Human spaceflight inherently involves a high degree of known risks, as well as uncertain and unforeseeable risks. Risks to astronauts exist during all phases of any space mission, including terrestrial training and vehicle testing, launch, inflight during the mission, and landing. In fact, the launch of the spacecraft is known to be one of the riskiest times in any mission. Health risks during long duration and exploration spaceflights include short-term health consequences (e.g., nausea or fatigue from acute radiation exposure during a solar storm, injury, blurred vision) as well as long-term health consequences that arise or continue months or years after a flight (e.g., radiation-induced cancers; loss of bone mass) (see Chapter 3). The National Aeronautics and Space Administration’s (NASA’s) Human Research Program has identified 32 space-related health risks that are being studied for possible prevention, treatment, and mitigation approaches (NASA, 2013b). Health standards have been developed by NASA for a number of these risks to set limits on hazardous exposures, outline acceptable health parameters, and guide efforts to protect the health of crew members. This chapter begins with an overview of NASA’s approach to risk management and then details the health standards and the process used to develop those standards.
NASA RISK MANAGEMENT PROCESSES
NASA addresses health risks associated with spaceflight using a number of strategies, including engineering, design, mission planning, basic and clinical research, surveillance, medical monitoring, preventive and treatment countermeasures, and health standards. NASA has an ex-
tensive research portfolio—managed and implemented through the NASA Human Research Program, National Space Biomedical Research Institute, and other NASA directorates—designed to examine, prevent, and mitigate health and safety risks. The committee was not asked to review NASA’s risk management processes but rather to articulate ethics principles, decision points, and recommendations (see Chapters 5 and 6) that should guide health standard decision making surrounding long duration and exploration spaceflight missions and that could be integrated into risk management processes.
Risk management policy at NASA comprises two integrated efforts: risk-informed decision making and continuous risk management processes (NASA, 2008a; Dezfuli, 2013). These processes are used across the agency and apply to engineering, safety, and health standards. Risks are identified based on historical precedence (lessons learned and empirical data), on possible failures in laboratory tests, and in discussions with subject matter experts. Risks are extensively documented and, if possible, quantified. When risk is considered to be unacceptably high, alternative designs and missions scenarios are considered, and the risk assessment continues iteratively. This process is not unique to NASA and represents best practice across a number of industries (INSAG, 2011; FERC, 2013).
In new or emerging areas of concern about space-related health risks, risk assessment may first be based on expert opinion and then be informed by experience gained in a new environment or through case reports and lessons learned from prior space missions (e.g., vision impairment has recently been identified as a risk of spaceflight; see Chapter 3). NASA risk assessment processes initially use a wide margin of uncertainty that, with continued experience, is generally narrowed (Dezfuli, 2013). Decisions regarding the design and implementation of a mission are made based on a combination of available evidence and best risk estimates.
As a federal agency tasked with highly risky missions, NASA must make numerous decisions that balance health and safety risks, technological feasibility, and financial costs against mission necessity and the lost opportunity that comes when missions are not undertaken. NASA states, in part, “an adequately safe system is not necessarily one that completely precludes all conditions that can lead to undesirable consequences” (NASA, 2011c, p. 4). According to NASA policy, adequately safe systems follow two primary safety principles: (1) they meet a minimum threshold level of safety, “as determined by analysis, operating experi-
ence, or a combination of both” and aim to improve over time, and (2) they are as “as Safe as Reasonably Practicable” (ASARP) (NASA, 2011c, p. 4). An assessment of whether a system is ASARP involves weighing its safety performance against the impact of the changes that would need to be done to further improve it. “The system is ASARP if an incremental improvement in safety would require a disproportionate deterioration of system performance in other areas” (NASA, 2011c, p. 5). Moreover, informed decision making by those affected is an essential component (Dezfuli, 2013).
Similar to risk assessment for hardware and software, there is a risk assessment process for human health risks, and concomitant strategies for mitigating the risks. By necessity, these two processes are connected and iterative. For example, if radiation exposure in a particular mission is considered too high, this drives the design of the vehicle and the mission design. If there is no engineering or mission design solution to mitigate the risk, then other alternatives are considered, such as redesign of the mission, delays in the mission until technology is available, or making exceptions to the standards. The Bioastronautics Roadmap was developed by NASA as a framework for identifying and assessing the risks to spacecraft crews and included both health and medical risks, as well as engineering technology and system performance risks (NASA, 2005). In the roadmap, “risk” is defined as “the conditional probability of an adverse event from exposure to the space flight environment” and a “risk factor” as a “predisposing condition that contributes to an adverse outcome” (NASA, 2005, p. 3). Specific issues regarding risks were detailed in the roadmap as they pertained to three design reference missions: a 1-year tour of duty on the International Space Station (ISS), a month-long stay on the lunar surface, and a 30-month mission to Mars (NASA, 2005). Design reference missions describe the orbit, mission duration, environments, and proposed operations. There may be multiple design reference missions to a single destination, and each is assessed for challenges, benefits, and risks. These scenarios provide context for mission design and risk identification and assessment, and include information on potential transit times, communication lag times, microgravity-exposure and radiation-exposure levels, vehicle requirements, and the extent of proposed extravehicular activity. The design reference missions continue to be updated and several options for missions to a near-Earth asteroid have been proposed recently along with updates to the Mars design reference mission scenarios (see Table 2-1; NASA, 2009b, 2013c,e).
TABLE 2-1 Examples of NASA’s Design Reference Missions
|Possible Mission||Approximate Duration of Mission||Surface Stay||Crew Size|
|Mars||One proposed design is for approximately a 3-year mission (
||Short-stay missions: 30 to 90 days (
|Near-Earth asteroid (NEA)||One proposed design is for a 12- to 13-month mission with approximately 12 months of transit time and a 1-month stay (
||30 days for the year-long mission||3 for the year-long mission|
|International Space Station||365 days||Not applicable||2
|Lunar landing—outpost mission||Approximately 6 months with transit time of 4 days||Approximately 6 months||4|
NOTE: EVA = extravehicular activity.
aTwo crew members would be there for the full year. Other crew members would be there for shorter durations.
SOURCES: NASA, 2009b, 2013c,e.
In 2006, at the request of NASA, the Institute of Medicine (IOM) published a review of the Bioastronautics Roadmap (IOM and NRC, 2006). As part of this comprehensive review, the committee provided several recommendations with respect to format, evidence documentation, definition of specific risks, overarching risk categories (representing potential interaction among risks), and the reframing of risks as either health or technology related. The Bioastronautics Roadmap has since
evolved into the Human Research Roadmap, which categorizes 32 health risks into five categories: (1) behavioral health and performance; (2) human health countermeasures (which include bone metabolism and physiology, nutrition, immunology, cardiac and pulmonary physiology, and injury); (3) space radiation; (4) space human factors and habitability; and (5) exploration medical capabilities (NASA, 2013b; see Table 2-2). For each of the 32 areas, the Roadmap provides research reviews and ratings on risk mitigation and control, as discussed below. Chapter 3 provides brief overviews of several of the 32 risks to illustrate how widely the risks vary in the extent to which there are known preventive or treatment measures and to which vehicle or mission design might provide countermeasures.
Each of the risks has been rated by NASA for four design reference missions. The ratings indicate the state of knowledge on mitigating or controlling the risk to meet the NASA standards for maintaining crew performance and health. The ratings system categorizes the risks as: Controlled (C), Acceptable (A), Unacceptable (U), and Insufficient Data (I) (see Table 2-2) (NASA, 2013c). The state of research on each of the 32 risks is summarized in a set of evidence reports, with each report updated and reviewed on a regular basis (NASA, 2013b). These research reviews and ratings provide starting points for identifying gaps and research directions for NASA’s Human Research Program, and progress on this research is monitored by NASA’s Human System Risk Board. The IOM reviewed NASA’s processes for compiling and updating the evidence reports in 2008 (IOM, 2008), and the IOM is conducting a study that will review each evidence report (IOM, 2014).
A number of health risks are known and are mitigated, to the extent feasible, through prevention and intervention strategies, which are continuously evaluated for effectiveness. The seriousness of other likely risks is largely unknown. Still other risks have not been anticipated yet, and will only be uncovered by experience. Thus, setting health and performance standards for this wide array of risks is challenging.
TABLE 2-2 Human Health and Performance Risks with Research Ratings for Design Reference Missions
|HRP Research Rating|
|Risk of orthostatic intolerance during re-exposure to gravity||C||C||C||A|
|Risk of early onset osteoporosis due to spaceflight||A||A||A||A|
|Risk factor of inadequate nutrition||C||C||A||U|
|Risk of compromised EVA performance and crew health due to inadequate EVA suit systems||A||A||A||A|
|Risk of inadequate performance due to reduced muscle mass, strength and endurance||C||A||A||U|
|Risk of renal stone formation||C||C||C||C|
|Risk of bone fracture||C||A||C||A|
|Risk of intervertebral disc damage||I||I||I||I|
|Risk of cardiac rhythm problems||A||C||I||I|
|Risk of reduced physical performance capabilities due to reduced aerobic capacity||C||C||A||U|
|Risk of crew adverse health event due to altered immune response||C||A||A||A|
|Risk of impaired control of spacecraft, associated systems and immediate vehicle egress due to vestibular/sensorimotor alterations associated with spaceflight||C||C||C||A|
|Risk of clinically relevant unpredicted effects of medication||C||C||C||U|
|Risk of spaceflight-induced intracranial hypertension/vision alterations||U||I||U||U|
|Risk of decompression sickness||C||C||C||C|
|Risk of injury from dynamic loads||C||A||A||I|
|Risk of performance decrement and crew illness due to an inadequate food system||C||C||A||U|
|Risk of inadequate human-computer interaction||C||C||C||C|
|HRP Research Rating|
|Risk of performance errors due to training deficiencies||C||C||C||A|
|Risk of inadequate design of human and automation/robotic integration||C||C||C||A|
|Risk of inadequate critical task design||C||C||C||C|
|Risk of adverse health effects of exposure to dust and volatiles during exploration of celestial bodies||N/A||A||I||I|
|Risk of incompatible vehicle/habitat design||C||C||C||A|
|Risk of adverse health effects due to alterations in host-microorganism interactions||C||C||A||A|
|Risk of unacceptable health and mission outcomes due to limitations of inflight medical capabilities||C||A||A||U|
|Risk of adverse behavioral conditions and psychiatric disorders||C||C||A||U|
|Risk of performance errors due to fatigue resulting from sleep loss, circadian desynchronization, extended wakefulness, and work overload||C||C||C||C|
|Risk of performance decrements due to inadequate cooperation, coordination, communication, and psychosocial adaptation within a team||A||C||A||A|
|Risk of radiation carcinogenesis||C||A||U||U|
|Risk of acute radiation syndromes due to solar particle events||C||C||C||C|
|Risk of acute or late central nervous system effects from radiation exposure||A||A||I||I|
|Risk of degenerative tissue or other health effects from radiation exposure||A||A||I||I|
NOTES: A = Acceptable; C = Controlled; EVA = extravehicular activity; HRP = Human Research Program; I = Insufficient Data; ISS = International Space Station; N/A = not applicable; NEA = near-Earth asteroid; U = Unacceptable.
The research rating categories (full definitions in NASA, 2013c) focus on the extent to which there is evidence that the projected plans for that design reference mission will meet existing standards for maintaining crew health and performance or that countermeasures exist to control the risk.
SOURCE: NASA, 2013c.
The use of health standards to protect individuals engaged in specific types of work or activities is not unique to space exploration or exploratory activities. A standard is a requirement, norm, or convention that applies to performing an activity or to the properties of a product or thing. Governments have long applied health standards to protect the welfare of workers (see Chapter 4). In occupational settings, health standards guide design, research, and engineering activities and commonly serve the following core functions:
- Worker Protection: Health standards, often in the form of permissible exposure limits or performance standards, limit the duration and/or level of exposure to hazardous substances or set the health or performance levels that workers need to maintain. For example, OSHA issues permissible exposure limits that set regulatory limits on hazardous exposures for a wide range of workplaces and industries (OSHA, 2013).
- Stimulation of Design and Innovation: Health standards establish the specifications toward which engineers, researchers, and others strive in their design and innovation. In the hierarchy of worker protection controls against occupational hazards, the preferred solution is to eliminate the hazard. However, if that is not possible, then an engineering, design, or other solution is sought that can be built into the work environment and, therefore, does not require individuals behaviors. For example, individuals would need to remember to arrange work schedules to limit the time a worker is exposed (an example of an administrative control) or to put on gloves or respiratory protection (examples of personal protective equipment controls). Standards provide the goals for engineering or operational solutions during the design and development of the mission. Standards also provide guidance on flight rules for implementation during the mission.
- Level the Playing Field: Health standards can also be used as transparent criteria for specific jobs, so that prospective workers and employers have a clear understanding of the job requirements. In this respect, standards are instrumental in ensuring that everyone knows from the outset the criteria for the position and all meet the requirements. Criteria for applying to the astronaut corps are discussed later in this chapter.
- Engendering Confidence in, and Legitimacy for, Institutions: Standards also play a role in stabilizing collaborative human activities. For instance, space exploration requires large outlays of material and infrastructural support, much of which derives from federal funding. As astronauts are not conscripted, it also requires the voluntarism of individuals who join the astronaut corps and agree to participate in spaceflight missions. Stewardship of this support depends in part on ensuring that the institutions are acting prudently, competently, and showing due regard for those who enter into the collaboration.
Health Standards for Spaceflight
In its efforts to protect the health and safety of spaceflight crew members, NASA has developed spaceflight human system standards (termed in this report as “health standards”), as delineated in Boxes 2-1 and 2-2, that aim to provide a “healthy and safe environment for crew members, and to provide health and medical programs for crew members during all phases of space flight” (NASA, 2007, p. 8). These standards include consideration of preflight, inflight, and postflight health issues and comprise two volumes: Volume 1: Crew Health and Volume 2: Human Factors, Habitability, and Environmental Health (NASA, 2007, 2011b) (see Boxes 2-1 and 2-2).1 NASA’s health standards fall into three categories:
(1) Fitness-for-duty standards—These standards provide a “minimum measurable capability or capacity” for the specific parameter (e.g., aerobic capacity) based in some cases on normative values for age and sex for the general population (NASA, 2007, p. 17).
(2) Space permissible exposure limits—These types of standards set ceilings on risk exposures during missions and are based on measures of exposure to a physical or chemical agent (e.g., radiation) with quantifiable limits over a given amount of time (e.g., lifetime radiation exposure).
1NASA’s health standards are complemented by NASA standards for engineering and for safety and mission assurance with documentation, including the Human Integration Design Handbook, NASA Spacecraft Maximum Allowable Concentration Tables, and NASA Spacecraft Water Exposure Guidelines (NASA, 2008b,c, 2010, 2012b).
(3) Permissible outcome limits—These standards reference the assessment of a biological or clinical parameter with the standard outlining the acceptable maximum decrease or change (e.g., bone density) (NASA, 2007).
The standards may be cited in NASA contract, program, and other documents as technical requirements; “mandatory requirements are indicated by the word ‘shall,’ statement of fact and descriptive material by ‘is,’ and permission by ‘may’ or ‘can.’ Tailoring of, deviation from, or waivers to this standard for application to a specific program or project shall be approved by the NASA Chief Health and Medical Officer” (NASA, 2007, p. 9).
NASA develops the standards to cover the broad range of space missions. The agency also develops more detailed documents for each spaceflight, including the Crew Health Concept of Operations document and the Medical Operations Requirements document (NASA, 2007).
NASA Health Standards: Crew Health (2007)
1. Fitness-for-Duty Aerobic Capacity Standard
a. Crew members shall have a pre-flight maximum aerobic capacity (VO2max) at or above the mean for their age and sex (see American College of Sports Medicine Guidelines below in Table A).
b. The in-flight aerobic fitness shall be maintained, either through countermeasures or work performance, at or above 75 percent of the pre-flight value, as determined by either direct or indirect measures.
c. The post-flight rehabilitation shall be aimed at achieving a VO2max at or above the mean for age and sex (see Table A).
TABLE A 50th Percentile Values for
Maximal Aerobic Power (ml kg-1 min-1)
2. Fitness-for-Duty Sensorimotor Standard
a. Pre-flight sensorimotor functioning shall be within normal values for age and sex of the astronaut population.
b. In-flight fitness-for-duty standards shall be guided by the nature of mission-associated high-risk activities, and shall be assessed using metrics that are task specific.
c. Sensorimotor performance limits for each metric shall be operationally defined.
d. Countermeasures shall maintain function within performance limits.
e. Post-flight rehabilitation shall be aimed at returning to baseline sensorimotor function.
3. Fitness-for-Duty Behavioral Health and Cognition Standard
a. Pre-flight, in-flight, and post-flight crew behavioral health and crew member cognitive state shall be within clinically accepted values as judged by clinical psychological evaluation.
b. End-of-mission rehabilitation for crew member cognitive state shall be aimed at transitioning the crew member back to pre-flight values. c. End-of-mission rehabilitation for behavioral health of the crew member shall be aimed at transitioning the crew member back into terrestrial work, family, and society.
d. The planned number of hours for completion of critical tasks and events, workday, and planned sleep period shall have established limits to assure continued crew health and safety.
4. Fitness-for-Duty Hematology and Immunology Standard
a. Pre-launch hematological/immunological function shall be within normative ranges established for the healthy general population.
b. In-flight countermeasures shall be in place to sustain hematological/ immunological parameters within the normal range as determined by direct or indirect means.
c. Countermeasures and monitoring shall be developed to ensure immune and hematology values remain outside the “critical values” (i.e., that level which represents a significant failure of the hematological/immunological system and is associated with specific clinical morbidity) defined for specific parameters.
d. Post-flight rehabilitation shall be aimed at returning to pre-flight baseline.
5. Permissible Outcome Limit for Nutrition Standard
a. Pre-flight nutritional status shall be assessed and any deficiencies mitigated prior to launch.
b. In-flight nutrient intake shall be no less than 90 percent of the calculated nutrient requirements, based on an individual’s age, sex, body mass (kg), height (m), and an activity factor of 1.25.
c. Nutrient planning shall be aimed at maintaining a body mass and composition greater than 90 percent of pre-flight values.
d. Post-flight nutritional assessment and rehabilitation shall be aimed at returning to baseline.
6. Permissible Outcome Limit for Muscle Strength Standard
a. Pre-flight muscle strength and function shall be within normal values for age and sex of the astronaut population.
b. Countermeasures shall maintain in-flight skeletal muscle strength at or above 80 percent of baseline values.
c. Post-flight rehabilitation shall be aimed at returning to baseline muscle strength.
7. Permissible Outcome Limit for Microgravity-Induced Bone Mineral Loss Performance Standard (Baseline with Measured T-Score)
a. Crew members’ pre-flight bone mass Dual Energy X-ray Absorptiometry (DEXA T) score shall not exceed -1.0 (-1.0 Standard Deviation [SD] below the mean Bone Mineral Density).
b. Countermeasures shall be aimed at maintaining bone mass in-flight consistent with outcome limits.
c. The post-flight (end of mission) bone mass DEXA T score shall not exceed -2.0 (-2.0 SD below the mean Bone Mineral Density).
d. Post-flight rehabilitation shall be aimed at returning bone mass to pre-flight baseline.
8. Space Permissible Exposure Limit for Space Flight Radiation Exposure Standard
a. Planned career exposure for radiation shall not exceed 3 percent risk of exposure-induced death (REID) for fatal cancer.
b. NASA shall assure that this risk limit is not exceeded at a 95 percent confidence level using a statistical assessment of the uncertainties in the risk projection calculations to limit the cumulative effective dose (in units of Sievert) received by an astronaut throughout his or her career.
c. Exploration Class Mission radiation exposure limits shall be defined by NASA based on National Council on Radiation Protection (NCRP) recommendations.
d. Planned radiation dose shall not exceed short-term limits as defined in Table B.
e. In-flight radiation exposures shall be maintained using the as low as reasonably achievable (ALARA) principle.
TABLE B from Appendix F Dose limits for short-term or career non-cancer effects (in mGy-Eq or mGy). Note RBE’s for specific risks are distinct as described below.
NOTES: BFO = blood-forming organ; CNS = central nervous system; RBE = relative biological effectiveness. Supporting information and rationale for each of the standards is found in Appendix F, Rationale for Space Flight Health Standards for Human Performance, of NASA-STD-3001 (NASA, 2007).
*Lens limits are intended to prevent early (<5 yr) severe cataracts (e.g., from a solar particle event). An additional cataract risk exists at lower doses from cosmic rays for sub-clinical cataracts, which may
progress to severe types after long latency (>5 yr) and are not preventable by existing mitigation measures; however, they are deemed an acceptable risk to the program.
**Heart doses calculated as average over heart muscle and adjacent arteries.
***CNS limits should be calculated at the hippocampus.
SOURCE: NASA, 2007.
Examples of NASA Health Standards on
Human Factors, Habitability, and Environmental Health (2011)
• Physical Characteristics and Capabilities
o Aerobic Capacity (4.9): An individual’s absolute aerobic capacity determines the ability to perform a task at a given level of work. The system shall be designed to be operable by crew members with the aerobic capacity as defined in NASA-STD-3001, Volume 1.
• Perception and Cognition
o Situational Awareness (SA) (5.2.2): SA refers to the process and outcome of understanding the current context and environment, evaluating that situation with respect to current goals, and projecting how that situation will evolve in the future. Systems shall be designed such that the SA necessary for efficient and effective task performance is provided and can be maintained for all levels of crew capability and all levels of task demands.
• Natural and Induced Environments
o Atmospheric Data Recording (188.8.131.52): For each isolatable, habitable compartment, the system shall automatically record pressure, humidity, temperature, ppO2, and ppCO2 data.
• Habitability Functions
o Orthostatic Intolerance Countermeasures (7.4.5): The system shall provide countermeasures to mitigate the effects of orthostatic intolerance when transitioning from microgravity to gravity environments.
o Consistent Orientation (184.108.40.206): In microgravity, the system shall establish a local vertical orientation.
• Crew Interfaces
o Private Audio Communication (10.5.3.9): The system shall provide the capability for private audio communication with the ground.
o Suit Equilibrium Pressure (220.127.116.11): Suits shall maintain pressure within 0.1 psi (0.689 kPa) after the suit has achieved an equilibrium pressure for a set-point.
SOURCE: NASA, 2011b.
Developing and Updating NASA’s Health Standards
NASA’s health standards are established and maintained by NASA’s Office of the Chief Health and Medical Officer (OCHMO) who reports to the NASA Administrator (NASA, 2013d). The mandate for these standards is delineated in NASA Policy Directive 8900.5, which specifies that NASA’s policy is to “provide a healthy and safe environment for crewmembers to enable successful human space exploration” with the OCHMO responsible for establishing and maintaining spaceflight health and medical standards (NASA, 2011a, p. 1). The standards follow an occupational health model that sets hazardous exposure limits and delineates health criteria for workers.
Requests for new or revised health standards are submitted to the OCHMO which decides whether or not a standards development team will be assembled. Any office within NASA, including the Astronaut Office,2 may initiate a request. Standards development teams include internal NASA experts, and external experts can be appointed (NASA, 2012a). If the OCHMO decides that the revision of an existing standard or the development of a new standard should be explored, the standards development team first conducts a comprehensive review of the available scientific and clinical evidence, as well as operational data and experience from Apollo, Skylab, Shuttle, Shuttle-Mir, and ISS missions. The team then prepares a draft (or revised) standard that is reviewed by the Chief Health and Medical Officer who decides whether to convene an external technical review (NASA, 2007, 2012a). After these reviews are completed, the revised or new standard is presented to the NASA Medical Policy Board, which decides whether to recommend the standard to the Chief Health and Medical Officer, who is responsible for final approval (NASA, 2012a; Liskowsky, 2013). A 2007 IOM report commissioned by NASA assessed the health standards development process and outlined a set of principles for standard-setting, specifying that they should be evidence-based, open and transparent, well documented, well informed, and dynamic (IOM, 2007).
As with all NASA standards, reviews of the health standards are conducted every 5 years (NASA, 2012a). Reviews of the health stand
2Comprised of the members of the Astronaut Corps (astronauts selected and trained to fly as crew members) as well as administrative and engineering support staff, the Astronaut Office provides support for safety reviews, engineering tests, program development, public and educational outreach, and government and external collaborations (NRC, 2011). The Chief of the Astronaut Office reports to the Director of Flight Crew Operations.
ards can also be conducted at any time that new research data or information from clinical observations indicate that an update review is needed (NASA, 2012a). Inputs into NASA’s review decision often include studies from external organizations, including the National Research Council Committee on Toxicology’s review of exposure guidelines for selected airborne contaminants and the IOM’s reviews of the Human Research Program’s evidence reports (e.g., NRC, 2008; IOM, 2014). NASA’s Human System Risk Board also monitors the status of each of the health risks.
NASA’s health standards apply to all NASA human spaceflight programs including long duration and exploration missions (NASA, 2007). NASA standards “address those areas where the human system has shown particular vulnerability in response to adaptation or exposure to microgravity” (NASA, 2007, p. 10). The ethics challenges that result from having one set of space health standards across a wide swath of mission types are considered later in this report (see Chapters 5 and 6). As noted in the 2007 IOM report, “The challenge in developing space flight health standards is to determine an acceptable level of risk that provides maximum feasible protection of crew health and safety without jeopardizing mission success or ‘overengineering’ either the technical or medical solutions that mitigate these risks. This challenge becomes more daunting as missions become more complex, involving new vehicles, longer durations, greater distances from Earth, and novel environments” (IOM, 2007, p. 5). The report noted the paucity of data for many of the health risks and highlighted the challenges posed by the need to conduct quantitative risk assessments, limited data regarding some health issues or hazardous exposures, and the small number of individuals who have experienced spaceflight, particularly regarding certain exposures (IOM, 2007).
NASA Crew Selection and Medical Certification Standards
In addition to spaceflight health standards, NASA has developed standards that specify health-related criteria for astronaut selection and parameters for health and medical screening, evaluation, and certification including annual certification medical examinations (NASA, 2012a). Applicants to NASA’s Astronaut Candidate Program, in addition to meeting specified academic and citizenship requirements, must complete long duration spaceflight physicals with requirements to meet a number of criteria, including distance and near visual acuity correctable to 20/20 in each eye (refractive surgical procedures of the eye are allowed,
“providing at least 1 year has passed since the date of the procedure with no permanent adverse after effects”), blood pressure below 140/90 in a sitting position, and specific height requirements (NASA, 2013a).
Once in the program, astronauts have annual medical examinations and screenings. As needed, waivers on the medical criteria for annual certification are considered by the NASA Aerospace Medicine Board on a case-by-case basis to determine if an astronaut who develops a health condition can continue to work (NASA, 2009a). Waivers are used to address issues specific to an individual astronaut’s risk profile but are not designed for situations where the mission risk fails to meet accepted parameters.
SUMMARY AND RECOMMENDATION
NASA has detailed risk management processes applicable to its efforts in engineering, safety, and health. The starting point in decisions about whether to allow levels of risks that would be in excess of NASA’s health standards is determining that the current health standards reflect the most relevant and up-to-date evidence about spaceflight-related risks to human health and safety. The committee believes it is important for NASA to articulate the criteria for evaluating new evidence and explicitly outline the processes it uses to ensure that evaluation, implementation, and potential revision of health standards are fully consistent with the set of ethics principles outlined in this report. Current NASA policy does specify the administrative processes and levels of approval for the initiation of a new health standard or a revision to a current health standard. Health standards are reviewed every 5 years or reviews can be triggered at any time if new research data or information from clinical observations indicate an update review is needed. However, the committee believes additional information about decision criteria, process, and application of ethics principles should be available to the public.
Recommendation 1: Expand on the Policies for Initiating and Revising Health Standards
NASA should ensure that its policies regarding health standards detail the conditions or circumstances (and relevant priorities) that initiate development or revision of health standards and explicitly indicate how these policies are fully consistent with the set of ethics principles outlined in this report.
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