This document discusses carbon monoxide (CO) poisoning, including its sources, mechanisms of action, effects, diagnosis, and treatment. Some key points: - CO is an odorless, colorless gas produced by incomplete combustion of carbon-containing substances. It is widely encountered in industry. - CO poisoning occurs through CO binding to hemoglobin in red blood cells, preventing oxygen transport. It can also directly impact mitochondria and other heme proteins. - Effects of CO poisoning range from headaches and nausea at low levels to confusion, loss of consciousness, and death at high levels. Late neurological and psychiatric effects are also possible. - Diagnosis is made through measuring COHb levels in blood. Treatment

1. Chemical Agents
Dr S K Haldar

2. Chemical
Agents
Dust
Organic e.g.
Sugarcane, Hey
Inorganic e.g.
Silica, Coal,
Asbestos
Gases
Irritants
Site of Action
Local/ Primary
Systemic/
Secondary
Solubility
Water Soluble
(Readily)
Water Insoluble
(Slightly
Soluble)
Asphyxiants
(Heart of Total
Hazards)
Simple e.g. CO2,
Methane,
Hydrogen, Aniline
Chemical e.g.
CO, H2S, HCN
Drug like
Anesthetic e.g.
Ether
Solvents e.g.
Chloroform,
Benzene, Toluene
Hydrocarbon
Metals &
their Fumes
Solvents Chemicals
Acids, Alkalis,
Organic

3. GASES - Carbon Monoxide (CO)
TWA 8Hrs. - Time weighted average
= 50ppm TLV (Threshold limit value)
= 58 mg/M³
Characteristics:- Colourless, Odourless, non-irritant
gas, which is slightly soluble in water & burns in
air with bright blue red flame. It is the most
widely encountered toxic gas in industry,
commonly resulting from incomplete combustion
of Carbonious Material.

4. Threshold limit value
The TLV for chemical substances is defined as a concentration in air, typically for
inhalation or skin exposure. Its units are in parts per million (ppm) for gases and in
milligrams per cubic meter (mg/m³) for particulates such as dust, smoke and mist.
[1ppm = (mg/m^3) * 24.45 / molecular weight] This formula is not applicable to
airborne particles.
Three types of TLVs for chemical substances are defined:
1. Threshold limit value - Time weighted average (TLV-TWA): average exposure on the
basis of a 8h/day, 40h/week work schedule
2. Threshold limit value - Short-term exposure limit (TLV-STEL): spot exposure for a
duration of 15 minutes, that cannot be repeated more than 4 times per day with at
least 60 minutes between exposure periods
3. Threshold limit value - Ceiling limit (TLV-C): absolute exposure limit that should not
be exceeded at any time
TLVs for physical agents include those for noise exposure, vibration, ionizing and non-
ionizing radiation exposure and heat and cold stress.

5. CO By-product
Most common operations of
1) Blast Furnace Gas:- 20-25% CO.
2) Coal & Coke Oven Gas:- 7-16% CO.
3) Petrol & LPG:- 1-10% CO.
4) Diesel Engine Exhaust:- 0.1-0.5% CO.

6. Mechanism of Action:-
1. It is a chronic Asphyxiant, because it combines with Hb, with an
affinity 200-300 times more than that of Oxygen, to form Carboxy
Haemoglobin COHb. CO also increases the Oxygen affinity of HB &
causes the O₂ Dissociation Curve to shift to Left, by impending the
release of O₂ to the tissues.
2. CO exerts a direct action by combining when other Haem containing
Protein in the cells like Cytochrome Oxydase, Myoglobin,
Cytochrome P₄₅₀.
3. Interaction with Cytochrome Oxydase results in Mitochondrial
Dysfunction & if it prolongs, impairment of Oxidative Mechanism.
4. Alternative Hypothesis:- CO damages Mitochondria by provoking
the release of free Nitric Oxide.
5. CNS Injury may also be due to Re-oxygenation injury as a result of
production of potentially reduced Oxygen Spaces (Radicals), which in
turn can oxidize Essential Proteins & Nucleic Acids & induce Brain
Lipid Paroxydation.

7. Blood CO Levels:-
1) Normal Subject:- Less than 1%
2) Occasional Smokers:- 5-6%
3) Heavy Smokers:- More than 10%
Detection of CO in Air:- Previously they used to use
Detector Tube. In Detector Tube the colour
changes & gives indication of CO Concentration.
Now a days Electronic CO detectors, Dedicated CO
Detectors are available.

8. How to Calculate Atmospheric CO Exposure:-
Atmospheric CO Exposure % of COHb
= K X % CO in Air X Minutes of Exposure
Here K is a Constant = 3 for an individual at rest
5 for Sedentary Action
8 for Light Job
11 for Heavy Job.
A less unknown hazard arises from the use of Methylene
Chloride (Dichloro Methane), a widely used solvent, used in
paint & warmish removal. Methylene Chloride is readily
absorbed through Skin & Lungs, & Metabolized in Liver. CO
is an important metabolite of Methylene Chloride & forms
COHb. So it is Entoxification in the body.

9. Clinical Features of CO Toxicity:-
Cherry Red Colour of Face & Skin:- “When You are Red You are Dead” .
% of COHb Effects
1 2.5-4 % Decreased Short Term Maximal Exercise Duration in
young healthy person.
2 Up to 5.1 % Decrease Exercise Duration further & there will be
Chest Pain on Exertion, in patients with IHD.
3 Up to 20 % Equivocal Effects on Visual Perception. Motor &
Sensory Motor Performance & Neuro behavioural
Changes.
4 Up to 33 % 1) Decreased Oxygen Consumption with short term
strenuous exercise.
2) Throbbing Headache.
5 Up to 50 % Dizziness, Nausea, Weakness & Collapse.
6 More than 50 % Unconscious & Death.

10. Diagnosis:-
1) Biochemical:-
a) COHb level in Heparinized Blood Sample measured by
CO_Oxymetere or by Spectrometer.
b) In Post Mortem by blood Gas Chromatographic Analysis is
a preferred method, because of breakdown of Hb after death.
2) Clinically:-
There is no diagnostic symptom complex. So the diagnosis is
missed easily. The Clinical Presentation may vary widely with
Vomiting, Headache, Malaise, Weakness, Fatigue, Chest Pain,
Palpitation, Dyspnoea etc.
Without adequate treatment 10 – 30% patients with severe toxicity
may develop late neuro psychiatric manifestations within 3 to 240
days after exposure.

11. Treatment of Acute Effect:-
Without treatment Half life of CO is 4 Hours.
1) 100% Oxygen
2) Hyperbaric Oxygen at 2.5 Atm or more
pressure:- [Normal Atmospheric Pressure is 100 KPa.
Hyperbaric is given at 252 KPa. The patient might
rupture Alveoli or Tympanic Membrane. Hyperbaric
Oxygen Therapy at 2.5 ATM Pressure Reduces the Half
Life of COHb to 20 minutes. It also increases the
amount of Oxygen dissolved in the blood to a
concentration sufficient to meet the needs of the body,
even without functioning haemoglobin percentage. It
is sufficient to meet the tissue need of oxygen.]

12. Conditions for Hyperbaric Oxygen Therapy:-
1) Pregnant Woman
2) History of Unconsciousness.
3) Neurological & Psychiatric Symptoms.
4) If there are Cardiac Complications.
5) COHb is above 10%. Now a days in most of
the Western Countries and Australia they start
Hyperbaric treatment at COHb level above
25%.

13. Late Effects:-
They are due to
1) release of CO that was attached to Myoglobin and
2) Permanent CNS Damage
A) Neuro Psychiatric Symptoms
B) Cardiovascular System
C) Reproductive System

14. A) Neuro Psychiatric Symptoms:-
They may develop 2-3 weeks after.
1) Parkinsonism.
2) Visual Impairment.
3) Personality Changes:- Seen in 30% of cases
like Irritability, Verbal Impairment, Verbal
Aggressiveness, Violence, Impulsiveness,
Moodiness.
4) Memory Impairment in 40% Cases.
5) Depression & Suicidal Thoughts.

15. Mechanism of Neuro Psychiatric Symptoms:-
Symptoms are mainly due to Anoxia and Specific
Cytotoxic action of CO. That causes Necrosis of
Globus Pallidus. It is a common lesion and may
also be seen in Basal Ganglia, Hippocampus &
White Matters.
Diagnostic Tests for Neuro Psychiatric Symptoms:-
1) MRI
2) CAT (Computerized Axial Tomography) Scan
3) PET (Positron Emission Tomography) Scan.

16. B) Cardiovascular System:-
Angina Pectoris
ECG Changes after Light or Moderate Exercise.
C) Reproductive System:-
1) Low Birth Weight Babies to Pregnant Woman.
2) IUFD:- Intra Uterine Foetal Death.
3) Neurological abnormalities in Live Births.