Gap DUST 11: What is the potential for acute toxicity of lunar dust (all relevant endpoints), and acute/chronic cardiovascular toxicity of lunar dust? (Previous title: AEH 11)
Last Published:  07/30/21 01:05:31 PM (Central)
Responsible Element: Exploration Medical Capability (ExMC)
Status: Closed
Closure Rationale
Sufficient knowledge exists with respect to cardiovascular toxicity of lunar dust exposure. A Permissible Exposure Limit (PEL) for lunar dust has been defined and subsequently (https://humanresearchroadmap.nasa.gov/gaps/closureDocumentation/Lunar%20Dust%20Toxicity%20FINAL%20REPORT.pdf?rnd=0.186300978616951), the NASA Standard has been updated (https://www.nasa.gov/sites/default/files/atoms/files/nasa-std-3001_vol_2_rev_b.pdf). 
Closure Documentation:
No Closure Documentation Available
Description

Extensive research was performed to establish a permissible exposure limit (PEL) for average exposure to lunar dust over the course of a 6-month mission. The gap that remains is to determine the acceptable short-term excursions that do not violate the average but may cause acute toxicity.

Specifically, much evidence has been accumulated that demonstrates that the respiratory system is not the only system that experiences deleterious effects as a result of inhalation of particulate matter (PM). A link between PM in air and cardiovascular morbidity and mortality has been firmly established (Pope et al, 2004; Scapellato et al, 2007; Walker and Mouton, 2008). Pope (2008)) reported that long-term exposures to PM were most strongly associated with mortality attributable to ischemic heart disease, dysrhythmias, heart failure, and cardiac arrest. Oxidative stress initiated in response to inhaled particles is thought to lead to inflammation which in turn stimulates release from lungs into the circulation of pro-inflammatory mediators that promote systemic inflammation that exacerbates or establishes conditions that promote pathology at sites beyond the lungs (Seaton et al, 1995). More recently, studies with nanoparticles have indicated that effects distal to the lungs may originate locally in response to inhaled PM that has translocated from the lungs (Oberdorster et al., 2002, 2004; Nemmar et al., 2004; Borm et al., 2006; Mossman et al., 2007; Rothen-Ruthishauser et al., 2007), or by PM affecting respiratory reflexes or the autonomic nervous system (Gwin et al., 2006). The observation that inhalation of PM produces adverse effects at sites distal to the lungs, and the possibility that some of these effects may be caused by translocation of PM, particularly ultrafines, from the lungs, suggests additional gaps in the knowledge that we will require to fully assess the risk of adverse health effects posed by lunar dust.

In the Lunar Airborne Dust Toxicity Advisory Group (LADTAG) final report of February 7, 2014 cardiovascular risks were highlighted as an area for further risk assessment/research. This assessment was seconded by a recommendation received from the Standing Review Panel to include a new gap to assess the potential for acute or chronic cardiovascular toxicity of lunar dust. Gap Dust 11 acknowledges those recommendations.

In addition, there is evidence to suggest that celestial dusts have potential allergenic properties that may be exacerbated by spaceflight. Several recent studies have provided evidence of immune dysregulation during spaceflight (Mehta et al., 2007, 2013; Crucian et al., 2008, 2009, 2011, 2013), which may contribute to an increased potential for acute hypersensitivity reactions. Symptoms suggestive of an allergic response, which worsened with each exposure, were documented in a flight surgeon, who was exposed to lunar dust during post-mission handling of EVA suits (Scheuring et al., 2008).

Research Approach:

Utilize solicited or directed projects to assess the potential for acute toxicity across multiple endpoints as well as potential chronic cardiovascular toxicity of lunar dust. Collaborate with Immunology, Cardiology, Nutrition (Oxidative Stress), and Toxic Exposure Risk areas in terms of cross-disciplinary risk assessment.
Target for Closure
Closure of this gap is predicated on NASA identification of the lunar surface as a relevant mission objective. Currently, there is not a compelling need for more comprehensive lunar dust PELs that include consideration for cardiovascular risks or that describe exposure constraints due to acute dust exposure concerns. If a lunar surface return became a clear mission objective, closure of this gap would likely occur through a formal acute PEL development process (similar to what was accomplished with the current lunar PEL for chronic exposure). A renewed focus on lunar surface return would also prompt further risk characterization of cardiovascular endpoints, and an evaluation of the sufficiency of the protection afforded in applying the existing chronic lunar dust PEL of 0.3 mg/m3. If the chronic PEL was found to be inadequately protective, a lower chronic PEL might be necessary.
Mappings
Risk Risk of Adverse Health and Performance Effects of Celestial Dust Exposure
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Completed

Multi-Disciplinary Research Plans

Documentation:
No Documentation Available