METEOROLOGICAL ENVIRONMENT Lec -7-
RADIATION &Learning objectives
At the end of this lecture student will be able to : 1-Classify sources of radiation . 2-Identify types of radiation . 3-Enumerate biological effects of radiation & radiation protection . 4-Determine elements of meteorological environment . 5-Specify effects of atmospheric pressure on health . 6-Discuss effect & preventive measures of air temperature . 7-Clarify climate related terms & parameters . To a level accepted to the accreditation standard of the College .Sources of radiation:
Radiation is part of man’s environment. The sources of radiation to which man is exposed are divided into two groups:A.Natural sources: It arises from :1.Cosmic rays: . Which originate in outer space and weakened as they pass through the atmosphere.2. Environmental:a: Terrestrial radiation : Radioactive elements such as thorium, uranium, radium &an isotope of potassium, are present in man’s environment, e.g. soil, rocks, buildings .b: Atmospheric radiation: The external radiation dose from the radioactive gases radon& thoron in the atmosphere is rather small. 3.Internal radiation : Man is also subjected to internal radiation i.e. from radioactive matter stored in the body tissues. It is estimated that the total natural radiation to which the average person is subjected comes to approximately 0.1 rad a year.
B.Man-made Sources: these are: 1. Medical and dental: (X-rays and radioisotopes ) The greatest man-made source of radiation exposure to the general population at the present time is medical& dental X-rays. Two distinct groups are involved (patients and radiologists & medical technicians) 2. Occupational exposure: 3. Nuclear: radioactive fallout Nuclear explosion release a tremendous amount of energy in the form of heat, light, ionizing radiation & many radioactive substances.
4.Miscellaneous: Some every day appliances (e.g. TV sets , luminous wrist watches) are radioactive. But radiation from these sources at present time is too small to be important .
Types of radiation
A. Ionizing radiation : applied to radiation which has the ability to penetrate tissues & deposit its energy within them. Ionizing radiation divided into two groups: 1.Electro-magnetic radiation: X-rays& gamma rays. 2.Corpuscular radiation: alpha, beta particles & protons. B. Non ionizing radiation : it refers to several forms of electromagnetic radiation of wave lengths longer than those of ionizing radiation . It includes UV radiation, visible light, infrared radiation, microwaves &radio frequency radiation.
Biological effect of radiation
A. Somatic effects: 1. Immediate: a. Radiation sickness. b. Acute radiation syndrome. 2. Delayed: a. Leukemia b. Carcinogenic c. Fetal developmental abnormalities d. Shortening of life. B. Genetic effect: 1. Chromosome mutations. 2. Point mutations.Radiation protection
Radiation protection is the youngest branch of hygiene &is called radiation-hygiene . The International Commission on Radiological Protection (ICRP) ,the International Atomic Energy Agency (IAEA)& the WHO have been active in this field. It has been recommended that the genetic dose to the whole population from all sources additional to the natural background radiation should not exceed 5rems over a period of 30 years.Meteorological environment
Meteorological environmentThe elements of metrological environment are:1.Atomospheric pressure.2.Air temperature.3.Humidity.4.Rainfall.5.Direction &speed of wind.6.Movement of clouds & character of weather.The term “climate” is a geographical concept representing a summation of the whole range of meteorological phenomena .
Atmospheric pressure:
Man is physiologically adapted to live at 760 mm of Hg pressure or close to it.The atmospheric pressure falls as altitude increase, & rises as altitude decrease.Thus at an altitude of 100000 feet above mean sea level, the atmospheric pressure is less than 10 mm of Hg.Pressure increase at the rate of one atmosphere for each 33 feet depth below sea level.The instruments used for measuring atmospheric pressure are known as barometers (Fortin’s , Kew Pattern Station & Barograph).Effect of atmospheric pressure on health:
High altitude: The air is less dense at higher altitude so the partial pressure of oxygen is also less. Man can not survive at an altitude of 25000 feet without breathing equipment. When man is exposed to low pressure, the physiological effect are: 1) increase in respiration. 2) increase in the concentration of hemoglobin 3) increase in cardiac out put. Sudden exposure to high altitude leads to : 1.Acute mountain sickness. 2.High altitude pulmonary edema.
Low Altitude
When man is exposed to high pressure, the gases in the air namely oxygen, CO2 & nitrogen are dissolved in the blood & tissues, proportionately to the partial pressure of these gases. When the person comes up to the surface, the gases which are dissolved in the blood under pressure are released & cause air embolism.. The effect of increased pressure are best observed in person working in diving bells & compressed air chambers (Caisson disease).Air Temperature:
The temperature of air varies in different parts of the day& also in the different seasons. The factors which influence the temperature are latitude of the place, altitude, direction of wind & proximity to sea. Thermometers are instruments used for measuring temperature (mercury & alcohol). Alcohol thermometers not solidify even at lowest temperature . 1. Air should have free access to the bulb . 2. Thermometer should be protected against radiant heat .Effect of heat stress
Important disorders resulting from exposure to heat , are : 1.Heat stroke. 2.Heat hyperpyrexia. 3.Heat exhaustion. 4.Heat cramps. 5.Heat syncope. Preventive measures: The ill effect of high temperature may be prevented by observing the following precautions: 1.Replacement of water. 2.Regulation of work. 3.Clothing. 4.Protective device. 5.Work environment which controlled by proper ventilation.Effect of cold stress
A- General cold injury (hypothermia), the individuals said to be suffering from exposure to cold. This is characterized by numbness, loss of sensation, muscular weakness, desire for sleep, coma& death. B-Local cold injury may occur at temperatures above freezing (wet-cold conditions) as in immersion or trench foot . At temperature below freezing (dry-cold conditions) frostbite occurs, the tissues freeze& ice crystals form in between the cells. Frostbite is common at high altitudes . It is extremely important to dress for the temperature with which the part will be in contact . The affected part should warmed using water at 44 oC . Warming should last about 20 minutes at a time. Intake of hot fluids promotes general re-warming .Global warming
Emission of green-house gases into the atmosphere have been increasing ever since the beginning of the industrial revolution. It is generally conceded that the main effect of this include an increase of about 3 oC in the average global surface temperature by the year 2030, a rise in the sea level of 0.1-0.3 meters by 2050 & an increase in the occurrence of extreme climatic events such as cyclones, heat waves &draughts. The temperature rise could overwhelm the capacity of many species to adapt .A change of this magnitude would affect local, regional & global ecosystem, sea levels & ocean currents, prevailing winds, fresh water supplies, agriculture, forests, fisheries, industry, transport, urban planning, demographics & human health .Changes in the configuration of jet streams, prevailing winds and ocean currents could alter the distribution of rainfall in many regions, making some wetter, others drier . Summers are becoming hotter . Temperature zone warming induces a decline in soil moisture that impairs grain production . This will change the distribution of vegetation & insect vectors of disease .The “heat island” phenomenon that makes cities warmer than surrounding rural areas will lead to longer and more severe heat waves than we are accustomed to now .