Toxic gases

Simple asphyxiants
Nitrogen
Methane
CO2
Chemical asphyxiants
Carbon monoxide (Co)
Hydrogen cyanide (HCN)
Hydrogen sulphide (H2S)
Systemically active gases
Arsine (Powerful hemolytic agent)
Stibene (Hemolytic agent)
Phosphine (Respiratory irritant & neurotoxic)
Irritant gases
Upper respiratory irritants: Highly soluble in water → dissolved in URT → irritation ”Ammonia (NH3) & SO2”
Lung tissue irritants: Less soluble in water → penetrate deep to lung tissue “Chlorine – Phosgene - Fluorine - NOx- O3

1. TOXIC GASES Dr. Dalia El- Shafei Assoc.Prof ., Community Medicine Department, Zagazig University http://www.slideshare.net/daliaelshafei

2. Carbon monoxide (Co) toxicity

3. Sources of incomplete combustion: Furnaces, boilers Internal combustion engine (warehouses, auto plants) Hazards increased in COLD weather with closed doors & windows.

4. At risk Occupations

5. Chronic exposure to CO NYC bridge & tunnel officers

6. Carbon monoxide  carboxyhemoglobin Binds to Hb more avidly than O 2 (200x) Shifts oxygen dissociation curve to “left”: Tissue anoxia Binds mitochondrial enzymes & myoglobin (50x) Increases platelet stickiness Deceases arrhythmia threshold

7. % COHb = % CO in air X Time X K

8. CO HALF LIFE

9. Toxicity Acute toxicity: depends on concentration of COHb in blood. <10% No symptoms At 10% Headache 10-20% Headache, tinnitus, dyspnea 20-30% As above + nausea, vomiting 30-45% As above + confusion, coma > 50% Respiratory center depression & death

10. Chronic toxicity

11. Dihalomethanes ” “ Methylene chloride & bromide ?

12. Solvent: degreasing, paint stripping Absorption through respiratory route or through skin Metabolized in bloodstream to …… CO Methylene Chloride (CH 2 Cl 2 )

13. May elevate COHb to 10% or more especially in poorly ventilated space Probably not significant to healthy person; may become mildly symptomatic Cigarette smokers, those with angina or current CHD a concern: excess CO may trigger symptoms Methylene Chloride

14. Methylene Chloride OSHA Standard: 25 ppm/ TWA 8 : STEL 125 ppm NIOSH: As low as can be achieved ( carcinogen ) Because of metabolic conversion to CO, the biological life of COHb from methylene chloride is longer than that from direct CO exposure !

15. Carbon monoxide: Exposure limits

16. Prevention & control Treatment Recommendation limits: TLV: CO in respirable air is 50 ppm & COHb in blood is 5g/100g Hb .

17. Hydrogen cyanide (HCN) & Hydrocyanic acid toxicity

18. HCN & Hydrocyanic acid toxicity Uses: 1- Fumigant (rodenticide, insecticide). 2- Extraction of silver & gold. Mechanism of action: - HCN absorbed through the lung. - Excreted in urine & feces as thiocyanates . - It inhibits cytochrome oxidase enzymes.

19. With a gold recovery rate of around 60-90%, its performance is superior to mercury with a recovery rate of 20-50%, depending on the processing system. Sometimes, cyanide is used to capture residual gold by leaching ore and tailings to which mercury has previously been added – i.e. mercury contaminated materials.

20. Toxicity .

21. Treatment

22. SEWER GAS Sewer gasis a combination of non-toxic and toxic gases that are present in sanitary and combined sewer collection systems at varying levels depending on the source. Elements of sewer gases include hydrogen sulfide, methane, ammonia, carbon dioxide, sulfur dioxide and nitrogen oxides, as well as biological organisms (bacteria, viruses, etc.). Other components in sewer gas may include substances that are improperly disposed of in sanitary sewer systems, such as gasoline or solvents.

23. “King of Poisons, Poison of Kings” Arsine poisoning

24. Industrial processes Semiconductor manufacturing (gallium arsenide) Fossil fuels Wood treated with arsenic preservatives Metallurgy Smelting (copper, zinc, lead) & refining of metals & ores Glass manufacturing Commercial products Wood preservatives Pesticides Herbicides Fungicides Food Seafood and fish Others Antiparasitic drugs Folk remedies