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GLOSSARY
Actinic or solar degeneration: A complex of degenerative
changes in skin caused by chronic exposure to sunlight.
The skin appears thick and furrowed but may also have
zones of thinned epidermis.
Action spectrum: A graph or mathematical expression
indicating the relative effectiveness of radiation at
different wavelengths for producing a photochemical or
photobiological effect.
Antigen: Any substance that, when introduced into,the
body, stimulates the production of an antibody, a
protein that acts to neutralize the antigen and thus
produce immunity.
Backscatter ultraviolet (B W): Solar radiation in the
ultraviolet region that is scattered from the
atmosphere back into space.
Basal cell skin cancer: A relatively common type of skin
cancer that can result from exposure to sunlight. Its
tendency to metastasize is small. This cancer arises
in the basal cell layer of the epidermis where cells
continually divide and replace dead cells in the
epidermis.
Carcinogenesis: The production and development of
cancer. The process of carcinogenesis may be divided
into at least two parts. The first part, initiation,
involves the interaction of a physical or chemical
carcinogen with cells, resulting in altered cells that
are potentially cancerous, or precancerous. Such an
altered cell may remain quiescent for a long time
before subsequent cell proliferation and the
expression of a tumor. The second part, promotion,
involves the subsequent proliferation of the altered
cells. Substances called promoters, administered
after, even long after, the initiating event, may
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result in observed tumors. But, if administered
before the initiating event, promoters will not
enhance the observed carcinogenic effects of
initiators. Initiators are thought to act via
reactions with cellular macromolecules--in many
instances DNA. The molecular mechanisms of promotion
are not well understood, but are hypothesized to
affect the regulatory activities of cells or cell-cell
interactions (Berenblum and Armuth 1981).
Catalysis: A means by which the rate of a chemical
reaction is enhanced through the action of a catalyst
(a substance that itself remains chemically unaltered).
Catalytic cycle: A set of chemical reactions wherein one
or more reactive species are alternately consumed and
generated. The net effect is to cause a reaction
between the partners of the reactive species to yield
the products. The simplest example of a catalytic
cycle involving ozone is
O3 + NO + NO2 ~ O2
O + NO2 ~ NO + O2
O3 + 0 ~ O2 + O2 (net).
_
In these reactions the molecules NO and NO2 act as
catalysts for the combination of O-atoms with O3 to
produce O2. The direct reaction can occur, but the
presence of NO and NO2 (causing the same net change)
increases the rate by means of the two-reaction
pathway.
~.
Chlorocarbon: A hydrocarbon in which one or more
chlorine atoms are substituted for hydrogen atoms.
Chlorofluorocarbon: A hydrocarbon containing chlorine
and fluorine as substituents for hydrogen atoms.
Chlorofluoromethane: A methane derivative containing
chlorine and fluorine as substituents.
Chromatin: A complex of highly polymerized DNA with
basic proteins (histone or protamine) that stains
intensely with basic dyes; regarded as the physical
carrier of genes.
Chromophores: Molecules or parts of molecules that
absorb light.
Cohort: A group born in a specific time interval, e.g.,
one calendar year.
Cohort analysis: The study of a cohort from its
inception to its final dissolution, e.g., a study of
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all the people born in one calendar year followed
until the last person dies.
Contact hypersensitivity: An immune system response at
the cellular level to an antigen applied to the skin,
to which the animal has been previously sensitized.
The response is specific to the antigen due to
specific cell-surface antigen receptors.
Core regions of chromatin: Mammalian DNA may be
visualized as a strand with aggregates of protein
occurring at intervals along the strand. The protein
aggregates are called nucleosomes, and are known as
core regions, and the intervening areas are the linker
regions .
Cross-sectional analysis: A type of empirical analysis,
i.e., analysis concerned with the establishment of
quantitative or qualitative relations between
observable variables, using cross-section data.
Cross-section data are observations on variables at a
point in time, as opposed to time-series data.
Dermis: A 1-mm to 4-mm layer of primarily collagenous
connective tissue that provides much of the structural
integrity of the skin. It is located beneath the
epidermis.
Ecosystem: A dynamic, integrated assemblage of plants,
animals, and microorganisms that is definable by the
interactions among the living and nonliving components
of the functional unit.
Eddy diffusion: A process whereby, through the action of
random eddies in a turbulent fluid, heat and/or matter
is transported along a gradient.
Epidermis: The outermost layer of the skin,
approximately 100 am thick, separated from the next
layer (dermis) by a basement membrane. The epidermis
consists of five layers: (1) the outermost protective
stratum corneum (no nuclei); (2) several layers of
transparent nucleated cells; t3) the granular layer,
(4) the Malpighian layer, consisting of multiple
squamous or prickle cells; and (5) the basal layer,
composed of germinative cells. Less than 10 percent
of incident W-B may pass through the epidermis.
Erythema: A reddening of the skin due to a dilation of
the blood capillaries. It is one of the components of
the syndrome commonly known as sunburn.
Excision repair: A cellular repair mechanism that
eliminates photoproducts in DNA, thereby ameliorating
UV damage to DNA. In this process, products of UV
irradiation are removed from one strand of a DNA
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double helix by specific enzymes that work in the
dark. The opposite unaltered strand is then used as a
template on which a new complementary strand is built.
Fibroblast: A connective tissue cell, flat and
elongated. It performs the function of supporting and
binding tissues of all sorts in higher organisms.
Freon: The U.S. trade name for several
chlorofluorocarbons.
Fell, F-12: The halocarbon Fell is trichloro-
fluoromethane CFC13 and F-12 is dichlorodi-
fluoromethane CF2C12. These are the two most-used
chlorofluorocarbons and they constitute most of the
threat to ozone by this class of compounds.
Halocarbon: A hydrocarbon in which one or more halogen
atoms are substituted for hydrogen atoms.
Heterochromatic light or radiation: Light or radiation
consisting of a range of (more than a single)
wavelengths. See also monochromatic light or
radiation.
Hydrocarbon: A compound of hydrogen and carbon.
Immunosuppression: The suppression of a natural immune
response of an organism to a foreign agent.
Initiator. See carcinogenesis.
Langerhans cells: In the skin, dendritic cells in the
epidermis that function as part of the immune system.
Lentigo malignant melanoma: A subtype of melanoma
occurring almost exclusively on the exposed parts of
the face, neck, and hands; characterized by the
presence of brownish pigmented spots on the skin
(lentigines or freckles) that increase in size and
darken in color. The spots are predominantly flat, 2
cm to 20 cm in diameter with irregular borders and
pigment pattern. Raised areas indicate invasive tumor.
Linker regions of chromatic: See core regions of
chromatic.
Lymphocytes: Circulating white blood cells that are part
of the immune system.
Mast cell: A connective tissue cell whose physiologic
function remains partly unknown; after a variety of
insults or stimuli the cell releases chemicals that
are mediators of inflammation.
Melanin: A dark pigment found in skin (epidermis), hair,
and various tumors. The epidermal melanin unit is
composed of melanocytes and associated Malpighian
cells. See also epidermis, melanocytes.
Melanocytes: Cells located in the basal layer of the
epidermis with dendritic (armlike) projections that
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extend into the Malpighian layer of the epidermis.
These cells form the pigment melanin, which they pass
into the Malpighian cells.
Melanoma: A tumor made up of melanin-pigmented cells.
Melanoma is a serious, sometimes fatal form of skin
cancer, usually developing from a nevus and consisting
of black masses of cells with a tendency to
metastasize.
Mixing ratio:
The ratio of the concentration of a
gaseous species to the total concentration of the gas.
Model: In the context of Part I of this report a model
is a mathematical representation of the transport and
chemical behavior of species in the atmosphere. In
principle, with suitable specification of initial and
boundary conditions, the distributions of any and all
(relevant) chemical species in space and time can be
computed by means of the model.
Monochromatic light or radiation: Light or radiation
consisting of a single wavelength. See also
heterochromatic light or radiation.
Nevus: Any congenital growth or mark on the skin, such
as a birthmark.
Odd-hydrogen compound: Specifically one of the radical
species OH (hydroxyl) and HO2 (hydroperoxyl) that
contain a single H-atom each. The term odd-hydrogen
is used more in analogy with odd-nitrogen and odd
oxygen (see below).
Odd-nitrogen compound: One of the species containing a
single nitrogen atom such as NO, NO2, HNO3,
ClONO 2, MONO, and HOONO 2 .
Odd-oxygen species: Specifically O-atoms and O3 (as
opposed to the "even oxygen" species O2). Since
O-atoms are rapidly converted mainly to O3,
reactions which remove them are considered as
effectively removing O3. The set of reactions that
remove both odd-oxygen species thus constitutes the
means by which ozone abundance becomes reduced.
Ozone (O3): An allotrope of oxygen containing three
atoms. It is a reactive, toxic, acrid smelling,
colorless gas under atmospheric conditions. It is
created naturally in the stratosphere where its
abundance is the largest and where it exists as a
permanent layer. Ozone is created in the troposphere
by the so-called smog reactions involving the oxides
of nitrogen and hydrocarbons.
Ozonesonde: (a) One of several devices that are carried
aloft through the atmosphere by balloons to measure
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the vertical concentration distribution of ozone. (b)
The plotted record of the vertical concentration
distribution of ozone obtained by such a device.
Photochemical reaction: Any reaction in which one or
more of the reactants or their reactive precursors are
created by the interaction of light with a molecule or
atom. Generally the term refers to free radical
reactions wherein the radicals or their radical
precursors were created by photolysis of a stable
molecule.
Photobiology: That branch of biology that deals with the
effects of light on living organisms.
Photochemistry: That branch of chemistry that deals with
the chemical effects of light.
Photoimmunology: That branch of immunology that deals
with the effects of light on the immune system. Most
of what is now known about the effects of W on the
immune systems of animals and humans has been learned
within the past five years.
Photokeratitis: An acute, painful irritation of the
cornea of the eye caused by exposure to UV-B or WV-C.
Photon: A "particle" of light. A photon is the smallest
unit (quantum) of light that exists; its energy
depends on the wavelength of the light.
Photoproducts:
Specific changes in molecular structure
that result from the absorption by molecules of
photons (in this report, photons in the W band
specifically).
Photoprotection: A protective cellular mechanism whereby
a preceding illumination with W-A may decrease the
damage to DNA caused by UV-B. Photoprotection
involves the induction by W-A of a delay in growth,
allowing for more time after UV-B irradiation is
completed for error-free dark-repair systems to repair
the damaged DNA.
Photoreactivation: A cellular repair mechanism that
eliminates photoproducts in DNA, thereby ameliorating
UV damage to DNA. In this process, an enzyme binds to
a DNA molecule containing pyrimidine dimers. The
complex of enzyme and damaged DNA can absorb W-A or
visible light, which causes the dimer to split,
thereby repairing the damage.
Planetary waves: Longitudinally ranging motions of the
atmosphere organized on a scale of the magnitude of
the distance around the earth.
Promoter: See carcinogenesis.
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Pyrimidine dimers: Biologically damaging products of UV
irradiation, formed when two adjacent pyrimidine
residues within one DNA strand bond to each other.
Radical (also called free radical): Any chemical species
(atom or molecule or ion) that contains one or more
unpaired electrons. In this report the term refers to
reactive species such as OH, HO2, C1, and C1O, each
of which contains a single unpaired electron. The
ease of combining with other molecules to form bonds
having paired electron spins is understood as the seat
of their reactivity.
Rate-limiting reaction (or process): In a sequence of
reactions, that reaction which is the slowest and thus
limits the rate at which the initial reactants
ultimately become converted to products.
Robertson-Berger (R-B) meter: A meter that records,
after each 30-minute interval, a measure of the
cumulative amount of UV that passes through its
filters and is absorbed by its photosensors.
Half-hourly recordings may range from 0 to slightly
over 1000 depending on geographical location and
prevailing meteorological conditions. The meters are
designed to measure UV effective in producing skin
erythema (sunburn), but in fact measure some longer UV
wavelengths as well (see Figure 2.2). A count of
about 400 in a half hour is estimated to produce skin
erythema on the typical Caucasian skin.
Solar backscatter UV (SB W):
See backscatter ultraviolet.
Solar degeneration: See actinic or solar degeneration.
Spectrophotometer: An electro-optical device that
measures the intensity of light distributed over a
spectral range (of wavelength or frequency). The
Dobson meter is an example of a specialized
spectrophotometer that measures and intercompares the
relative intensities of sunlight at four different
wavelengths, two of which correspond to absorption
peaks in the ozone spectrum. From this measurement,
the column abundance of ozone can be calculated.
Squamous cell skin cancer:
A relatively common type of
skin cancer that can result from exposure to
sunlight. Its tendency to metastasize is small. This
cancer arises in the Malpighian layer of the epidermis
Stratosphere: The region of the atmosphere above the
tropopause (altitude range 6 km to 17 km) and below
the stratopause (altitude about 55 km). The principal
characterizing feature of the stratosphere is its
.
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thermal stability. That is, the temperature increases
with increasing height in the stratosphere.
Stratum corneum: A low m layer of dead cells, protein,
and other molecules on the outermost surface of the
epidermis. W-B is strongly absorbed by the stratum
corneum.
T suppressor cells:
suppresses cellular immune response.
Transformation (in vitro): An inheritable change wherein
cells in culture are altered such that they do not
stop growing when they encounter similar cells.
Colonies of UV-transformed rodent cells are often
tumorigenic when injected into certain animals, but no
tumorigenicity has been shown for the W-transformed
human cells described in the experimental results
shown in Figure 3.1.
Tropopause: The surface that is the boundary between
the troposphere and the stratosphere. The height of
this surface varies in the range 6 km to 17 km
depending upon latitude and season.
Troposphere: The main layer of the atmosphere between
the surface and the tropopause.
Ultraviolet radiation (W): Light in the range of
wavelengths less than 400 nm. The lower limit is a
matter of definition to distinguish between W and
x-rays at even shorter wavelengths.
Ultraviolet radiation in the wavelength region
from 320 nm to 400 nm; near- W .
UV-B: Ultraviolet radiation in the wavelength region
from 290 nm to 320 nm; mid-UV.
WV-C: Ultraviolet radiation in the wavelength region
from 190 nm to 290 nm; far- W.
Umkehr method: A mathematical manipulation of the data
from the Dobson spectrophotometer that creates a rough
representation of the vertical profile of ozone. The
data come from measurements of the zenith sky as the
A certain class of lymphocytes that
WV-A:
sun rises or sets.
Xeroderma pigmentosum: A genetically inherited,
sunlight-sensitive, cancer-prone disease; rare and
often fatal if the individuals are not protected from
sun exposure; characterized by brown spots and ulcers
of the skin. Cells from individuals with this disease
are almost always defective in DNA repair, and the
high prevalence of skin cancer in such individuals is
ascribed to this defect.
Representative terms from entire chapter:
skin cancer
