Establishment of Exposure Guidelines for Lead in Spacecraft Drinking Water
Garcia HD, Tsuji JS, James JT. Establishment of exposure guidelines for lead in spacecraft drinking water. Aviat Space Environ Med 2014; 85:715–20.
Background: Setting Spacecraft Water Exposure Guidelines (SWEGs) for lead (Pb) in spacecraft drinking water has special challenges related to estimating the increase in blood lead levels (PbB) due to the release of lead to systemic circulation via microgravity-induced bone loss. Methods: The effects on the PbB of lead in drinking water (PbW) and lead released from bones, and changes in lead exposure before, during, and after spaceflight, were evaluated using a physiologically based pharmacokinetic model that incorporated environmental lead exposure on Earth and in flight and included temporarily increased rates of osteoporosis during spaceflight. Results: The model predicts that in 2030 (the earliest potential launch date for a long-duration mission), the average American astronaut would have a PbB of 1.7 μg dl−1 at launch and that, while in microgravity, PbB levels would decrease at PbW values less than about 9 μg · L−1 because of reduced exposure within the spacecraft to environmental lead. Astronauts with high concentrations of lead stored in bones could experience increases in PbB due to microgravity-accelerated release of lead from bones. While the resultant in-flight PbB would depend on their preflight bone lead levels, their PbB will not be significantly further elevated (< 1 μg dl−1) by consuming water with a PbW of ≤ 9 μg dl−1. Selection of a SWEG that would not result in an increase in blood lead is prudent given uncertainties about health effects at low exposures. Conclusion: A SWEG of 9 μg · L−1 would protect astronauts on long-duration spaceflights by ensuring that PbB values will not exceed prelaunch levels.
Background: Setting Spacecraft Water Exposure Guidelines (SWEGs) for lead (Pb) in spacecraft drinking water has special challenges related to estimating the increase in blood lead levels (PbB) due to the release of lead to systemic circulation via microgravity-induced bone loss. Methods: The effects on the PbB of lead in drinking water (PbW) and lead released from bones, and changes in lead exposure before, during, and after spaceflight, were evaluated using a physiologically based pharmacokinetic model that incorporated environmental lead exposure on Earth and in flight and included temporarily increased rates of osteoporosis during spaceflight. Results: The model predicts that in 2030 (the earliest potential launch date for a long-duration mission), the average American astronaut would have a PbB of 1.7 μg dl−1 at launch and that, while in microgravity, PbB levels would decrease at PbW values less than about 9 μg · L−1 because of reduced exposure within the spacecraft to environmental lead. Astronauts with high concentrations of lead stored in bones could experience increases in PbB due to microgravity-accelerated release of lead from bones. While the resultant in-flight PbB would depend on their preflight bone lead levels, their PbB will not be significantly further elevated (< 1 μg dl−1) by consuming water with a PbW of ≤ 9 μg dl−1. Selection of a SWEG that would not result in an increase in blood lead is prudent given uncertainties about health effects at low exposures. Conclusion: A SWEG of 9 μg · L−1 would protect astronauts on long-duration spaceflights by ensuring that PbB values will not exceed prelaunch levels.
Keywords: PBPK models; SWEG; blood lead; bone lead; lead; microgravity; osteoporosis; spaceflight
Document Type: Research Article
Affiliations: Wyle Science, Technology and Engineering Group, Houston, TX, USA
Publication date: 01 July 2014
- The peer-reviewed monthly journal, Aviation, Space, and Environmental Medicine (ASEM) provides contact with physicians, life scientists, bioengineers, and medical specialists working in both basic medical research and in its clinical applications. It is the most used and cited journal in its field. ASEM is distributed to more than 80 nations.
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