lead.
Conclusions
This cluster demonstrates that in environments where hazardous agents are continuously generated, such as indoor firing ranges, engineering controls alone, such as improved ventilation, may not provide adequate protection. Substitution—the most effective intervention within the hierarchy of controls—was essential for eliminating exposure. Furthermore, the toxicokinetics of bone lead in chronically exposed adults highlight the need for ongoing monitoring and cautious decision-making regarding treatment and return-to-work planning.

• Keywords: Lead poisoning; Indoor firing range; Occupational exposure; Chelation therapy; Hierarchy of controls; Lead-free ammunition