Projected uptake and toxicity of selenium compounds from the environment

Area of Science:

• Environmental Health
• Toxicology
• Biomathematics

Background:

• Industrial workers and the public can be exposed to selenium via inhalation or ingestion.
• Selenium's impact on body tissues requires understanding its transport and accumulation.
• Previous studies involved animal models with radiolabeled selenium compounds.

Purpose of the Study:

• To develop and validate a model for selenium uptake in human tissues.
• To assess selenium distribution from inhalation and ingestion exposure routes.
• To predict equilibrium organ concentrations in humans under continuous exposure.

Main Methods:

• A compartmental model was created for lung, GI tract, blood, liver, and other tissues.
• Model simulations were validated against rat and dog inhalation exposure data.
• The model was adapted to predict human tissue concentrations based on daily intake and air levels.

Main Results:

• Dietary intake is the dominant source of selenium for most people at low air concentrations (1 ng Se/m3).
• Inhalation of selenium at the threshold limit value (200 µg/m3) significantly increases total body burden.
• Predicted lung, liver, and blood selenium levels at TLV were 22,000, 1200, and 440 ng Se/g tissue, respectively.

Conclusions:

• Dietary selenium is generally more significant than atmospheric exposure for total body burden.
• Continuous inhalation at the TLV can lead to substantial selenium accumulation, particularly in the lungs.
• Predicted lung concentrations at TLV approach levels associated with toxicity in animal studies.