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Chronic Effects of Hydrogen Sulfide Exposure

Hydrogen sulfide is a colorless, highly flammable gas with a strong odor reminiscent of rotten eggs. It occurs naturally in hot springs, volcanic gas, crude petroleum and sometimes in underground well water due to the degradation of sulfates in non-organic matter in a process known as anaerobic digestion, meaning without the presence of oxygen. Since this compound has several industrial applications, the chronic effects of hydrogen sulfide exposure have been examined.

  1. Respiratory Effects

    • According to the Agency for Toxic Substances and Disease Registry (ATSDR) in Georgia, hydrogen sulfide is readily absorbed through the lungs, which is the primary route of exposure. After acute exposure through inhalation, hydrogen sulfide particles bond with the iron (hemoglobin) present in the mitochondria membrane of red blood cells. This has the effect of blocking the utilization of oxygen, which prevents cellular respiration from taking place. In short, this means that anaerobic metabolism is blocked and cells cannot produce energy. Although hydrogen sulfide does not accumulate in the body, the immediate respiratory effects of even moderate exposure levels and repeated disruption of cellular respiration does cause an accumulation of lactic acid in the body. Overall, the chronic effects of hydrogen sulfide exposure to the lungs contribute to bronchitis, fluid retention in the lungs, bronchial hemorrhage and even respiratory arrest.

    Systemic Toxicity

    • Since hydrogen sulfide interrupts cellular metabolism, it is considered a broad-spectrum mitochondrial poison that acts similar to cyanide to produce general systemic effects, according to toxicologist Jack Thrasher, PhD. As Dr. Thrasher notes in his report, “Toxicology of Hydrogen Sulfide,” the Illinois Institute For Environmental Quality conducted a comprehensive review of the literature on the known effects of hydrogen sulfide exposure and summarized that varying levels of exposure have been known to produce headaches, nausea, insomnia, depression, loss of appetite and visual disturbances. Impairment of the corneal reflex has also been reported, which means that the ability to automatically blink may be lost, or that the eyelids may close involuntarily.

    Reproductive Effects

    • According to ATSDR, there is sufficient evidence to suspect that exposure to hydrogen sulfide may increase the risk of spontaneous abortion, or miscarriage. While there is no information available about the potential for defects in fetal development in humans, studies based on animal models indicate that hydrogen sulfide may behave as a neurotoxicant and negatively affect fetal development. It is not known at this time if hydrogen sulfide can be passed to infants in breast milk in either animals or humans.

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