W507 – Types of health effects

1. W507 – Types of health effects

2. Types of health effects • Asphyxiation • Irritation • Narcosis • Systemic toxicity • Genotoxicity and carcinogenicity • Sensitisation (allergic reaction) • Reproductive effects

3. Asphyxiation • Asphyxiants can reduce the level of oxygen in the body to dangerous levels • Two types – simple asphyxiants and chemical asphyxiants • Simple asphyxiants • Chemically inert – they reduce the amount of oxygen in the air by displacing it in an enclosed environment • Air normally contains 21% oxygen • If reduced below about 16% it can result in unconsciousness • At lower levels can lead to death • Examples include nitrogen, argon, helium, methane

4. Chemical asphyxiation • Prevent normal uptake or use of oxygen in the body • Haemoglobin in red blood cells, transports oxygen around the body as oxyhaemoglobin. • Carbon monoxide binds strongly with haemoglobin forming carboxyhaemoglobin. This reduces the amount of haemoglobin available to transport oxygen. • Hydrogen cyanide – fast acting asphyxiant that prevents normal uptake of oxygen into the cells

5. Irritation • An irritant can cause inflammation on contact with the skin or mucous membranes • Acute effects include • Skin – redness • Eyes – itchy, red or watery • Upper respiratory tract – coughing, sneezing (in severe cases lungs may produce excess fluid causing breathing difficulties • Examples include ammonia, chlorine, oxides of nitrogen etc

6. Irritation • Chronic exposure can also lead to other effects • Chronic exposure to respiratory irritant can cause bronchitis • Chronic exposure to skin irritants can lead to dermatitis – symptoms include dry flaking skin, itchy, redness, inflammation • Extreme form of irritation is from contact with corrosive substances that can cause tissue damage from which the tissues generally do not recover • e.g. concentrated acids, alkalis

7. Narcosis • A narcotic substance depresses the normal function of the central nervous system (CNS) • Symptoms may include • fatigue, headaches, light headedness and euphoria • at higher exposures dizziness, nausea, unconsciousness and death • A common group of substances found in industry that can cause narcosis are organic solvents

8. Systemic toxicity • Systemic toxicity - effects caused by a substance at organs remote from the point of contact • Effects may be caused by the substance or by its metabolites (breakdown products) • Due to metabolic processes liver and kidney particularly susceptible to damage by toxic substances

9. Carcinogenicity • Carcinogenicity – the ability of a substance (a carcinogen) to induce cancer • Cancer is a disorder of cells characterised by abnormal cell division and growth • It begins when one or more cells fails to respond to the normal control mechanisms and divide in an uncontrolled manner • Two main mechanisms by which cancer may be caused • Genotoxic mechanism • Irritant (non-genotoxic mechanism)

10. Genotoxicity and carcinogenicity • Genotoxicity – ability of a substance to induce damage to the genetic material in a cell • Such substances termed genotoxic or mutagenic • Can damage the genetic material in the cell and lead to irreversible changes called mutations • If mutations occur in germ cells they can be passed on to offspring where effects may be seen • If mutations occur in non-germ (somatic) cells, they may change the way that normal cell division is regulated so that it becomes uncontrolled and may lead to cancer

11. Genotoxicity and carcinogenicity • Non-genotoxic mechanism • Not all carcinogens are genotoxic (e.g. asbestos) therefore there must be another mechanism • Repeated damage to tissues may cause increased rate of cell division • Tissues are constantly being damaged and repaired - any increase in cell division may lead to a greater chance of mutations becoming permanent rather than be repaired

12. Genotoxicity and carcinogenicity • Benign tumours - e.g. warts, polyps and fibroids • May grow large enough to cause pain • Do not spread to other parts of the body • Usually not life-threatening, can generally be surgically removed • Malignant tumours • Can spread (metastasise) throughout body with development of secondary tumours • Tend to respond poorly to medical treatment • Usually life-threatening

13. Genotoxicity and carcinogenicity • Difficulties in identifying carcinogens • Many potential causes of cancer • Often difficult to prove a causal link between exposure to a substance and cancer • Often a long latent period between exposure and development of cancer • There is, however, significant evidence that cancer may develop after occupational exposure to a number of different chemicals

14. Classification of carcinogens • International Agency for Research on Cancer (IARC) • Classifies substances into 5 groups depending on strength of evidence for causing cancer • Group 1 Carcinogenic to humans • Group 2A Probably carcinogenic to humans • Group 2B Possibly carcinogenic to humans • Group 3 Not classifiable as to carcinogenicity to humans • Group 4 Probably not carcinogenic to humans

15. Classification of carcinogens • American Conference of Governmental and Industrial Hygienists (ACGIH) • Classifies substances into 5 groups depending on strength of evidence for causing cancer • Group A1 Confirmed human carcinogen • Group A2 Suspected human carcinogen • Group A3 Confirmed animal carcinogen with unknown relevance to humans • Group A4 Not classifiable as a human carcinogen • Group A5 Not suspected as a human carcinogen

16. Classification of carcinogens • Globally Harmonised System (GHS) of Classification of Labelling of Chemicals (see Section 11) • Beginning to be implemented in many countries • Includes regulatory requirements to identify carcinogens on labels

17. Sensitisation – (Allergic reaction) • The body’s immune system reacts as if the substance is an invading micro-organism, producing an adverse reaction • e.g. hay fever caused by pollen • White blood cells and antibodies play important roles in the body’s defence and immune systems • One type of antibody, Immunoglobulin E (IgE) is involved in many allergic responses • On first contact with an allergen, an allergy prone person makes large amounts of specific IgE antibodies • After first exposure these antibodies remain in the blood plasma for many years and respond rapidly to further exposure to that substance

18. Sensitisation – (Allergic reaction) • In industrial hygiene there are two main types of sensitisers - respiratory sensitisers and skin sensitisers • Sensitisation normally develops over a period of time following repeated exposure • Once sensitised, the immune system of a person is likely to respond adversely to subsequent exposure (even at very low levels)

19. Sensitisation – (Allergic reaction) • Skin sensitisers • Immune reaction results in release of histamine that causes inflammation of the skin (allergic contact dermatitis) • Symptoms include red, itchy, scaly rash • Usually occurs 6 – 48 hours after exposure • May also manifest as an itchy rash – pale raised areas surrounded by red skin – similar to nettle rash • Examples include chromium, nickel, latex and epoxy resins

20. Sensitisation – (Allergic reaction) • Respiratory sensitisers • Immune reaction results in histamine release causing a range of effects including narrowing and inflammation of airways and difficulty in breathing • Symptoms in many cases are characteristic of asthma • Term ‘occupational asthma’ often used instead of respiratory sensitisation • In extreme cases reaction can be particularly severe leading to heart stopping (anaphylactic shock) • Examples include isocyanates, grain and flour dusts, rosin-cored solder fumes, animal proteins, some wood dusts and detergent and bakery enzymes

21. Reproductive effects • Reproductive toxicants • Substance that may affect an individual by reducing their fertility • e.g. glycol ethers, lead • Developmental toxicants (teratogens) • Substances that may affect the developing foetus • May result in abnormalities of the child or affect its development after birth • e.g. lead, methyl mercury, thalidomide

22. Group work • In your allocated groups list 5 hazardous substances that people are exposed to at your workplaces. For each identified substance identify the following • What are the likely health effects of the substance? • e.g. irritant, asphyxiant, narcotic, carcinogenic etc • In what physical form are the substances present? • e.g. gas, vapour, fume, dust etc • Are the effects acute or chronic? • Are the effects local or systemic?