Brain Damage Caused by Hydrogen Sulfide: A Follow-Up Study of Six Patients
by Bjarrn Tvedt, MA, Knut Skyberg, MD, Olaf Aaserud, MD, Anund Hobbesland, MD, and Tove Mathiesen, MA

Published in the American Journal of Industrial Medicine

Abstract

Hydrogen sulfide (H2S) poisoning involves a risk of hypoxic brain damage. Six patients who lost consciousness due to H2S poisoning are described. The symptoms varied from anosmia in the patient with the shortest but highest exposure to delayed neurological deterioration in the patient with the longest exposure. The two patients with the most serious symptoms developed pulmonary edema, which may have prolonged the hypoxia. The patients were reexaminated 5 years or more after the poisoning. The five patients who had been unconscious in H2S atmosphere for from 5 to 15-20 min showed persisting impairment at neurological and neuropsychological re-examination. Memory and motor function were most affected. One patient was seriously demented. Recent reports of large groups of H2S-poisoned workers probably underestimate the risk of sequelae, due to the inclusion of cases with exposure of short duration and lack of follow-up.

…..
Above abstract available from the US National Library of Medicine, National Institute of Health:  http://www.ncbi.nlm.nih.gov/pubmed/1867221.

Full document available from the California State University website:  http://www.csun.edu/~dorsogna/byron/H2Snew.pdf.

Published by the Massachusetts Department of Environmental Protection (http://www.mass.gov/dep/recycle)

…..

Hydrogen Sulfide and Sulfides:
Sulfides are naturally occurring gasses that often give a landfill gas mixture its rotten egg smell. Sulfides
can cause unpleasant odors even at very low concentrations. Hydrogen sulfide is a colorless, flammable
gas and is one of the most common sulfides responsible for landfill odors. Some people can smell
hydrogen sulfide (individual’s odor threshold) at concentrations as low as 0.5 parts per billion (ppb).
However, the odor threshold can vary significantly among individuals based on the olfactory sensitivity of
the person. For many compounds, including hydrogen sulfide, there is a wide variability in published odor
thresholds (refer to Table 1). Odors alone cannot be relied upon as providing an early warning for
elevated concentrations of hydrogen sulfide. “At concentrations around 100 ppm,” (parts per million)
“no odor is detected due to a loss of olfactory sensation, resulting in loss of warning properties at lethal
levels.” (Integrated Risk Information System (IRIS)). Hydrogen sulfide is more dense than air, and
therefore, more likely to pool at lower elevations under still conditions, depending upon topography.

……..

Above paragraph is an excerpt from  Appendix A – Basics of Landfill Gas (Methane, Carbon Dioxide, Hydrogen Sulfide and Sulfides):  http://www.mass.gov/dep/recycle/laws/lfgasapp.pdf 

The full document is Control of Odorous Gas at Massachusetts Landfills (http://www.mass.gov/dep/recycle/laws/lfgaspol.pdf) published on the website of the

COMMONWEALTH OF MASSACHUSETTS
EXECUTIVE OFFICE OF ENVIRONMENTAL AFFAIRS
DEPARTMENT OF ENVIRONMENTAL PROTECTION

Link to Full Document:  http://www.epa.gov/IRIS/toxreviews/0061tr.pdf

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MAJOR CONCLUSIONS IN THE CHARACTERIZATION OF HAZARD AND DOSE RESPONSE

6.1. HAZARD IDENTIFICATION

Hydrogen sulfide is a colorless gas and has a strong odor of rotten eggs. Its primary uses include the production of elemental sulfur and sulfuric acid, the manufacture of heavy water and other chemicals, in metallurgy, and as an analytical reagent. Although quantitative data are lacking, toxicity studies suggest that H2S gas is absorbed rapidly through the lungs. Oral exposure is not likely to occur. In animals and humans, it distributes to the blood, brain, lung, heart, liver, spleen, and kidney. Oxidation is the primary metabolic pathway for H2S, with thiosulfate and sulfate as metabolites. Metabolism in laboratory animals and in humans appears to be similar. Hydrogen sulfide is excreted in the urine.

Human data pertaining to inhalation exposure (the expected route of ambient exposure) consist of a plethora of case reports and a variety of occupational epidemiological studies. Although these studies have limitations that preclude their use for quantitative risk assessment, they indicate that exposure to H2S (at high concentrations) has profound effects on the respiratory system leading to unconsciousness with attendant neurologic sequelae and, sometimes, death. An increase in cardiovascular-related deaths due, in part, to H2S exposure was reported in one occupational study.

Inhalation studies in adult rodents demonstrate sensitivity of nasal olfactory epithelium to low concentrations of H2S. The RfC is based on these lesions. Limited evidence suggests that exposure of humans to low concentrations may also cause neurologic symptoms although quantitative exposure-response data is lacking. Because of similar access of inhaled H2S to the olfactory tissues of humans, these lesions are likely of relevance to humans and a reasonable choice as a critical effect. Relevance to olfactory lesions seen in rodents to humans is also suggested by Hirsch and Zavala (1999) who reported decreased persistent olfactory function in workers exposed to hydrogen sulfide chronically. Whereas adverse nasal effects are of relevance and concern in adult human exposure scenarios, inhalation studies of perinatal or neonatal exposure in rats demonstrates abnormal cellular development in the brain as well as significant alterations in neurotransmitter levels; the toxicological significance of these findings is uncertain.

Relevant quantitative human oral toxicity data are not available and ingestion is not a likely route of exposure. An RfD based on GI disturbances in pigs consuming feed containing hydrogen sulfide was derived in the previous IRIS entry. A review of the RfD (see Section 4.2.1) indicates that the effects on which that value were based are not reproducible and probably not related to H2S. Therefore the previous RfD will be withdrawn and a new RfD will not be derived based on data base deficiencies.

The indicators of a possible effect noted in the developing brain cells of newborn rats indicate the possibility that the developing human fetus could also be at risk. The exposure levels producing these effects, however, are in the same range or somewhat higher than those producing the critical sentinel clearly adverse effect (nasal tract lesions) in adult animals, thereby ameliorating the concern that young animals (and possibly children) may be especially susceptible to the effects from relatively low-level chronic exposures to hydrogen sulfide. Other observations in the data base do indicate a possible concern regarding the susceptibility of children exposed to high levels of H2S, i.e., > 600 ppb. However, the relevance of this apparent susceptibility at environmental levels of H2S where toxicity is not likely to occur, such as the RfC value derived herein, is not at all clear.

There is no evidence indicating that H2S exposure is associated with carcinogenesis. Under the Draft Revised Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1999), data are inadequate for an assessment of the carcinogenic potential of hydrogen sulfide.

…..

Link to Full Document:  http://www.epa.gov/IRIS/toxreviews/0061tr.pdf

Published in the journal of “Occupational & Environmental Medicine” (http://oem.bmj.com)

Abstract (with author affiliations & other articles citing this article):  http://oem.bmj.com/content/56/4/284.abstract)
Full document:  http://oem.bmj.com/content/56/4/284.full.pdf+html

By Alan R Hirsch, Gilberto Zavala

Abstract 

Objective—To study chronic effects of hydrogen sulphide (H2S) on cranial nerve I (nervi olfactorii), which have been only minimally described.

Methods—Chemosensations (smell and taste) were evaluated in eight men who complained of continuing dysfunction 2–3 years after the start of occupational exposure to H2S. Various bilateral (both nostrils) and unilateral (one nostril at a time) odour threshold tests with standard odorants as well as the Chicago smell test, a three odour detection and identification test and the University of Pennsylvania smell identification test, a series of 40 scratch and sniff odour identification tests were administered.

Results—Six of the eight patients showed deficits of various degrees. Two had normal scores on objective tests, but thought that they continued to have problems. H2S apparently can cause continuing, sometimes unrecognised olfactory deficits.

Conclusion—Further exploration into the extent of such problems among workers exposed to H2S is warranted.

(Occup Environ Med 1999;56:284–287)

Occupational and Environmental Medicine (OEM) is an international peer reviewed journal covering current developments in occupational and environmental health worldwide. Original contributions include: epidemiological studies of health concerns related to exposures in the workplace and the environment; human studies employing biological and genomic techniques to investigate the effects of such exposures; exposure assessment studies; evidence based research on the practice of occupational medicine, and new research methods.

Document obtained from the “Energy and Resources Group” (http://erg.berkeley.edu) of The University of California, Berkeley

By Lana Skrtic

Submitted in partial satisfaction of the requirements for the degree of
Master’s of Science
May 2006
Energy and Resources Group
University of California, Berkeley

Full Document:  PDF File

8. Concluding Remarks

The literature on human health and hydrogen sulfide reveals serious and lasting physiological and neurological effects associated  with acute exposure.  The health effects of chronic exposure to lower levels of H2S, as documented in several studies, also include persistent physiological and neurological disturbances.   Oil and gas facilities can be expected to accidentally and routinely emit hydrogen sulfide in concentrations that span a wide range and are associated with a variety of health effects.  Academic studies, my conversations with health department staff, and available data from monitoring projects help establish that hydrogen sulfide is indeed present near oil and gas facilities.

Because people live near oil and gas sites, emissions of H2S may be routinely compromising human health.  The interviews I conducted with people who live close to oil and gas facilities, as well as some research reported in the Literature  Review section, provide evidence of health impacts from exposure to H2S emitted by oil and gas development.  Although the anecdotal  evidence from my interviews is vulnerable to criticism that other pollutants or individual health factors may be responsible for the symptoms, the reported health effects are consistent with hydrogen sulfide exposure.  The fact that concentrations of H2S to which people are exposed are often not known does not imply that hydrogen sulfide is  not the cause of the observed health effects.  The lack of precise exposure data is,  however, one area that future research should address.

……..

As I show in the Regulations and Recommendations section, at the federal level, the oil and gas industry and the paper and pulp industry have exerted their influence to prevent H2S from being included on the Clean Air Act’s Hazardous Air Pollutants (HAPs) list, and to exempt it from reporting under the EPA’s Toxic Release Inventory (TRI).  At the time of writing, the EPA is reviewing both decisions, which at the very least indicates that some concern exists over the lack of stricter regulation of hydrogen sulfide at the federal level.  The level of regulation of hydrogen sulfide varies widely across the states that have established an ambient standard in the absence of a federal one, but again, the very  existence of ambient standards suggests that hydrogen sulfide is a concern.

Monitoring of ambient H2S is necessary to determine exactly how much is being emitted and to clarify the link between exposure and health effects.  Enough evidence of routine H2S emissions at oil and gas facilities emerges from my conversations with health department personnel, interviews with people living near oil and gas sites, several studies summarized in the Literature Review section, and state monitoring projects to merit more comprehensive monitoring.  The lack of federal standards for ambient H2S levels or for emissions of H2S is one reason for sparse monitoring even at state level, since state health / environmental departments largely depend on federal funding for their projects.  More routine and special project monitoring would facilitate conducting community health studies, by providing accurate exposure data that could be matched with observed health effects.

In light of the information presented here on the health effects associated with exposure to hydrogen sulfide, even though rigorous data on the dose-response relationship is lacking, it is irresponsible and callous to delay making some public policy decisions that would help protect human health.

Research Article published in the Journal of Environmental and Public Health (http://www.hindawi.com/journals/jeph/aip/565690/)

Full PDF file

HUMAN IMPAIRMENT FROM LIVING NEAR CONFINED ANIMAL (HOG) FEEDING OPERATIONS (CAFO’S)

Kaye H. Kilburn, M.D.

Ralph Edgington Professor of Internal Medicine
University of Southern California
Keck School of Medicine (ret.)
President- Neuro-test Inc.

ABSTRACT

Problem  To determine whether neighbors around manure lagoons and massive hog confinement buildings who complained of offensive odors and symptoms had impaired brain and lung function.

Method  We compared near hog manure neighbors of lagoons to people living beyond 3 kilometers in Ohio and to unexposed people controls in a nearby state for neurophysiological, cognitive, recall and memory functions, and pulmonary performance.

Results  The 25 exposed subjects averaged 4.3 neurobehavioral abnormalities, significantly different from 2.5 for local controls and 2.3 for Tennessee controls. Exposed subjects mean forced vital capacity and expiratory volume in 1 sec. were reduced significantly compared to local and regional controls.

Conclusions  Near neighbors of hog enclosures and manure lagoon gases had impaired neurobehavioral functions and pulmonary functions and these effects extended to nearby people thought to be controls. Hydrogen sulfide must be abated because people living near lagoons can not avoid rotten egg gas.

This 88-page document is “Chapter 3″ pulled from the “Agency for Toxic Substance & Disease Registry” (http://www.atsdr.cdc.gov/toxprofiles/index.asp) provided by the government’s “Centers for Disease Control and Prevention” (http://www.cdc.gov).

3. HEALTH EFFECTS

3.1 INTRODUCTION

The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and
other interested individuals and groups with an overall perspective on the toxicology of hydrogen sulfide.
It contains descriptions and evaluations of toxicological studies and epidemiological investigations and
provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.

3.2 Discussion of health effects by route of exposure
3.3 Genotoxicity
3.4 Health effects in wildlife potentially relevant to human health
3.5 Toxicokinetics
3.5 Mechanisms of action
3.6 Toxicities mediated through the neuroendocrine axis
3.7 Children’s susceptibility
3.8 Biomarkers of exposure and effect
3.9 Interactions with other chemicals
3.10 Populations that are unusually susceptible
3.11 Methods for reducing toxic effects
3.12 Adequacy of the database

…..

The full chapter on Health Effects can be read online:  http://www.atsdr.cdc.gov/toxprofiles/tp114-c3.pdf.

The full Toxicological Profile for Hydrogen Sulfide (all chapters) can be referenced at:  http://www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=389&tid=67 

Below is an excerpt of the chapter on Hydrogen Sulfide from “Air Quality Guidelines for Europe, Second Edition” published by the World Health Organization, Regional Office for Europe, Copenhagen.

6.6 Hydrogen sulfide

Exposure evaluation
Typical symptoms and signs of hydrogen sulfide intoxication are most
often caused by relatively high concentrations in occupational exposures.
There are many occupations where there is a potential risk of hydrogen
sulfide intoxication and, according to the US National Institute for Occupational
Safety and Health (1), in the United States alone approximately
125 000 employees are potentially exposed to hydrogen sulfide. Low-level
concentrations can occur more or less continuously in certain industries,
such as in viscose rayon and pulp production, at oil refineries and in geothermal
energy installations.

In geothermal areas there is a risk of exposure to hydrogen sulfide for the
general population (2). The biodegradation of industrial wastes has been
reported to cause ill effects in the general population (2). An accidental
release of hydrogen sulfide into the air surrounding industrial facilities can
cause very severe effects, as at Poza Rica, Mexico, where 320 people were
hospitalized and 22 died (2). The occurrence of low-level concentrations of
hydrogen sulfide around certain industrial installations is a well known fact.

Health risk evaluation
The first noticeable effect of hydrogen sulfide at low concentrations is its
unpleasant odour. Conjunctival irritation is the next subjective symptom
and can cause so-called “gas eye” at hydrogen sulfide concentrations of 70–
140 mg/m3. Table 16 shows the established dose–effect relationships for
hydrogen sulfide.

The hazards caused by high concentrations of hydrogen sulfide are relatively
well known, but information on human exposure to very low concentrations
is scanty. Workers exposed to hydrogen sulfide concentrations
of less than 30 mg/m3 are reported to have rather diffuse neurological and
mental symptoms (4) and to show no statistically significant differences
when compared with a control group. On the other hand, changes in haem
synthesis have been reported at hydrogen sulfide concentrations of less than
7.8 mg/m3 (1.5–3 mg/m3 average) (5). It is not known whether the inhibition
is caused by the low concentrations or by the cumulative effects of
occasional peak concentrations. Most probably, at concentrations below
1.5 mg/m3 (1 ppm), even with exposure for longer periods, there are very
few detectable health hazards in the toxicological sense. The malodorous

property of hydrogen sulfide is a source of annoyance for a large proportion
of the general population at concentrations below 1.5 mg/m3, but from the
existing data it cannot be concluded whether any health effects result. The
need for epidemiological studies on possible effects of long-term, low-level
hydrogen sulfide exposure is obvious. A satisfactory biological exposure
indicator is also needed.

The full text excerpt of the chapter on Hydrogen Sulfide can be read here:  AQG2ndEd_6_6Hydrogensulfide.
The full document can be read online:  http://www.euro.who.int/__data/assets/pdf_file/0005/74732/E71922.pdf.

By Joyce A. Ober

(from page 48)
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Losses during handling and shipping solid bulk sulfur have been significant in the past, although difficult to quantify. When sulfur was poured to block in the early days of the industry, the solid material was broken up and moved with bulldozers, creating a tremendous problem with fine sulfur dust. The fine particles were difficult to contain and could be blown great distances on the wind.  In addition to contaminating the area adjacent to the production locations, contamination was a problem along rail lines and at port facilities. Of even more concern than the dust contamination was the hazardous nature of the sulfur dust. Finely divided sulfur presents explosive and fire hazards, and the SO2 generated by such a fire is toxic (West, 1966).48

Because of these issues, regulations were established to limit shipments of crushed and broken sulfur. Several processes have been developed to minimize the loss and lessen the hazards in handling solid sulfur. Domestically, nearly all sulfur is shipped molten, avoiding any of the dusting problems associated with bulk sulfur. If sulfur is poured to block in the U.S. Gulf Coast area, then it is mechanically broken and passed through a melter before it is shipped from the storage site in molten form. During this processing, dust is kept to a minimum by containing dust inside the outer walls of the sulfur block. Most sulfur produced in California and Washington is shipped overseas. To make this material acceptable for bulk transport, the molten sulfur is processed in forming apparatus that solidifies the sulfur into distinct particles, such as granules, pastilles, prills, and slates, that resist breakage, significantly reducing the fines problems during handling. Additional dust suppression techniques include covered conveyors systems, dust collectors, and enclosed railcar unloading facilities with water sprays. These innovations have reduced losses during handling to a minimum.
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For questions about the scientific content of this report, contact Joyce Ober.

U.S. Department of the Interior, U.S. Geological Survey
URL: http://pubs.usgs.gov/of/2002/of02-298/index.html
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Smith Field/Beaufort Windrose Plot

Wind rose

Elisabeth Gray (Chemist from Vanderbilt University) responds with factual rebuttals to erroneous (“fictional”) statements being circulated:

1. Fiction: For years, PCS Phosphate has been conducting the same operations at RadioIsland as they now propose to accomplish at the MHC state port facility.

2. Fiction: The annual emissions into the air will not be changed by the additional processesof moving and melting bulk formed solid sulfur.

3. Fiction: We already have phosphate dust. Sulfur dust is no different or worse than phosphate dust.

Omissions. The documents submitted by PCS to Air Quality seem to furnish contradictoryinformation about the operations that might be the most critical to our environment, theunloading of solid sulfur, the moving of solid sulfur from place to place and transferring solidsulfur to the melting pots.

Her detailed responses are found in the attached document:  PCS July 21-Elisabeth.

Elisabeth also poses some additional questions about issues that need to be specifically addressed by PCS Phosphates:

1. Why are the oxides of nitrogen not modeled? The primary EPA standard for nitrogen dioxide established in April 2010 is 100 ppb.  According to the PCS data in their environmental statement, over 121 times as many molecules of the oxides of nitrogen will be produced as molecules of sulfur dioxide.

2. How is the solid sulfur to be handled? In a closed or an open system?

3. If the system is closed, how much water/day will be used to achieve a 3% by mass of water to bulk sulfur?

4. How will this water be handled after it is sprayed on the sulfur?

5. If the system is an open one, how will the sulfur dust produced be prevented from entering the surrounding waters?

6. How will PCS dispose of this sulfur dust?

7. Will PCS fund a manned, fire station with well trained personnel in the event that a catastrophe occurs? Local capability does not exist.

8. Can we get an Environmental Impact Statement? How? Why not?

9. Is there a Hurricane Preparedness plan?

Highlights…

“Sulfur dioxide dissolves easily in water to form sulfuric acid. Sulfuric acid is a major component of acid rain. Acid rain can damage forests and crops, change the acidity of soils, and make lakes and streams acidic and unsuitable for fish. Sulfur dioxide also contributes to the decay of building materials and paints, including monuments and statues.”

“People who live near industrial sources of sulfur dioxide may be exposed to it in the air.”

“Short term exposure to high enough levels of SO₂ can be life threatening. Generally, exposures to SO₂ cause a burning sensation in the nose and throat. Also, SO₂ exposure can cause difficulty breathing, including changes in the body’s ability to take a breath or breathe deeply, or take in as much air per breath. Long term exposure to sulfur dioxide can cause changes in lung function and aggravate existing heart disease. Asthmatics may be sensitive to changes in respiratory effects due to SO₂ exposure at even low concentrations.”

Full document…

Abbreviated synopsis of the human toxic potential of the most likely air pollutants as described in the environmental assessment from the planned sulfur melting project in Morehead City, NC – James E. Gibson, Ph.D., Fats Professor of Pharmacology and Toxicology the Brody School of Medicine at ECU

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