1. Lecture class:
The hygienic aspects of solar radiation and its
artificial analogues.
Name of the discipline: Hygiene
for the specialty 31.05.01 General Medicine for the training
of foreign students
Division: Department of Hygiene
Speaker: Assistant of the Department of Hygiene
Olga Yurievna Yamilova
3. Ultraviolet radiation is a type of non-ionizing
radiation of the electromagnetic spectrum and is in the
wavelength range from 100 nm up to 400 nm.
The short-wave limit of the UV range is often
considered as the boundary between the spectrum of
ionizing radiation (wavelength <100 nm) and the
spectrum of non-ionizing radiation.
The UV region can be roughly divided into the UV-
A (315-400 nm), UV-B (280-315 nm), and UV-C (100-
280 nm) ranges, although there are other definitions
for the boundaries of the UV-A, UV-B, and UV-C ranges.
4. Most artificial sources of UV radiation, with
the exception of lasers, emit a continuous spectrum
in the UV range, containing characteristic peaks,
depressions, and lines.
These sources include various lamps used in:
– medicine,
– industry,
– commerce,
– scientific research.
5. Artificial UVR sources are widely used in industry and,
because of the germicidal properties of certain portions of the
UVR spectrum, they are also used in hospitals, biological
laboratories, and schools.
UVR is extensively used for therapeutic purposes, as in
the prevention of vitamin D deficiency, the treatment of skin
diseases, and for cosmetic purposes. Artificial UVR sources are
available as consumer products.
6. UVR can be classified into regions:
– UV-A,
–UV-B,
–UV-C.
7. UV-C
(200-200 nm)
Wavelengths in the UV-C region cause unpleasant, but usually
not serious effects on the skin and eye.
Although UV-C is very efficiently absorbed by nucleic acids, the
overlying dead layers of skin absorb the radiation to such a
degree that there is only mild erythema and, usually, no late
sequelae, even after repeated exposures.
Since solar UVR below 290 nm is effectively absorbed by
stratospheric ozone, no such radiation reaches living
organisms from natural sources.
8. UV-B
(280-320 nm)
Most observed biological effects of UV-B radiation are extremely
detrimental to living organisms.
However, living organisms are usually protected from excessive
solar UV-B radiation by feathers, fur, or pigments that absorb the
radiation before it reaches sensitive physiological targets.
Other means of protection include behavioural patterns and the
ability to tolerate certain UV-B radiation injury because of
molecular and other repair mechanisms.
9. UV-A
(320-400 nm)
Much less is known about the biological effects of UV-A
radiation.
It can augment the biological effects of UV-B, and doses of UV-A,
which, alone, do not show any biological effect, can, in the
presence of certain chemical agents, result in injury to tissues
(phototoxicity, photoallergy, enhancement of
photocarcinogenesis).
10. BIOLOGICAL EFFECTS OF ULTRAVIOLET
RADIATION ON UNICELLULAR ORGANISMS,
MAMMALIAN CELLS AND TISSUE, AND
INVERTEBRATES
Question 2
11. Molecular lesions in DNA
Deoxyribonucleic acid (DNA) is one of the most important target
molecules for photobiological effects.
A lesion in a cell
genome is always serious, because, in general, the genome exists only
in one copy in the cell concerned, whereas a lesion in a protein, even
of the same magnitude, may remain undetected because there are
many copies of the proteins. The latter is also true of ribonucleic
acids (RNA).
Most studies have been performed with low pressure mercury arcs
emitting primarily UVR of 254 nm.
12. The most common changes produced in DNA are damage to the bases and
to the polynucleotide chains. Damage to the bases may be unimolecular or
bimolecular. Since pyrimidine bases are ten times more sensitive to UVR
than purine bases, the only unimolecular reaction discussed will be the
formation of pyrimidine hydrates.
Bimolecular reactions are very numerous. They may occur between two
bases, or between a base and another molecule. The most important effect
is the formation of dimer compounds, particularly thymine dimers. The
dimer brings about a twisting of the secondary helical structure of DNA and
causes local denaturation. New biochemical methods have made it possible
to detect dimers in vivo in all types of irradiated cells studied. The number
of dimers has been shown to be proportional to the dose of UVR and to vary
with wavelength with a peak at 280 nm. It is not the only serious lesion
produced in DNA by UVR.
13. Polynucleotide chain breaks represent another type of lesion that
may occur in DNA. The proteins that make up the bulk of the cell
may sustain damage to the secondary or tertiary structures.
Breaks may occur in peptide chains or bonds or cross-links.
The distortion produced in the DNA-molecule prevents it from
carrying out its functions, i.e., transcription and replication may
be blocked. These lesions can be recognized by repair enzymes or
may act as a signal for other biological processes to intervene.
They may result in cell death, genetic recombination,
mutagenesis, or even carcinogenesis.
14. Effects on bacterial cell constituents
Apart from chromosomes, structures containing
membrane-bound DNA and structures containing RNA are
the main targets for UVR induced lesions, which are
reflected in alterations in the templates needed for
macromolecular syntheses.
DNA synthesis is first blocked, at least for a time. The
blockage is photoreversible. Changes in other biochemical
constituents of varying importance may occur.
15. Functional alteration is shown by a slowing-down of
the growth rate of bacteria, which may also grow
abnormally without dividing into filaments. Survival is
evaluated on the basis of counting the colonies that
can be formed by surviving cells.
A cell irradiated at 254 nm to tolerate 5,5 times as
many dimers as one irradiated at 365 nm. To kill
E.coli, a dose of UVR-A one thousand times greater
than that of UVR-C or UVR-B is required.
16. The UVR resistance or IJVH sensitivity of the various
bacterial mutants depends on the genetic make-up of
the species concerned.
The IJVR doses that have to be used to produce the same
effect, and the number of dimers, the induction and
excision rate of which are responsible for this sensitivity,
vary considerably.
17. Yeasts
• Yeasts are microorganisms but are
nevertheless eukaryotic cells.
• Genetic analysis has shown that several
recessive genes are involved in the control of
responses mutagenesis, and recombination in
a way that is already much more complex than
that found in bacteria.
18. Effects on Mammalian Cells in Culture
An attempt has been made to apply the knowledge of
the mechanisms of photolesion formation and repair
discovered in microorganisms to a model more similar to the
human body; namely established strains of mammalian cell
cultures.
The strains most commonly used are HeLa (human
cells of cancerous origin), mouse L- fibroblasts and Chinese
hamster cells. The ability of a surviving cell to form a colony
and the numerous parameters used in radiobiology have been
widely used to study the effects of UVR on this material.
19. The most marked effects of UVR on cells are death, mutagenesis,
and malignant transformation. Sublethal effects include various degrees of
inhibition of growth and colony-forming ability. At low doses, the growth of L
fibroblasts is merely slowed down. Higher doses, however, bring about lysis
of the cells.
Studies of the effects of IJV-A on bacteria have made it possible
to elucidate, at least in part, the complex phenomena that occur in
mammalian cells. Cells can be damaged by UVR-A or visible light (300-420
nm with a peak at 365 nm).
Evaluation of viability with trypan blue stain showed that, after
exposure to 2 X 10 4 Jm 2 , 99 % of human cells, 90 % of mouse cells, and 50 %
of hamster cells were destroyed.
The fact that survival depends on the density of the cell population
suggests that perhaps some of the effects of UV-A are indirect.
20. Sensitivity to viral infection
• Infection with herpes virus is enhanced in
mammalian cells exposed to UVR-A.
• Relatively low exposures increase infectivity by
20-30 % and it remains high for several days.
21. Activation of viruses
• Since some mammalian cells harbour viruses that normally
remain latent, their activation or induction might transform
them and endow them with the characteristics of cancer
cells, UVR-C exposure of rat or hamster cells, transformed
by certain oncogenic viruses, can activate the production of
virus particles, whereas irradiation of normal cells can
activate tumour viruses of the leukemia-leukosis type.
• However, there is nothing to show that malignant
transformation necessarily involves the development of an
oncogenic virus.
22. Effects on eggs and embryos of
invertebrates
• The others must be stripped or dechorionated by physical or
chemical means. The whole egg or part of an egg has been
irradiated with UVR mainly to destroy certain cells, in order to watch
how development proceeds in their absence and thus deduce the
role they play. Wavelengths of 225-313 nm have caused appreciable
delays in development. Undivided eggs have been shown to be
highly sensitive to UVR.
• There has been very little work using UVR-A. In conclusion, it may
be said that, in general, eggs are well protected against the harmful
effects of UVR. If they are directly exposed, they respond to UV
irradiation by means of the mechanisms already described.
25. The longer the wavelength of light, the deeper the
penetration of the light into the skin.
Ultraviolet light is generally divided into ultraviolet
C (200 to 280 nanometers), ultraviolet B (280 to
320 nanometers), and ultraviolet A (320 to 400
nanometers).
Of the light that reaches the surface, ultraviolet B
(mid-wavelength ultraviolet light) appears to be
the most carcinogenic.
26. Beneficial Effects
• In addition to the direct effects on the skin, UVR
produces a number of systemic effects. It has the
capacity to increase the tonus of the sympathico-
adrenal system, enhances mitochondrial and
microsomal enzyme activity and the non-specific
immunity level, and increases the secretion of a
number of hormones.
27. Systolic and diastolic blood pressures are reduced before
sunburn appears and may even be reduced with exposures so
mild that no visible erythema is produced .
Blood pressure gradually falls for 24 hours, and lowered
pressure may persist for several days. Studies have
demonstrated that the exercise tolerance of children receiving
UVR through the winter is greater than that
of control groups not receiving radiation.
28. Seasonal changes in various diseases are often considered to
be evidence of IJVR effects, but there are many other climatic
variables that change with the season, including temperature
and daylength. Blood volume, blood content of the skin,
blood flow in the skin, and hydration of the skin due to
sweating vary with seasonal adaptation. Thus few changes in
disease patterns can be attributed to the effects of UVR
alone.
29. • Ultraviolet radiation – the most biologically active part of the solar
spectrum, significantly affects the physiological reactions of tissues and
the whole body, is in the wavelength range of 10-400 nm.
• With very intense radiation, painful redness of the skin and sunburn
appear. If there is no infection, then the blisters pass without a trace. If a
large surface of the skin has been exposed to intense radiation, the
consequences can threaten people's lives.
• In such overexposed people, the body burns, the temperature rises at
night, headache, insomnia, chills, nausea, irritability appear, there is a
burning sensation of the skin and itching throughout the body, muscles
and even bones ache, appetite is lost. Often, overexposure leads to
overheating of the body and heat stroke. Since there are a lot of
ultraviolet rays in the scattered solar radiation, it is possible to tan in
cloudy weather and get sunburn, even while in the shade.
30. The erythemic sensitivity of individual parts of the human
body decreases in the followingsequence:
• chest,
• abdomen,
• back,
• neck,
• face,
• upper
• lower extremities.
The sensitivity of the face is about 25 %, and the neck is
about 50 % of the sensitivity of the chest.
31. • The biological effect of ultraviolet rays (UVL) is very diverse. This can be both
positive and destructive. The most dangerous consequences of exposure to short-
wave ultraviolet radiation (10-200 nm), the vast majority of which is retained in
the upper layers of the atmosphere, in particular, in its ozone layer.
• However, the risk of damage by UV radiation occurs during prolonged exposure
to the Sun, as well as in industrial conditions when working with artificial sources
of UV radiation (electric welding), conducting physiotherapy procedures
(therapeutic, preventive ultraviolet radiation).
• Ultraviolet radiation has an adverse effect on the eyes. An increase in the dose of
ultraviolet radiation leads to the denaturation of the protein. With a significant
dose of radiation, after a latent period of several hours, inflammation of the
cornea of the eye (keratitis)occurs or the mucous membrane
(conjunctivitis).Acute pain and an unpleasant sensation of a foreign body last 1-2
days. Therefore, when working with ultraviolet radiation, it requires the
protection of the visual analyzer .
32. The destructive effect of UFL is used in human practice. In particular,
their destructive effect on microbial cells (bactericidal effect at a
wavelength of 180-280 nm, maximum-at 254 nm) is widely used for
improving the air, maintaining an antimicrobial regime in the premises
of medical institutions, disinfection of water. The ability of various
media to glow under the influence of ultraviolet radiation is used in
analytical chemistry. For example, the luminescent method is used to
determine vitamins in food raw materials and food products.
33. The carcinogenic effect of solar radiation is also caused by ultraviolet radiation.
Skin cancer is common in all peoples, but the frequency of diseases in different
countries is very different. In the appropriate climate and for a susceptible
race, skin cancer is a serious medical problem.
People with fair skin who receive large doses of ultraviolet radiation are more
susceptible to this disease. When moving to low latitudes, people's skin
relatively slowly acquires protective properties (an increase in the degree of
pigmentation), which increases the risk of disease.
In the Hawaiian Islands, skin cancer among Europeans is 42 times more
common than in the indigenous population. In Kazakhstan, Kazakhs suffer from
skin cancer 10 times less often than visitors. In Australia, the Irish and Scots are
more susceptible to it, then the Germans and Scandinavians, less the English
and Slavs, and extremely rarely – the inhabitants of China and the local
population.
34. The sun's ultraviolet radiation
protection measures:
Limit your time in the midday sun. The sun's ultraviolet radiation is most intense from
10 am to 4 pm. Be especially careful when in the sun during these hours.
Keep an eye on the UV index. This important indicator will help you plan your outdoor
activities to prevent excessive exposure to the sun. At a moderate UV index, i.e. 3 or
higher, sun protection is required.
Use the shadow wisely. Try to stay in the shade at the time when the UV rays are most
intense, but keep in mind that shade from trees, umbrellas, canopies, etc. does not
provide complete protection from the sun.
Wear protective clothing. The wide-brimmed hat provides reliable sun protection for the
eyes, ears, face and back of the neck. Sunglasses that provide protection from UV-A and
UV-B by 99% -100%, significantly reduce the harmful effects of the sun on the eyes.
Dense and spacious clothing that covers as much of the body as possible provides
additional protection from the sun.
35. The sun's ultraviolet radiation
protection measures:
Use sunscreen. Apply a broad-spectrum sunscreen with a protection
factor of SPF 30+ to exposed skin every 2 hours or after working,
swimming, playing games or playing outdoor sports.
Do not use artificial tanning equipment or lamps. Artificial tanning
equipment and lamps increase the risk of skin cancer and can
damage unprotected eyes. Their use should be completely excluded.
Protect your children. Children tend to be more sensitive to
environmental hazards than adults. During outdoor activities, they
should be protected from intense UV exposure, as indicated above,
and babies should always be in the shade.
36. • However, for residents of the North and the
Arctic, as well as for people working in mines,
engine rooms, holds, dark workshops and other
rooms deprived of natural light, the
consequences of restricting or completely
excluding access to light are often manifested in
the exacerbation of chronic diseases.
• This phenomenon is called the light starvation
syndrome.
37. Light starvation syndrome is
characterized by the following main disorders:
* reducing the body's resistance;
* disorders of the nervous system function;
* metabolic disorders;
* decrease in the body's vitamin supply;
* decrease in the protective function of the skin, increase its sensitivity to irritating
effects, the development of pyoderma;
* reduced physical and mental performance;
* inhibition of bone consolidation processes in fractures, wound healing;
• development of dental caries;
* exacerbation of chronic diseases;
* development of toxicosis of endogenous origin (endotoxicosis);
* visual analyzer malfunction
38. Prevention of the development of light starvation syndrome consists of the
following measures
* rational planning of populated areas, individual buildings and premises in order to increase insolation;
* creation of parks and recreation areas;
* longer outdoor exposure;
* installation of aerariums and tanning salons;
* radiation exposure in photariums with a strict dosage of UVL;
* the use of UV light sources in rooms for various purposes with the mandatory separate inclusion of
conventional lighting and UV light sources;
* performing physical therapy using UFL to accelerate the consolidation of fractures, wound healing;
* rationalization of nutrition, especially for protein, mineral and vitamin components;
* creating normal social and living conditions.
40. Application of ultraviolet radiation
The wide biological effect of ultraviolet rays makes it possible to use them in certain
doses for preventive and therapeutic purposes.
For ultraviolet radiation, use sunlight, as well as artificial sources of radiation:
mercury-quartz and argon-mercury-quartz lamps. The radiation spectrum of mercury-quartz
lamps is characterized by the presence of shorter ultraviolet rays than in the solar spectrum.
Ultraviolet radiation can be general or local. The dosage of the procedures is made
according to the principle of biodose.
Currently, ultraviolet radiation is widely used, primarily for the prevention of various
diseases. For this purpose, ultraviolet radiation is used to improve the human environment
and change its reactivity (first of all, to increase its immunobiological properties).
41. • With the help of special bactericidal lamps, the air can be sterilized in
medical institutions and residential premises, the sterilization of milk, water,
etc. Ultraviolet radiation is widely used to prevent rickets, influenza, for
general strengthening of the body in medical and children's institutions,
schools, sports halls, fotarium at coal mines, when training athletes, for
acclimatization to the conditions of the north, when working in hot shops
(ultraviolet radiation gives a greater effect in combination with exposure to
infrared radiation).
Ultraviolet rays are especially widely used to irradiate children. First of all,
such radiation is indicated for weakened, often ill children living in northern
and middle latitudes. At the same time, the general condition of children
improves, sleep, weight increases, morbidity decreases, the frequency of
catarrhal phenomena and the duration of diseases decreases. Improves overall
physical development, normalizes blood, vascular permeability.
42. Ultraviolet irradiation of miners in photariums, which are organized in
large numbers at mining enterprises, has also become widespread. With
systematic mass exposure of miners engaged in underground work, there is an
improvement in well-being, an increase in working capacity, a decrease in
fatigue, a decrease in morbidity with temporary disability. After irradiation of
miners, the percentage of hemoglobin increases, monocytosis appears, the
number of cases of influenza decreases, the incidence of the musculoskeletal
system and the peripheral nervous system decreases, pustular skin diseases,
catarrh of the upper respiratory tract and angina are less frequent, the
indications of vital capacity and lungs improve.
43. Negative effects of chronic exposure to
ultraviolet radiation
Long-term exposure to solar UV radiation can lead to acute and chronic health
consequences – for the skin, eyes, and immune system. Sunburn, or erythema, is the
most well-known acute consequence of excessive UV exposure. With very long-term
exposure, UV radiation causes degenerative changes in skin cells, fibrous tissue and
blood vessels, such as freckles, birthmarks, and small dots (i.e., pigmented areas of the
skin). This leads to premature skin aging, photodermatosis, and actinic keratosis.
Approximately 2 to 3 million cases of non-melanoma skin cancers (such as basal
cell carcinoma and squamous cell carcinoma) are diagnosed each year, but these
cancers are rarely fatal, and surgery is successful in these cases.
Each year, around 130,000 cases of malignant melanoma are reported worldwide,
which significantly increases the mortality rate among population groups.
44. In addition, there is growing evidence that levels of ultraviolet radiation in the environment can
suppress cellular immunity, thereby increasing the risk of infectious diseases and limiting the
effectiveness of vaccination. Both affect the health of the poor and vulnerable, especially children in
developing countries. Many of these countries are located close to the equator, so their populations are
exposed to the very high levels of ultraviolet radiation characteristic of such regions.
There is a widespread misconception that only people with light skin types should worry about
excessive sun exposure. Yes, dark skin has more of the protective pigment melanin, and the incidence of
skin cancer among the dark-skinned population is lower. However, skin cancers also occur in this
population, but unfortunately, they are often detected at a later and much more dangerous stage. The risk
of harmful effects of UV radiation on the eyes and the immune system does not depend on the type of
skin.
45. The use of artificial sources of short-wave ultraviolet
radiation for disinfection of environmental objects
The most practical importance is the use of bactericidal lamps for disinfection (sanitation) of air in
closed rooms with a large crowd of people: waiting rooms of polyclinics, group rooms of kindergartens,
rooms for recreation in schools, etc. Disinfection of indoor air with BUV lamps is carried out either in the
presence of people, or without them.
It is most effective to carry out air disinfection in the presence of people, since people are the main
source of indoor air pollution. To do this, the upper zone of the premises is irradiated with bottom-
shielded BUV lamps. Shielded lamps are suspended at a height of about 2.5 m from the floor in places of
the most intense convection currents of air (above heating appliances, doors, etc.). The radiation power of
BUV lamps is proportional to the POWER consumed by the lamp from the mains. When calculating a
bactericidal installation, it is necessary that 0.75—1 W of power consumed by the lamp from the mains
should be accounted for per 1 m3 of the volume of this room.
46. Example 1. To disinfect the air of a room with a volume of 250 m3, it is necessary to equip it with
an installation with BUV-15 lamiami. Air disinfection will be carried out in the presence of people.
Calculate the required number of BUV-15 lamps. Where and how should they be placed ?
Decision. To disinfect the air of the specified room, it is necessary to create an installation with a
total power of 187-250 watts. This requires 12-16 BUV-15 lamps (185 W : 15 W =12; 250 W:15 W =
16).
The time of exposure to air in closed rooms should not exceed 8 hours per day. It is best to irradiate
3-4 times a day with breaks to ventilate the room, as ozone and nitrogen oxides are formed, which are felt
as a foreign smell. Disinfection of indoor air in the absence of people is usually carried out in the
premises of bacteriological laboratories, in operating rooms, dressing rooms and other rooms after wet
cleaning. In these cases, open lamps are placed either evenly throughout the room, or mainly above the
work tables. As a rule, a lamp is also placed over the door, creating a "curtain" of bactericidal rays.
47. The number of lamps and the time of disinfection depend on the mode of this
room. The minimum number of lamps should be such that at least 1.5 W of power
consumed from the network per 1 m3 of room volume; the minimum irradiation time is
15-20 minutes.
Disinfection of indoor air with PRK lamps can be carried out in the presence or
absence of people. To do this, the lamp is installed at a height of 1.7 m from the floor
with the reflector facing up. For 1 m3 of room volume, there should be 2-3 W of power
consumed from the network. Air irradiation is carried out for 30 minutes several times
a day at intervals used to ventilate the room. Disinfection of the air with PRK lamps
can be carried out in breaks between work in institutions, when children go for a walk,
etc. For 1 m3 of room volume, when air is sanitized in the absence of people, 5-10
watts of lamp power can be accounted for. The time of exposure to the air in the
absence of people should be as long as possible.
48. Bactericidal lamps made of uviol glass B U B (DB) are sources of
ultraviolet radiation in the region C. The maximum radiation of BUV
lamps is 254 nm. Lamps are used only for disinfection of objects of the
external environment: air, water, various objects (dishes, toys).
Exposure of people to direct rays from these lamps is not allowed. In
the case of irradiation of people, the same adverse events may occur
as in the case of overexposure to PRK lamps (photophthalmia, etc.).
BUV lamps are made of uviol glass and filled with argon with a
dosed amount of mercury at low pressure. They produce lamps with a
power of 15 W (BUV-15), 30 W (BUV-30, DB-30-1), 60 W (BUV-60, DB-
60), 30 W with an increased current density (BUV-30-I).
