Proposal for a revised reference concentration (RfC) for mercury vapour in adults

Area of Science:

• Environmental Health
• Toxicology
• Occupational Health

Background:

• Millions globally work in small-scale gold mining, facing significant mercury vapor exposure.
• Mercury exposure poses serious health risks, particularly in artisanal and small-scale gold mining (ASGM) communities.

Purpose of the Study:

• To investigate the health impacts of mercury vapor exposure in adults from gold mining areas.
• To establish reliable cut-off values in biological samples for mercury exposure.
• To derive proposed reference concentrations for mercury vapor in ambient air.

Main Methods:

• Medical investigations of 306 exposed adults and 58 unexposed volunteers in Zimbabwe and Tanzania.
• Analysis of mercury levels in blood, urine, and hair samples.
• Evaluation of 50 anamnestic and clinical signs/symptoms, with multivariate analysis and ROC curves to determine exposure thresholds.

Main Results:

• Identified specific mercury concentration cut-off values in urine (e.g., 4.7 µg Hg/g crea for ataxia, 3.6 µg Hg/g crea for sadness).
• Derived a lowest observed adverse effect level (LOAEL) for mercury vapor in air of 3.5 µg Hg/m³.
• Proposed reference concentrations (RfC) for ambient air: 0.1 µg Hg/m³ (US EPA analogy) and 0.07 µg Hg/m³ (European analogy).

Conclusions:

• Established scientifically-backed reference values for mercury vapor in ambient air.
• Highlights the need for stricter mercury exposure limits in small-scale gold mining regions.
• Provides crucial data for public health policies and risk management strategies concerning mercury pollution.