Human Exposure to Hydrogen Sulfide

Hydrogen Sulfide’s (H2S) main route in the human body is through inhalation and can potentially damage any of the body’s physiological systems: respiratory, cardiovascular neurological, ocular, metabolic, and the reproductive system. No known carcinogenic properties have been reported.

Respiratory Effects:

Through inhalation, exposure to hydrogen sulfide that is greater than or equal to 700 mg hydrogen sulfide/m3 can result in acute respiratory failure. The effects on the respiratory system are:

Non-cardiogenic pulmonary edema

  • the alveoli is where gas exchange between oxygen and carbon dioxide occur
  • hydrogen sulfide causes inflammation and compromises the alveoli, having the alveoli fill up with excess liquid from the capillaries, making gas exchange extremely difficult and inhibiting oxygenation for the body to function
  • untreated non-cardiogenic pulmonary edema will eventually cause hypoxia, low levels of oxygen in the blood
  • “non-cardiogenic” means the pulmonary (in relation to the lungs) edema is not related to heart failure

            Sore throat/ cough

  • Inflammation within the throat area causing coughing, sneezing, excess mucus production, hoarseness, lethargy

            Dyspnoea

  • Having difficulty breathing

Cardiovascular Effects:

            Chest pain

  • Pain and discomfort within the chest area

            Cardiac Arrhythmia

  • Having your heart beat abnormally
  • Electrical signals that control normal heart rate is compromised
  • Two types of arrhythmia: Tachycardia – heart is beating way too fast above normal; Bradycardia – heart is beating way too slow below normal

            Hypertension

  • High blood pressure that is approximately over 140/90 mmHg where normal is below 120/80 mmHg
  • Chronic hypertension can cause atherosclerosis (hardening of arterial walls), heart disease, kidney disease, stroke, damage to the eye
  • Victim may be asymptomatic (no physical symptoms are observable without running any medical tests)
  • Observable symptoms may include: headaches, shortness of breath, blurred vision, dizziness, nausea

Neurological Effects:

Neurological effects may be acute or chronic, having the potential to be permanent depending on the severity of exposure. Symptoms may include:

            Nausea

  • An uncomfortable feeling in the stomach that can cause vomiting

            Headaches

  • Pain and discomfort within the back of the head, upper neck, front of the head, or sides of the head

            Delirium

  • State of confusion and the inability to function psychologically

            Psychosis

  • It may include auditory or visual hallucinations, disorientation, paranoia, and anxiety

            Poor Memory

  • The inability to encode, retrieve, and recall certain past or recent events

            Neurobiological changes

  • Change in physiological functioning of the brain and can cause structural, behavioural, and personality changes

            Olfactory Paralysis

  • The loss of ability to distinguish between odours and perceive such odours

            Tremors

  • Involuntary movements of the muscles that can affect any part of the body
  • Abnormal electrical signals between neuron cells

            Convulsions

  • Involuntary contractions of the muscles; shaking uncontrollably

            Lethargy

  • extreme fatigue, feeling sleepy

            Insomnia

  • that ability of having trouble falling asleep or stay asleep in a normal cycle

            Ataxia

  • affects the cerebellum, coordination and the ability of movement is compromised

            Cerebral atrophy

  • The process of death and re-absorption of cells causing deterioration of brain cells, disrupting the physiological equilibrium of the cerebral system

Ocular Effects:

Depending on the level of exposure to the eye, a variety of symptoms may occur having extreme irritation to the eye as the most common symptom. Other symptoms may include:

            Photophobia

  • Having an extreme case of sensitivity towards light coming from any form of light source; can cause headaches, nausea and other symptoms

            Keratoconjunctivitis

  • Inflammation of the cornea and conjunctiva

            Blepharospasm

  • Muscle spasms that control the eyelid which causes uncontrollable blinking or complete inability to open the eye lids

            Lacrimation

  • Excess tears shed than normal

Metabolic Effects:

Hydrogen sulfide can impair the body’s metabolic system in relation to how the body uses oxygen to aid in physiological functioning. Impairment in the metabolic system can cause:

            Increased blood lactate concentration

  • Is an indicator of having the body going through shock
  • Associated with tachycardia, hypotension, cold and clammy skin

            Decrease in oxygen uptake

  • Can lead to hypoxia
  • Hydrogen sulfide can cause acidosis (decrease pH levels in the blood) which changes the structure of haemoglobin, inhibiting the protein from binding with oxygen within the capillaries of the alveoli, preventing oxygen distribution towards the entire body

            Decrease in skeletal muscle citrate synthase activity

  • Decrease activity within the aerobic and mitochondrial activity within cells, particularly the muscle cells
  • Can cause convulsions

            Switch from aerobic to anaerobic metabolism

  • Aerobic Metabolism – uses oxygen to convert nutrients such as carbohydrates, fats, and protein into ATP (adenosine triphosphate), a type of energy “currency” for the body
  • Anaerobic Metabolism – also known as glycolysis, is the process of producing ATP directly and only from carbohydrates without the use of oxygen; by-product is lactic acid – too high of a concentration of lactic acid will cause pain and discomfort

Reproductive Effects:

With many physiological abnormalities that hydrogen sulfide incurs in the body, it is reasonable that women who are pregnant have an increased risk of having an abortion/miscarriage due to the physiological irregularities. Defects and other abnormalities may also result in the fetus.