Lecture 2 Chemical and Biological Agents

Transcription

1 Lecture 2 Chemical and Biological Agents

2 In the Chemical ad Biological section, Routes of exposure we will be covering: Forms of Chemical agents Examples of chemical agents Forms of Biological agents Classifications of hazardous substances Major systems affected by the chemical and biological agents

3 Routes of entry to human body There are three principle routes of entry of hazardous substances to human body: Inhalation Absorption through the skin Ingestion Injection

4 Routes of entry to human bodyinhalation Breathing in the substance with normal air intake- main route of contaminant to body. These contaminants can be chemical or biological. They enter the lungs where they have access to bloodstream and many other organs

5 Routes of entry to human bodyabsorption through skin The substances come into contact and enter through wounds or pores Examples are tetanus, toluene and benzene Injection: rare but possible entry method. Examples are accidents involving hypodermic syringes in health service

6 Routes of entry to human bodyingestion Through the mouth and swallowed into the stomach and the digestive system This is not a common route of entry in occupational exposure The most common occurrence are through poor personnel hygiene and air borne dust

7 Forms of chemical agents Chemicals can be transported in a variety of forms: Dusts Gases Vapors Liquids Mists Fumes

8 Forms of chemical agents-dusts Dusts are solid particles slightly heavier than air so they get suspended in air for a short period of time. Dusts are created by mechanical process (grinding) or construction and demolition The size of particle range from about 0.4 mm (fine) to 10 mm (coarse). The fine dust is more harmful because it penetrates deep into the lungs and remain there-usually known as respirable dust. E.g cement and silica dust. Repeated exposure may lead to permanent lung disease

9 Forms of chemical agents-gases Gases: Any substance at a temperature above their boiling points Gases are absorbed into the blood stream where they may be beneficial (O2) or harmful (CO)

10 Forms of chemical agents-vapours Vapours are substances which are at or very close to their boiling points. They are gaseous in form. Examples are many solvents and cleaning fluids They enter the bloodstream and can cause short term effect (diziness) or long term (brain damage)

11 Forms of chemical agents-liquids Substances that exists in temperature between the freezing point and boiling points. In health and safety regulations the term fluid is used. They enter the body through all routes of exposure.

12 Forms of chemical agents- Fumes A collection of very small metallic particles (less than 1 mm) which have condensed form the gaseous state. They are mostly generated from welding process. The particles tend to be in the respirable range (0.4 to 1mm) and can lead to long term permanent lung damage The exact nature depends on the metal and the duration of exposure.

13 Forms of chemical agents- Mists Mists are similar to vapor in that they exist in or near their boiling temperatures but are closer to the liquid phase. There are very small liquid droplets in the vapour. Mists are produced during spraying (e.g paint spraying) They can be inhaled, or enter the body through skin or ingestion

14 Forms of biological agent Biological Hazard can be transported by any of the following forms of agent: Fungi and moulds Bacteria Viruses

15 Forms of biological agent-fungi Fungi are very small organisms that could be single cell or multiple cells. They live on dead organic matter or living animals and plants as parasites. Some fungi are beneficial such as penicellium Fungi reproduce by producing spores which can cause allergic reactions when inhaled The infection in man by fungi can be mild (athletic foot) or severe such as ringworm.

16 Forms of biological agent- Bacteria Bacteria are very small single-celled organisms which are much smaller than human cells. Some bacteria are beneficial such as bacteria that live aid the digestion of food in adults and babies. Bacteria are treated by antibiotics but through misuse they are becoming resistant. Examples of bacterial infection legionella, tuberculosis and tetanus

17 Forms of biological agent- Viruses Viruses are minute non cellular organisms, much smaller than bacteria. They appear in various shapes and continuously developing new strains. They can not be treated by antibiotics and can only be defeated by the defense mechanism of the human body. Examples of viral infections: common cold, influenza, hepatitis and AIDS (HIV).

18 Classification of hazardous substances A hazardous substance is one which can cause ill health to people at work. They are classified according to the severity and type of hazard they may present. The most common classifications are: irritant Corrosive Harmful Toxic carcinogenic

19 Classification of hazardous substances-irritant Irritant is a non corrosive substance which can cause skin and lung inflammation People who react are sensitized or allergic to that substance The effect depends on the concentration and exposure time, in most cases concentration being more significant. Examples are bleaches, glues, solvents and formaldehyde

20 Classification of hazardous substances-harmful It is referred to a substance, which if entered the body may pose limited health risks. Many household substances are classified as harmful, such as bitumen-based paints. Many substance that are classified as harmful can be classified as irritant.

21 Classification of hazardous substances-corrosive These are substances that will attack normally by burning living tissue They are strong acids and strong alkali. Examples are sulphuric acid and caustic soda. Tough cleaning substances are corrosive.

22 Classification of hazardous substances- A substance which impede or prevent the function of a body organ. Lead, mercury, pesticide and carbon monoxide are toxic substances Toxic

23 Classification of hazardous substances- Carcinogenic Are substances that are known or suspected to cause abnormal development of body cells to become cancers. Examples are Asbestos, hard wood dust and some mineral oils

24 Effects of hazardous substances-acute and Chronic The effects of hazardous substances can be either acute or chronic: Acute are of short duration and appear fairly quickly from the onset of exposure. They may be severe and require hospitalization but usually reversible. Chronic effects develop over period of time to repeated exposure. Symptoms appear over years and are usually irreversible

25 The major functional systems affected by hazardous substances The respiratory system The nervous system The cardiovascular system The urinary system The skin

26 Respiratory system

27 The respiratory system Soluble dusts get absorbed to the blood stream, insoluble dust remains in the lung leading to chronic illness. The cilia offer some protection against insoluble dust by trapping them and passing them with the aid of the mucus back to the throat. It has been shown that smoking damages this mechanism The nose will normally trap larger particles

28 Effects on the respiratory system Respirable dust puncture the alveoli walls producing scar tissues upon healing causing fibrosis. Acute effects include bronchitis and asthma, chronic fibrosis and cancer. Asphyxiation occurs due to lack of oxygen in confined spaces, particularly with metal inert gases at welding

29 The nervous system The nervous system consisst of the brain, spinal cord and nerves extending throughout the body. It controls muscle movements and sensations. Neurotoxins affect the nervous system and lead to changes in mental ability (loss of memory and anxiety), epilepsy and narcosis

30 The cardiovascular system The blood system uses the heart to pump blood through arteries, veins and capillaries. Blood is produced in the bone marrow and consists of red blood cells, white blood cells and platelets. The basic functions of the blood system. Benzene affects the bone marrow thus reducing blood cells CO prevent RBCs from absorbing O2 Symptoms begin with headaches and end with unconsciousness and possibly death

31 Excretory organs-liver Liver: remove toxins from the blood, maintains sugar and produces proteins for the blood plasma. Hazardous substances can cause liver to be too active or inactive. Xylene cause liver enlargement Alcohol causes cirrhosis Vinyl chloride causes cancer

32 Excretory organs-kidney The kidneys filter waste from the blood as urine, regulate blood pressure and liquid volumes. Heavy metals (lead and cadmium) and organic solvents (glycol ethers) can restrict the operation of kidneys and lead to failure.

33 The skin The skin holds the body together and is the first line of defense. It regulates the body temperature, conserves water and provides emergency food store. The most common industrial disease is Dermatitis. (symptoms) There are two types: Irritant contact dermatitis: onset of contact, condition reverse after contact ceases (eg detergents) Allergic contact dermatitis caused by sensitizers such as solder flux, formaldehyde

34 Next Lecture Next lecture we will talk about: Specific biological and chemical hazards (most common in the workplace Control of substance hazardous to health (COSHH) regulations Risk assessment according to COSHH Control measures required under COSHH Regulations

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