You have been hired as a medical consultant for a preschool director. Your first job is to advise the director about the amount of ultraviolet exposure that is safe for the children. In your report discuss: electromagnetic radiation, ionizing and non-ionizing radiation, types of UV, effects of UV on biological tissues, atmospheric propagation and measurement of UV, regional, daily and seasonal variations in UV levels, mechanism of sunscreens protection, propagation of E/M waves through biological tissues.
Electromagnetic radiation:
EM radiation or EMR refers to the waves of the electromagnetic field, propagating, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, visible light, ultraviolet (UV), X-rays, and gamma rays. Electromagnetic waves travel at the speed of light, commonly denoted 'c'. In homogeneous, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave.
The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves of different frequency are called by different names since they have different sources and effects on matter. In order of increasing frequency and decreasing wavelength these are: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
Ionising Radiation:
Any type of electromagnetic radiation that carries enough energy to ionise or remove electrons from an atom is called an ionising radiation. They can be of two types, e.g. X-rays and Gamma Rays, which often have the same energy. Common ionising particles from radioactive decay are Alpha Particles, Beta particles and Neutrons. Generally all particles from a radioactive decay are ionising because their energy is generslly much higgher than that required for ionising an atom.
Ionizing radiation is harmful and lethal to living beings but some types have applications in radiation therapy for the treatment of cancer. Most adverse health effects of exposure to ionizing radiation are:
a. Harmful tissue reactions due in large part to killing or malfunction of cells following high doses from radiation burns.
b. Stochastic effects, i.e., cancer and heritable effects involving either cancer development in exposed individuals owing to mutation of somatic cells or heritable disease in their offspring owing to mutation of reproductive (germ) cells.
Non-ionising Radiation:
Non-ionising radiation refers to any type of electromagnetic radiation that does not carry enough energy to ionize atoms or molecules - that is, to completely remove an electron from an atom or molecule. Instead of producing charged ions when passing through matter, non-ionizing radiation has energy only for excitation, the movement of an electron to a higher energy state.
In terms of potential biological effects, the non-ionizing portion of the spectrum can be subdivided into:
a. The optical radiation portion, where electron excitation can occur (visible light, infrared light).
b. The portion where the wavelength is smaller than the body. Heating via induced currents can occur.
c. The portion where the wavelength is much larger than the body, and heating via induced currents seldom occurs.
Types of UV Rays:
The three types of UV radiation are classified according to their wavelength. They differ in their biological activity and the extent to which they can penetrate the skin. The shorter the wavelength, the more harmful the UV radiation. However, shorter wavelength UV radiation is less able to penetrate the skin.The ultraviolet (UV) rays produce UV radiation, which has three main components: ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC).
UV radiation
What is the difference between UVA, UVB and UVC?
The three types of UV radiation are classified according to their wavelength. They differ in their biological activity and the extent to which they can penetrate the skin. The shorter the wavelength, the more harmful the UV radiation. However, shorter wavelength UV radiation is less able to penetrate the skin.
a. Short-wavelength UVC is the most damaging type of UV radiation. However, it is completely filtered by the atmosphere and does not reach the earth's surface.
b. Medium-wavelength UVB is very biologically active but cannot penetrate beyond the superficial skin layers. It is responsible for delayed tanning and burning.
c. The relatively long-wavelength UVA accounts for approximately 95% of the UV radiation reaching the Earth's surface. It can penetrate into the deeper layers of the skin and is responsible for the immediate tanning effect. Furthermore, it also contributes to skin ageing and wrinkling.
Effects of UV rays on Biological Tissue:
A. Beneficial Effects: UV light causes the body to produce vitamin D (specifically, UVB), which is essential for life. The human body needs some UV radiation in order for one to maintain adequate vitamin D levels.Vitamin D promotes the creation of serotonin, which creates the sensation of happiness.
B. Harmful Effects: Excessive exposure to UV radiation can result in acute and chronic harmful effects on the eye's dioptric system and retina. It can also cause sunburn but also some forms of skin cancer.
UVB radiation can cause direct DNA damage.The most deadly form of skin cancer, malignant melanoma, is mostly caused by DNA damage independent from UVA radiation. Occasional over-exposure and sunburn are probably greater risk factors for melanoma than long-term moderate exposure.UVC is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic.
Measurement of UV Rays:
The intensity of UV radiation is measured in the units of milliwatts per square centimeter (mW/cm2) which is energy per square centimeter received per second. Also, it is measured in the units of millijoules per square centimeter (mJ/cm2), which is energy received per unit area in a given time.
You have been hired as a medical consultant for a preschool director. Your first job is...