<P> Long - term, low - level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness . Chronic exposure to low level H 2S (around 2 ppm) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers, but the reports have not (as of circa 1995) been replicated . </P> <P> Short - term, high - level exposure can induce immediate collapse, with loss of breathing and a high probability of death . If death does not occur, high exposure to hydrogen sulfide can lead to cortical pseudolaminar necrosis, degeneration of the basal ganglia and cerebral edema . Although respiratory paralysis may be immediate, it can also be delayed up to 72 hours . </P> <Ul> <Li> 0.00047 ppm or 0.47 ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it . </Li> <Li> 10 ppm is the OSHA permissible exposure limit (PEL) (8 hour time - weighted average). </Li> <Li> 10--20 ppm is the borderline concentration for eye irritation . </Li> <Li> 20 ppm is the acceptable ceiling concentration established by OSHA . </Li> <Li> 50 ppm is the acceptable maximum peak above the ceiling concentration for an 8 - hour shift, with a maximum duration of 10 minutes . </Li> <Li> 50--100 ppm leads to eye damage . </Li> <Li> At 100--150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger . </Li> <Li> 320--530 ppm leads to pulmonary edema with the possibility of death . </Li> <Li> 530--1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing . </Li> <Li> 800 ppm is the lethal concentration for 50% of humans for 5 minutes' exposure (LC50). </Li> <Li> Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath . </Li> </Ul> <Li> 0.00047 ppm or 0.47 ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it . </Li>

What is the odor threshold for hydrogen sulfide