Toxic Gases I and II

Question 1

What are the 5 toxic gases we are covering?

Answer 1

Ammonia (NH3)
Hydrogen Sulfide (H2S)
Carbon Monoxide (CO)
Nitrogen Oxide gases
Sulfur Oxide gases
Other irritant gases, vapors, fumes, and dusts

Question 2

What are some of the properties of ammonia (NH3)

Answer 2

Soluble in water

Readily reacts with hydroxyl ions in moist mucous membranes to form ammonium hydroxide which is irritant and caustic

Question 3

What is the toxicity of ammonia?

Answer 3

Humans eyes burn at 25-35 ppm, but can detect 10 ppm in the air

Most frequently found in high conc in animal houses- enclosed confinement- 50 ppm during normal operation

Livestock most susceptible- swine and poultry

Exposure to 5000 ppm can cause acute death

Question 4

What is the MOA of ammonia?

Answer 4

Inhalation of large concentrations causes pulmonary edema, and lung congestion due to increased permeability to of lung capillaries

Decrease cell respiration

Death electrolyte and cellular metabolic effects- asphyxia

Question 5

What are diseases that cause respiratory insufficiency?

Answer 5

Inhaled irritants (hydrogen sulfide, nitrogen oxides, sulfur oxides, fumes, dusts, vapors)
OP
Polychlorinated biphenyls
Cardiac glycosides

Question 6

What are some of the properties of hydrogen sulfide (H2S)?

Answer 6

Odor of rotten eggs
Water soluble
Irritant bc converted to sulfuric acid in soln and forms sodium sulfide on contact with moist MM
Sulfide with silver, iron, lead and other metals to form black or dark colored compounds in GIT and tissues

Question 7

How are animals exposed?

Answer 7

H2S, NH3, CO2 and methane are liberated from the decomposition of urine and feces in underfloor waste pits, deep litter, manure packs, sewage, and other organic matter containing sulfur

Question 8

What is the normal level of H2S? Deadly level?

Answer 8

10 ppm

May reach 1000 ppm

Question 9

True or False. H2S is the most dangerous sewage gas.

Answer 9

True.

Question 10

What are some of the toxicity levels associated with H2S?

Answer 10

Humans can detect in air 0.025 ppm
200 ppm- olfactory accommodation - DANGER
Sudden exposure to 400 ppm may be FATAL
1000 ppm causes RAPID UNCONSCIOUSNESS and DEATH IN 1 HR
>2000 ppm RESPIRATORY PARALYSIS AFTER 1-2 BREATHS

Question 11

What is the acute toxic level in mammals?

Answer 11

~500-800 ppm

Question 12

What is H2S converted to in the blood?

Answer 12

Alkali sulfide

Question 13

What is the MOA of H2S?

Answer 13

Inhibition of cell respiration- decreased cytochrome oxidase

Question 14

What is the treatment for H2S toxicosis?

Answer 14

Sodium Nitrite IV may be particularly effective by forming methemoglobin– binds sulfide radicals and reactivates cytochrome oxidase

Question 15

What is the most effective treatment?

Answer 15

Prevention– use H2S monitors!

While manure pit injuries are rare, they are highly deadly

Question 16

What are some of the properties of carbon monoxide?

Answer 16

Odorless, colorless, NOT WATER SOLUBLE

Question 17

What is the toxicity level?

Answer 17

> 1000 ppm (0.1%) can cause clinical signs and death with 1 hour of exposure

Question 18

What is the MOA?

Answer 18

CO combines with hemoglobin to form carboxyhemoglobin (COHb) which cannot carry O2
(Hb affinity for CO is 240x greater than for )2)

Carboxyhemoglobin interferes with release of O2 carried by normal hemoglobin

Death is from hypoxia

Question 19

What are some of the lesions associated with CO toxicity?

Answer 19

Blood is bight red and the MM are a healthy pink (bc carboxyhemoglobin is bright red and due to hyperventilation)– won’t always see this

Question 20

What are some of the properties of nitrogen oxide gas?

Answer 20

Reddish brown (NO2)
Colorless (N2O4)
Mixture of the two gases is yellow or yellow-brown haze
Forms layers on top of silage and settles down the chute
Chlorine like odor
Low solubility in water- the gases form nitric acid (HNO3) and nitric oxide (NO)

Question 21

What is the source of exposure?

Answer 21

Nitrogen Oxide poisoning- called “silo filler’s dz”

Nitrogen Dioxide (NO2) is a major pollutant (burning of fossil fuels), not to be confused with nitrous oxide (N2O) which is an anesthetic

Question 22

What is the toxicity of nitrogen oxide gases?

Answer 22

50-150 ppm causes mild to moderate irritation of the eyes and upper respiratory mucosa

Acute exposure to high concentrations is MORE toxic than chronic exposure to low concentrations

Question 23

What are the toxicokinetics of nitrogen oxide gases?

Answer 23

NO2 and N2O4 gases form nitric acid upon contact with MM

The acid or gases may cross respiratory mucosa and cause cellular damage in the lungs- pulmonary edema

Question 24

What is the MOA?

Answer 24

Direct irritation of the MM by nitric acid
Bc they are soluble they can pass via the upper to lower respiratory tract and cause damage in the lungs (bronchi/alveoli)
Lung damage- due to caustic reaction with polyunsaturated fatty acids at cell membrane– this leads to pulmonary edema, hemorrhage
Death is from hypoxia- RESPIRATORY FAILURE

Question 25

What are some of the lesions associated with nitrogen oxide gases?

Answer 25

Cyanosis Methemoglobinemia Necrosis of skeletal muscles

Question 26

What are the treatments?

Answer 26

Diuretics- if pulmonary edema Methylene Blue IV- methemoglobinemia Ointments (antibiotic) for MM

Question 27

What are the sources of sulfur oxide gases?

Answer 27

``` Sulfur dioxide (SO2) and sulfur trioxide (SO3) are industrial pollutants Fossil fuel combustion at power plants (73%) ```

Question 28

What are some properties of sulfur oxide gases?

Answer 28

Highly soluble in water | Sharply irritant to MM because of the form sulfurous and sulfuric acids on contact with water

Question 29

What is the MOA?

Answer 29

Direct irritation of the MM and reflex bronchoconstriction | Death due to hypoxia

Question 30

What are most fire-related deaths the result of?

Answer 30

80% are from smoke inhalation and not from the burns

Question 31

True or False. The LD50 of smoke is 9.4.

Answer 31

False. There is no LD50 bc smoke is a heterogenous mixture of gases.

Question 32

What is the MOA of a simple asphyxiant? Chemical asphyxiant? Irritant?

Answer 32

Simple- inert CO2 gases or vapors that displace O2 Chemical- prevent uptake of )2 Irritants- chemically reactive on contact with MM

Question 33

What are 3 examples of simple asphyxiant?

Answer 33

CO2 Methane Oxygen-deprived environment

Question 34

What are examples of chemical asphyxiant?

Answer 34

CO- this is the most serious systemic agent with smoke inhalation-- CHANGES O2 CARRYING CAPACITY OF Hb Hydrogen cyanide Hydrogen sulfide Nitrogen oxides

Question 35

What should you not use to treat smoke inhalation and why?

Answer 35

STEROIDS- higher mortality and infection rates

Question 36

In order to treat, how long should you monitor the patient? And when should you recheck?

Answer 36

Monitor 6-8 hours post-exposure | Recheck in 72 hours

Question 37

What are the 3 high water solubility irritants (upper airway injury)?

Answer 37

Acrolein (aldehyde) Sulfur Dioxide Ammonia

Question 38

What are the two intermediate water solubility irritants (upper and lower airway injury)?

Answer 38

Chlorine | Isocyanates

Question 39

What are the 2 poor water solubility irritants (pulmonary parenchymal injury- alveoli, alveolar ducts?)

Answer 39

Phosgene (plasticizer) | Nitrogen oxides

Question 40

What is the mechanism of soot?

Answer 40

Binds to the respiratory mucosa allowing other material to adhere and react Sulfur Dioxide adhere highly to soot

Question 41

What is the most important at determinant of respiratory injury?

Answer 41

Solubility

Question 42

Highly soluble particles affect which part of the respiratory system? Low water soluble products?

Answer 42

High- Upper airway | Low- lung, bronchiole, and alveoli