Health effects of H 2 S

Transcription

1 Health effects of H 2 S Karin Pacheco, MD, MSPH Division of Environmental and Occupational Health Sciences

2 Disclosures Karin Pacheco Nothing to disclose

3 Toxic Gas at Casey: Correcting Misinformation * Dr. Karin Pacheco says the building is safe! Did you know that last spring Dr. Pacheco sent a letter to the Casey community saying that the building is safe because the hydrogen sulfide levels were far below the OSHA limits of 10,000 parts-per-billion (ppb)*? The E.P.A. puts safe hydrogen sulfide limits for children at just 1.43 ppb. *10 ppm

4 Where did this suggested level come from? The daily inhalation exposure to the human population that is likely to be without an appreciable risk of any deleterious effects during a lifetime, the RfC, has been determined to be mg/m3 or 1.4 ppb. Based on an inhalation study in lab rats by Brenneman et al. (2000) that found olfactory nasal tract lesions in rats exposed to 30 or 80 ppm H 2 S (6h/d, 7d/wk, 10 wks) but not at 10 ppm (14 mg/m3), the NOAEL. Then divided by 300 to account for species variability, and sub-chronic exposure > 1.4 ppb.

5 The study itself listed: H 2 S Levels Lowest observed adverse effect level (LOAEL) 42 mg/m3 = 30 ppm No observed adverse effect level (NOAEL) 14 mg/m3 = 10 ppm Average ambient concentrations (ATSDR 10/2014): From natural sources: 0.11 and 0.33 ppb. In urban areas <1 ppb. Levels > 90 ppb near natural sources of hydrogen sulfide or near industries releasing hydrogen sulfide.

6 What about human production? Most endogenous production results from the break down of sulfhydryl-containing amino acids (e.g., cysteine) by bacteria in the intestinal tract and the mouth; it is also produced via enzymatic pathways. In the mouth: H 2 S is a component of bad breath: from ppb have been measured in mouth air. In the large intestine: H 2 S is generated by bacteria and can compose up to 10% of intestinal gases. In flatus, H 2 S mean values are 1-4 ppm, high of 18 ppm. Hydrogen Sulfide - ToxFAQs ATSDR

7 What function does H2S serve? H 2 S is a gaseous messenger molecules (gasotransmitters); NO and CO are the others. H 2 S functions: Necessary to sense oxygen levels in the carotid body Protects against development of Alzheimer s disease Protects against vascular scarring from heart attacks Individual variability in the odor threshold for H 2 S : from ppm (0.5 ppb) to 0.3 ppm (300 ppb).

8 Therapeutic gases for the treatment of ischemia. Ischemia and reperfusion from mechanism to translation Holger K Eltzschig & Tobias Eckle Nature Medicine 2011; 17: Human production of H 2 S by enzymatic pathways

9 Human effects of H 2 S Respiratory: (low concentrations) Irritation to eyes, nose throat Difficulty breathing for some asthmatics Nervous system: Headaches, poor memory, tiredness, balance problems Are there long-term health effects? Hydrogen Sulfide - ToxFAQs ATSDR

10 What about natural experiments? Chronic Ambient H 2 S Exposure & Cognitive Function N=1,637 adults ages from Rotorua City, New Zealand, chronic H2S exposure from geothermal source Exposure from monitoring networks, calculated for last 30 years: from 0 64 ppb. Measured neuropsychological tests (memory, attention, fine motor skills, psychomotor speed and mood) Found no association, but higher quartiles of exposure associated with faster response times, & digit symbol. Reed BR, Crane J, Garrett N, Woods DL, Bates MN. Neurotoxicol Teratol 2014;42:68-76.

11 What about natural experiments? Investigation of H 2 S exposure and lung function, asthma, & COPD in a geothermal area of New Zealand N=1,204 adults ages H 2 S exposure calculated for current, last 30 yrs, TWA and peak exposures: 0-58 ppb. Measured association of spirometry, smoking, COPD, asthma with H 2 S exposure quartiles. No lung function, COPD or asthma, from recent or long-term H 2 S exposures. Suggested improved spirometry & higher current H 2 S. Bates MN, Crane J, Balmes JR, Garrett N. PLOS One March 30, 2015.

12 Summary H 2 S is an irritant, and can cause short-term respiratory and neurological symptoms, similar to those reported in the school. Natural experiments in cities with constant H 2 S exposures 0 64 ppb did not show long-term effects on lung function or cognitive function.