The document discusses various topics related to toxicology including: - Absorption, distribution, metabolism and excretion of chemicals in the body - Factors that affect absorption such as routes of entry and chemical properties - Threshold doses and variability in individual susceptibility - Acute and chronic effects of toxins - Carcinogens and mutagens and their classification - Dose-response relationships and metrics like LD50 - Toxicity testing methods including the Ames test

1. Mike Slater Diamond Environmental Ltd

2. "All substances are poisons ; there is none which is not a poison. The right dose differentiates a poison from a remedy"

3. Chemicals Organic Inorganic

4. Homeostasis Chemical reactions which maintain very stable body chemistry against a background of constant environmental change

5. Inhalation Skin contact Ingestion

8. Absorption Absorbed dose is generally a fraction of exposure dose Toxicant must be able to cross cell membranes

9. Factors Affecting Absorption Degree of exposure Routes of entry Properties of chemical

10. Absorption Through the Lungs Amount of air inhaled Gases Aerosols

12. Particle Deposition Interception Impaction Sedimentation Diffusion

13. V t = terminal velocity g = acceleration due to gravity d = diameter of particle p p = density of particle p m = density of medium µ = viscosity of medium

14. Particle Deposition Falling speed is proportional to the density of the particle the square of its diameter

15. Aerodynamic Diameter The diameter of a sphere of unit density (i.e. a water droplet) that has the same falling speed as the real particle

18. Absorption Through Skin Absorption depends on lipid solubility Uptake greater if skin damaged Uptake varies

19. Absorption Through Skin Many organic compounds readily absorbed solvents pesticides organo-metal compounds

20. Absorption Through Gut Better absorption with un-ionised, fat soluble substances

21. Absorption Through Gut Stomach Acidic Acidic compounds absorbed

22. Absorption Through Gut Intestine Alkaline Alkaline compounds absorbed

23. Distribution Transport by blood Rate Substances released from storage

24. Storage Fat lipophilic compounds e.g. some pesticides (DDT), dioxins, PCBs Bones chemicals similar to calcium fluorine, lead, strontium Blood Liver and kidney Other organs / tissues

25. Biotransformation Occurs mainly in liver Also in lungs, kidney & intestine

26. Biotransformation Catalysed by enzymes including Cytochrome P450

27. Biotransformation Increases water solubility for excretion via kidney

28. Biotransformation Metabolites or intermediaries can be toxic

29. Phase I reactions Oxidation Reduction hydrolysis Phase II reactions Conjugation Synthesis Metabolites Elimination

30. Metabolites - Some Examples Substance Metabolite Benzene Phenol Dichloromethane Carbon monoxide N-hexane 2, 5 hexanedione Methanol Formaldehyde Styrene Mandelic acid Phenylglyoxylic acid Toluene Hippuric acid o- cresol Trichloroethylene Trichloroacetic acid Trichloroethanol Xylene Methyl-hippuric acid

31. Biotransformation Sometimes biotransformation increases toxicity

32. Biotransformation Examples Benzene n-hexane Methanol Dichloromethane carbon monoxide formed

33. Excretion Kidney urine water soluble compounds

34. Excretion Lungs volatile compounds gaseous metabolites

35. Excretion Liver bile fat soluble compounds

36. Excretion Other routes Hair Nails Skin Sweat Milk

37. Excretion - the Kidneys Filters the blood of its small molecules and ions and then ...

38. Excretion - the Kidneys Reclaims useful materials

39. Excretion - the Kidneys Surplus or waste molecules and ions flow out as urine

40. Biological Half Life Time taken for half the amount of the substance absorbed to be excreted

42. Some Half Lives Toluene ~ 10 hours Selenium ~ 10 days Mercury ~ 6 weeks Cadmium ~ 10 years or more

43. Half Lives Mineral dusts Metal compounds Organic solvents & inorganic gases Amphibole asbestos is particularly biopersistent Can remain in lungs for decades

47. Threshold Dose

48. Threshold Dose The point at which toxicity first appears NOAEL "no observed adverse effect level"

49. Susceptibility Variation in susceptibility between individuals Different doses required to produce same effect

50. Susceptibility Most susceptible groups include Elderly, Children, People with pre-existing disease Inter-species variation

54. Stochastic Effects Probabilistic Increasing probability of effect with increasing dose e.g. carcinogens

58. Types of Effect Local at point of contact with the body Systemic following distribution

59. Types of Effect chronic sub-chronic sub-acute acute timescale

60. Exposure and Effect Acute < 24hr usually 1 exposure Subacute 1 month repeated doses Subchronic 1-3 months repeated doses Chronic > 3months repeated doses

61. Harmful Effects Asphyxiant Irritant Corrosive Narcotic Sensitiser Toxic Carcinogen Mutagen Teratogen

62. Simple Asphyxiants Inert gases Reduce oxygen concentration in air e.g. nitrogen, argon

63. Oxygen Level Effect 21% Normal atmospheric concentration 18% Minimum “acceptable” concentration 17% Breathing faster & deeper 16.25% Flame safety lamp will extinguish 15% Dizziness, buzzing noise, rapid pulse, headache, blurred vision 9% Unconsciousness 6% Breathing stops, cardiac arrest

64. Chemical Asphyxiants Interference with oxygen transport, or utilisation of oxygen

65. Chemical Asphyxiants Carbon monoxide carboxyhaemoglobin

66. Chemical Asphyxiants Methaemoglobin oxidation of haemoglobin Fe2+ to Fe3+ Aniline Nitrobenzene Nitrites

67. Chemical Asphyxiants Haemolytic agents destroy blood cells arsine, stibene

68. Chemical Asphyxiants Inhibition of cellular respiration cyanide hydrogen sulphide

69. Causes local inflammation of tissue

70. Destroys tissue

71. Depresses Central Nervous System Causes dizziness, nausea, drowsiness

72. Causes an allergic reaction in susceptible people

73. Sensitisers Cause allergic reaction in susceptible individuals Cannot identify susceptible individuals! Usually develops gradually Not always easy to identify causative agent

74. Sensitisers – CHIP Classifications R42 May cause sensitisation by inhalation R43 May cause sensitisation by skin contact

75. Sensitisers Respiratory Rhinitis Asthma Allergic alveolitis

76. Source: http://www.hse.gov.uk/statistics/causdis/asthma.htm

77. Source: http://www.hse.gov.uk/statistics/causdis/asthma.htm

78. Sensitisers Skin Allergic contact dermatitis

79. Skin Allergens Nickel salts Chromium VI compounds Epoxy resins Latex

80. Stops body functioning normally

81. Classification depends on dose required to cause effect

82. Toxic hazards Carcinogens cause cancer Mutagens cause genetic damage Reproductive Hazards Teratogens harm the unborn child

83. Cancer Unregulated growth and proliferation of cells

84. Cancer Benign tumours Malignant tumours

85. Carcinogens Direct acting or metabolites

86. Carcinogens Long latency period

88. Carcinogens Metastasis

89. Occupational Cancer HSE estimates 4% of all cancers 6,000 deaths every year

90. Carcinogens - CHIP Classification Category 1 Substances known to be carcinogenic in humans R45 May cause cancer Category 2 Evidence of cancer from animal studies R45 May cause cancer Category 3 Suspect carcinogens R40 Limited evidence of a carcinogenic effect

91. Carcinogens – Some Examples Category 1 Arsenic Asbestos Benzene Benzidine Vinyl chloride monomer R45 May cause cancer Category 2 Beryllium Cadmium oxide Strontium chromate Trichloroethylene R45 May cause cancer Category 3 Chloroform Formaldehyde Hydroquinnone Lead chromate R40 Limited evidence of a carcinogenic effect

92. IARC Classification Group 1 Known human carcinogen Group 2A Probable human carcinogen Group 2B Possible human carcinogen Group 3 Not classifiable for human carcinogenicity Group 4 Probably not carcinogenic to humans

93. COSHH Schedule 1 Examples of other substances and processes to which definition of “carcinogen” applies

94. COSHH Schedule 1 Coal soots, coal tar, pitch, coal tar fumes Hardwood dusts Leather dust in boot and shoe manufacturing Rubber process dust and fume Used engine oils

95. Mutagens Most mutagens also carcinogens Not always the case e.g. Vanadium pentoxide (not carcinogenic)

96. Mutagens - CHIP Classification Category 1 Substances known to be mutagenic in humans R46 May heritable genetic damage Category 2 Evidence from animal or in-vitro studies R46 May heritable genetic damage Category 3 Suspected mutagens R68 Possible risk of irreversible effects

97. Mutagens - CHIP Classification Category 1 R46 May heritable genetic damage Category 2 Butadiene Benzene Sodium chromate R46 May heritable genetic damage Category 3 Aniline Trichloroethylene Vaadium pentoxide R68 Possible risk of irreversible effects

98. Mixed Exposures Independent effects Interactions

99. Interactions Additive Antagonistic Synergistic Potentiation

100. Interactions - Independent No interaction

101. Interactions - Additive The combined effect is equal to the individual sum of the effects Example – Narcotics, usually same target organ same mechanism

102. Interactions - Synergistic Combined effect is greater than sum of individuals e.g. Ethanol & Carbon tetrachloride

103. Asbestos and lung cancer (Lung cancer death rates per 100 000 person years) Asbestos worker Smoker Death rate Mortality rate No No 11.3 1 Yes No 58.4 X 5 No Yes 122.8 X 11 Yes Yes 601.6 X 53

104. Interactions - Potentiation Substance increases the effect of a hazardous substance e.g. Isopropanol & carbon tetrachloride, barbiturates and solvents

105. Interactions - Antagonistic Substance reduces effect of another substance Cd & Zn – less kidney damage

107. Median Lethal Dose - LD50 The dose which will kill 50% of a test population

109. Some LD50s ETHYL ALCOHOL 7060 SODIUM CHLORIDE 3000 NAPHTHALENE 1760 FERROUS SULFATE 1500 ASPIRIN 1000 FORMALDEHYDE 800 AMMONIA 350 CAFFEINE 192 PHENOBARBITAL 150 CHLORPHENIRAMINE MALEATE 118 DDT 100 STRYCHNINE SULFATE 2 NICOTINE 1 DIOXIN 0.0001 BOTULINUS TOXIN 0.00001 mg/kg body weight

110. Plot the dose-response curve for the following data dose No. of deaths Group size % deaths 5 0 20 0 10 0 20 0 25 3 20 15 50 7 20 35 100 15 20 75 250 19 20 95 500 20 20 100 1000 20 20 100

111. Dose response curve for previous data

114. NOAEL LD50

115. Toxicity Testing LD50 LDLo LC50 LCLo TD50 TDLo TC50 TCLo

116. Hodge-Sterner Table LD50 Toxicity degree Probable lethal dose <1.0 mg/kg Dangerously Toxic A taste 1-50 mg/kg Seriously Toxic A teaspoon 50-500 mg/kg Highly Toxic An ounce 0.5- 5gm/kg Moderately Toxic A pint 5- 15gm/kg Slightly Toxic A quart >15gm/kg Extremely low Toxicity More than a quart

118. Some LD50s ETHYL ALCOHOL 7060 SODIUM CHLORIDE 3000 NAPHTHALENE 1760 FERROUS SULPHATE 1500 ASPIRIN 1000 FORMALDEHYDE 800 AMMONIA 350 CAFFEINE 192 PHENOBARBITAL 150 CHLORPHENIRAMINE MALEATE 118 DDT 100 STRYCHNINE SULPHATE 2 NICOTINE 1 DIOXIN 0.0001 BOTULINUS TOXIN 0.00001

121. Toxicological studies are normally carried out over a short timescale.

122. What are the implications of this?

123. Skin Irritation Draize test Also used for eye irritation

124. Ames Test Reverse mutagen test

125. Ames Test 90% of known carcinogens are mutagenic in the Ames test

126. Ames Test Reverse mutation

127. Ames Test Mutant strain of bacterium Salmonella typhimurium

128. Ames Test Reverse mutation caused by mutagen results in bacteria which can make histidine growth of colonies on test plate

129. Ames Test Some compounds are not mutagenic until metabolised Ames test can include liver enzymes

131. Median Lethal Dose - LD50 Must specify Species Route of exposure Dose per kg body weight