UV in Interior Lighting of Spaceships Can Lead to Infectious
by Duane Dunkerson
Immune suppression has been observed to occur in astronauts.
It has been attributed previously to microgravity or stress.
Speculation on a Role for Photoimmunosuppression During Space
Missions by Daniel H. Hug, John K. Hunter, and Duane D. Dunkerson.
Immunity suppression can weaken an astronaut's state of health
so that infections can start or can be worsened. This article
proposes that one possible component of immune suppression has
not been taken into account. UV radiation from spacecraft interior
lighting and special spacecraft plant growth lamps contain a range
of UV wavelengths that may lead to immune suppression. This immune
suppression, called photoimmune suppression, was discovered in
mice around 1976.
The importance of consideration being given to UV sources inside
spacecraft increases as the duration of the flight lengthens.
Space missions of days, weeks and months have or will be conducted.
Under consideration now are possible manned missions to Mars.
Proposals for growing the astronauts' food while enroute have
been put forth.
The aftereffects of a short exposure to the harmful UV can last
for weeks. It is possible that UV exposure before launch while
engaging in various outdoor activities, can be affecting the astronauts
long after a mission commences.
Urocanic acid (UCA), a molecule found in the skin and elsewhere,
has been implicated as a photoreceptor for the harmful UV. Once
the UCA absorbs the UV, then thereafter, in an unknown manner,
immune suppression can occur. If one has more UCA, the amount
of immune suppression can be increased.
Human beings in space have an increased immune suppression as
compared to their terrestrial levels of immunity. Space motion
sickness, weight loss, muscle wasting, and protein catabolism
( protein destruction) afflict astronauts. Protein malnutrition
can arise from the specific responses to motion sickness. The
protein catabolism occurring in astronauts is characterized by
a lessening in the amount of methionine found in the astronauts'
plasma. Methionine is a molecule used for the making of proteins
in the body. Less methionine means more UCA. This increased UCA
could find its way to the skin of the astronauts. There the UCA
could absorb the UV from interior lighting or plant growth lamps
that could adversely affect the health of spacecraft occupants.
Astronauts float about all parts of their living quarters. Illumination
lamps may be inches from them. The astronauts often function in
a "shirtsleeves" environment that has them in T-shirts
and shorts. Acrylic diffusers on the light source are of benefit.
Grid diffusers pass the harmful UV. Filtered light from the exterior
of the spacecraft via portholes and filtered light from the interior
are presumed safe but filters weaken with age.
Little consideration has been given in all sectors of the workplace
and home in regard to the harmful effects of the prevalent fluorescent
lighting's UV found in the office, the production area, and in
the domestic settings. Such scant attention to earthbound light
sources may be repeated in orbital and deep space activities.
To counter bone loss in astronauts and bacterial growth in the
spacecraft, and to promote vitamin formation, it has been proposed
to use UV radiation. Also, plant growth in spacecraft has been
planned for to provide oxygen and food. These plant growth lamps
and radiation to promote the health of the astronauts could represent
a danger for the astronauts.
It is hazardous duty to be in illuminated floating and restricted
quarters for lengthy periods of time. It would seem there might
not be friendly confines for space travel until the size of the
craft increases beyond the dimensions of glorified broom closets.