Hydrogen Sulphide
General Information
Key Points
Fire




Very flammable
Reacts with metals, metal oxides and strong oxidising agents. Heating may cause
violent combustion
Emits toxic fumes of sulphur oxides when heated to decomposition
In the event of a fire involving hydrogen sulphide, use fine water spray and gas tight
kit with breathing apparatus
Health






Toxic by inhalation
Very toxic
Inhalation of high concentrations may lead to collapse, inability to breathe and death
within minutes.
Following single or repeated exposure to high concentrations a range of effects on
the nervous and cardiovascular system may occur.
Skin exposure causes skin discolouration, pain, itching, skin redness and local
frostbite if exposed to liquefied hydrogen sulphide gas
Eye effects may be delayed and include irritation, inflammation, tearing, sensitivity to
light and conjunctivitis
Environment


Dangerous for the environment
Inform Environment Agency of substantial incidents
Prepared by the Toxicology Department
CRCE, PHE
2009
Version 1
HYDROGEN SULPHIDE – GENERAL INFORMATION
Background
Hydrogen sulphide is a colourless,
flammable gas with a characteristic odour
of rotten eggs. It is produced both
naturally and through human activity.
Hydrogen sulphide is one of the key
compounds in the natural cycle of sulphur
in the environment. It is produced during
the decay of plant and animal protein and
it occurs in volcanic gases. Some natural
gas fields and geothermally active areas
have found significant concentrations of
hydrogen sulphide.
Skin exposure may also occur, which may
cause discolouration, pain, itching,
redness of skin and local frostbite. Eye
exposure
may
cause
irritation,
inflammation, tearing, sensitivity to light
and conjunctivitis.
Hydrogen sulphide is usually produced as
an undesirable by-product, such as in the
production of coke from sulphur-containing
coal, the refining of sulphur-containing
crude oils and from producing wood pulp.
However in some processes it is an
important reagent or intermediate such as
in the manufacture of sulphuric acid,
inorganic sulphides and as an agricultural
disinfectant.
Exposure to hydrogen sulphide usually
occurs as a result of an accidental spill or
leak during transportation, manufacturing
or disposal. Occupational exposure may
occur in oil, gas and petrochemical
industries.
Hydrogen sulphide is a gas therefore it is
most likely to be breathed in. Skin and eye
contact may also occur. The nervous
system and cardiovascular system are
most affected by hydrogen sulphide,
leading to a range of symptoms. Single
exposures to high concentrations may
rapidly cause breathing difficulties and
death.
General Information: Page 2 of 3
HYDROGEN SULPHIDE – GENERAL INFORMATION
Frequently Asked Questions
What is hydrogen sulphide?
Hydrogen sulphide is a colourless, flammable gas with a characteristic odour of rotten eggs.
How does hydrogen sulphide get into the environment?
Hydrogen sulphide occurs both naturally and through human activity. It may be released
from a number of human activities such as production of coke from sulphur-containing coal,
the refining of sulphur-containing crude oils and from producing wood pulp.
How will I be exposed to hydrogen sulphide?
You may be exposed to hydrogen sulphide by breathing it in, or skin and eye contact.
If there is hydrogen sulphide in the environment will I have any adverse health
effects?
The presence of hydrogen sulphide in the environment does not always lead to exposure.
Clearly, in order for it to cause any adverse health effects you must come into contact with it.
You may be exposed by breathing it in, or by skin and eye contact. Following exposure to
any chemical, the adverse health effects you may encounter depend on several factors,
including the amount to which you are exposed (dose), the way in which you are exposed,
the duration of exposure, the form of the chemical and if you were exposed to any other
chemicals.
Health effects following inhalation of high concentrations of hydrogen sulphide may include
collapse, inability to breathe and death within minutes. A range of effects on the nervous and
cardiovascular system may occur following single or repeated exposures to high hydrogen
sulphide concentrations. Skin discolouration, pain, itching, skin redness and local frostbite
may occur if skin is exposed to compressed hydrogen sulphide liquid. Eye exposure may
cause irritation, inflammation, tearing, sensitivity to light and conjunctivitis.
Can hydrogen sulphide cause cancer?
There is no evidence to suggest that exposure to hydrogen sulphide would cause cancer in
humans.
Does hydrogen sulphide affect children or damage the unborn child?
Children will be affected by hydrogen sulphide in the same way as adults, however because
hydrogen sulphide is heavier than air and children are shorter than adults, children may be
exposed to higher concentrations than adults. There is no evidence to suggest that exposure
to hydrogen sulphide can affect the health of the unborn child.
What should I do if I am exposed to hydrogen sulphide?
It is very unlikely that the general population will be exposed to a level of hydrogen sulphide
high enough to cause adverse health effects.
This document has been created by the PHE Centre for Radiation, Chemical and Environmental
Hazards. The information contained in this document is correct at the time of its publication.
General Information: Page 3 of 3
Hydrogen Sulphide
Incident Management
Key Points
Fire



Very flammable
Incompatible with metals and strong oxidising agentsEmits toxic fumes of sulphur
oxides when heated to decomposition
In the event of a fire involving hydrogen sulphide, use fine water spray and gas tight
kit with breathing apparatus
Health




Toxic by inhalation
Prolonged inhalation causes respiratory tract irritation and systemic effects including
vomiting, diarrhoea, headache,s dizziness, drowsiness, tachycardia and
convulsionsInhalation of high concentrations leads rapidly to collapse, respiratory
paralysis, coma cardiac arrhythmias and death
Eye exposure causes pain, blepharospasm, lacrimation, conjunctivitis and
photophobia
Dermal contact can result in itching, pain, redness and skin discolouration
Environment



Acute hazard to the aquatic environment
Inform Environment Agency of substantial incidents
Prepared by the Toxicology Department
CRCE, PHE
02/2013
Version 2
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Hazard Identification
Standard (UK) Dangerous Goods Emergency Action Codes(a)
UN
1053
EAC
2WE
APP
A(cf)
Hydrogen sulphide
Use fine water spray.
Wear liquid-tight chemical protective clothing in combination
with breathing apparatus*.
Danger that the substance can be violently or explosively
reactive.
Spillages and decontamination run-off should be prevented
from entering drains and watercourses.
There may be a public safety hazard outside the immediate
area of the incident**.
Gas-tight chemical protective suit with breathing apparatus.
Liquefied flammable gas with a boiling point below -20 oC.
Class
2.3
Toxic gases
Sub
risks
2.1
Flammable gases
263
Toxic gas, flammable
Hazards
HIN
UN – United Nations number; EAC – Emergency Action Code; APP – Additional Personal
Protection; HIN - Hazard Identification Number
*Liquid-tight chemical protective clothing (BS 8428) in combination with self-contained open
circuit positive pressure compressed air breathing apparatus (BS EN 137).
** People should stay indoors with windows and doors closed, ignition sources should be
eliminated and ventilation stopped. Non-essential personnel should move at least 250 m
away from the incident.
a
Dangerous Goods Emergency Action Code List 2011. National Chemical Emergency Centre
(NCEC). The Stationary Office, London.
Incident Management: Page 2 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Chemical Hazard Information and Packaging for Supply Classification(a)
Classification
Risk phrases
Safety phrases
F+
Very flammable
T+
Very toxic
N
Dangerous for the environment
R12
Extremely flammable
R26
Very toxic by inhalation
R50
Very toxic to aquatic organisms
S1/2
Keep locked up and out of the reach of children
S9
Keep container in a well-ventilated place
S16
Keep away from sources of ignition - No smoking
S36
Wear suitable protective clothing
S38
S45
S61
In case of insufficient ventilation wear suitable respiratory
equipment
In case of accident or if you feel unwell seek medical advice
immediately (show the label where possible)
Avoid release to the environment. Refer to special
instructions/safety data sheet
a
Annex VI to Regulation (EC) No 1272/2008 on Classification, Labelling and Packaging of
Substances and Mixtures- Table 3.2.
http://esis.jrc.ec.europa.eu/index.php?PGM=cla (accessed 02/2013)
Incident Management: Page 3 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Globally Harmonised System of Classification and Labelling of Chemicals
*
(GHS)(a)
Flam. Gas 1
Flammable gas, category 1
Press. Gas
Gas under pressure
Hazard
Class and
Category
Hazard
Statement
Acute Tox. 2
Acute toxicity (inhalation), category 2
Aquatic Acute
1
Acute hazard to the aquatic environment
H220
Extremely flammable gas.
H330
Fatal if inhaled.
H400
Very toxic to aquatic life.
Signal
DANGER
Words
* Implemented in the EU on 20 January 2009.
a
Annex VI to Regulation (EC) No 1272/2008 on Classification, Labelling and Packaging of
Substances and Mixtures- Table 3.1.
http://esis.jrc.ec.europa.eu/index.php?PGM=cla (accessed 02/2013)
Incident Management: Page 4 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Physicochemical Properties
CAS number
7783-06-4
Molecular weight
34.0
Empirical formula
H2S
Common synonyms
H2S, hydrosulphuric acid, sulphur hydride, dihydrogen
monosulphide
State at room temperature
Gas
Volatility
Vapour pressure = 20 atm (at 25.5 oC)
Specific gravity
1.19 (air = 1)
Flammability
Highly flammable
Lower explosive limit
4.3 %
Upper explosive limit
46 %
Reaction or degradation
products
0.5 g 100 ml-1 water at 20 oC.
Soluble in water. Water solutions of hydrogen sulphide are not
stable; absorbed oxygen leads to the formation of elemental
sulphur and such solutions rapidly become turbid. Soluble in
glycerol, alcohol, gasoline, crude oil, and kerosene
May form explosive mixture with air. It may easily be ignited by
sparks, flames or heat. Note wide explosive limits. Incompatible
with metals and strong oxidizing agents.. Heating may cause
violent combustion or explosion. Attacks many metals and some
plastics.
The substance decomposes on burning producing toxic gases
(sulphur oxides).
Odour
Strong odour of rotten eggs
Water solubility
Reactivity
S
Structure
H
H
(a,b,c)
Table references
a
Hydrogen sulphide (HAZARDTEXT® Hazard Management). In: Klasco RK (Ed): TOMES® System,
Thomson Micromedex, Greenwood Village, Colorado, USA. (electronic version). RightAnswer.com,
Inc., Midland, MI, USA, Available at: http://www.rightanswerknowledge.com (accessed 02/2013).
b
International Programme on Chemical Safety (IPCS): Hydrogen sulphide. International Chemical
Safety Card: 0165,.2000, WHO: Geneva.
c
The Merck Index (14th Edition). Entry 4800:Hydrogen sulphide, 2006.
Incident Management: Page 5 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Threshold Toxicity Values
EXPOSURE VIA INHALATION
ppm
mg m-3
10 - 20
15 - 30
50 - 100
SIGNS AND SYMPTOMS
REFERENCES
Threshold for eye irritation
a
70 – 140
Serious eye damage
a
150 - 250
210 - 350
Loss of olfactory sense
a
320 - 530
450 - 750
530 - 1000
750 - 1400
1000 - 2000
1400 - 2800
Pulmonary oedema with risk of
death
Strong CNS stimulation,
hyperpnoea followed by respiratory
arrest
Immediate collapse with paralysis
of respiration
a
a
a
a
Air Quality Guidelines for Europe. World Health Organization Regional Office for Europe,
Copenhagen WHO Regional Publications, European Series, No. 91, Second Edition, 2000.
Incident Management: Page 6 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Published Emergency Response Guidelines
Emergency Response Planning Guideline (ERPG) Values(a)
ERPG-1*
ERPG-2**
ERPG-3***
Listed value
(ppm)
0.1
30
100
Calculated value
(mg m-3)
0.14
41.72
139.06
* Maximum airborne concentration below which it is believed that nearly all individuals could be
exposed for up to 1 hr without experiencing other than mild transient adverse health effects or
perceiving a clearly defined, objectionable odour.
** Maximum airborne concentration below which it is believed that nearly all individuals could be
exposed for up to 1 hr without experiencing or developing irreversible or other serious health effects
or symptoms which could impair an individual's ability to take protective action.
*** Maximum airborne concentration below which it is believed that nearly all individuals could be
exposed for up to 1 hr without experiencing or developing life-threatening health effects.
Acute Exposure Guideline Levels (AEGLs) (b)
AEGL-1†
AEGL-2††
AEGL-3†††
10 min
0.75
41
76
30 min
0.60
32
59
ppm
60 min
0.51
27
50
4 hr
0.36
20
37
8 hr
0.33
17
31
†
The level of the chemical in air at or above which the general population could experience notable
discomfort.
††
The level of the chemical in air at or above which there may be irreversible or other serious longlasting effects or impaired ability to escape.
†††
The level of the chemical in air at or above which the general population could experience lifethreatening health effects or death.
a
American Industrial Hygiene Association (AIHA). 2011 Emergency Response Planning Guideline
Values.
http://www.aiha.org/insideaiha/GuidelineDevelopment/ERPG/Documents/2011erpgweelhandbook_tab
le-only.pdf (accessed 01/2013).
b
U.S. Environmental Protection Agency. Acute Exposure Guideline Levels,
http://www.epa.gov/oppt/aegl/pubs/chemlist.htm (accessed 01/2013).
Incident Management: Page 7 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Exposure Standards, Guidelines or Regulations
Occupational Standards
LTEL(8 hour reference period): 5 ppm (7 mg m-3)
WEL(a)
STEL(15 min reference period):10 ppm (14 mg m-3)
Public Health Guidelines
DRINKING
WATER QUALITY GUIDELINE(b)
It is unlikely that a person could consume a harmful
dose of hydrogen sulphide from drinking-water;
hence, a health-based guideline value has not
been derived for this compound.
Taste and odour threshold estimated to be
between: 0.05 and 0.1 mg L-1
AIR QUALITY GUIDELINE
(c)
SOIL GUIDELINE VALUE AND
HEALTH CRITERIA VALUES
0.15 mg m-3 with an averaging time of 24 hours.
Concentrations should not be allowed to exceed
7 μg m-3 with a 30-minute averaging period
Data not available
WEL – Workplace exposure limit; LTEL - Long-term exposure limit; STEL – Short-term
exposure limit
a
EH40/2005 Workplace Exposure Limits (second edition, published 2011).
http://www.hse.gov.uk/pubns/priced/eh40.pdf (accessed 01/2013)
b
Guidelines for Drinking-Water Quality, Fourth Edition. WHO, Geneva. 2011.
c
Air Quality Guidelines for Europe. World Health Organization Regional Office for Europe,
Copenhagen WHO Regional Publications, European Series, No. 91, Second Edition, 2000.
Incident Management: Page 8 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Health Effects
Major Route of Exposure(a)

Toxic by inhalation
Immediate Signs or Symptoms of Acute Exposure(a)




Prolonged inhalation exposure causes respiratory tract irritation, with rhinitis,
pharyngitis, bronchitis, dyspnoea and pulmonary oedema. Systemic effects include
vomiting, diarrhoea, headache, nystagmus, dizziness, agitation, drowsiness, tremor,
muscular weakness, convulsions, tachycardia and hypotension.
Inhalation of high concentrations leads rapidly to collapse, respiratory paralysis,
cyanosis, convulsions, coma, cardiac arrhythmias and death within minutes.
Eye exposure causes pain, blepharospasm, lacrimation, conjunctivitis, palpebral
oedema and photophobia.
Dermal contact can result in pain, itching, redness and skin discolouration may occur.
Exposure to the compressed liquid may cause frostbite injury.
TOXBASE - http://www.toxbase.org (accessed 02/2013)
a
TOXBASE: Hydrogen sulphide, 2012.
Incident Management: Page 9 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
Decontamination and First Aid
Important Notes


Ambulance staff, paramedics and emergency department staff treating chemicallycontaminated casualties should be equipped with Department of Health approved,
gas-tight (Respirex) decontamination suits based on EN466:1995, EN12941:1998
and prEN943-1:2001, where appropriate.
Decontamination should be performed using local protocols in designated areas such
as a decontamination cubicle with adequate ventilation.
Dermal Exposure(a)




Decontamination not necessary as it is gas.
Removing patient's clothing and washing the skin with water and a mild detergent
may reduce the risk of odour related complaints in healthcare personnel, but this is
not a priority if dealing with a critically ill patient.
If the skin has been exposed to compressed liquid treat frostbite injury
conventionally.
Other measures as indicated by the patient's clinical condition.
Ocular Exposure(a)




Remove patient from exposure.
Remove contact lenses if present and immediately irrigate the affected eye
thoroughly with water or 0.9% saline for at least 10 – 15 minutes. Continue until the
conjunctival sca pH is normal (7.5 – 8.0). Retest after 20 minutes and use further
irrigation if necessary.
Any particles lodged in the conjunctival recesses should be removed.
Patients with corneal damage and those whose symptoms do not resolve rapidly
should be referred for urgent ophthalmological assessment.
Inhalation(a)






Maintain a clear airway and ensure adequate ventilation.
Remove from exposure and give oxygen in as high a concentration as possible, if
necessary via an endotracheal tube.
Monitor pulse, blood pressure, oxygen saturation and cardiac rhythm.
Perform a 12 lead ECG.
If the patient has clinical features of bronchospasm treat conventionally with
nebulised bronchodilators and steroids.
Apply other supportive measures as indicated by the patient’s clinical condition
Ingestion

Not applicable
TOXBASE - http://www.toxbase.org (accessed 02/2013)
a
TOXBASE: Hydrogen sulphide, 2012.
Incident Management: Page 10 of 11
HYDROGEN SULPHIDE – INCIDENT MANAGEMENT
This document from the PHE Centre for Radiation, Chemical and Environmental Hazards reflects
understanding and evaluation of the current scientific evidence as presented and referenced in this
document.
Incident Management: Page 11 of 11
Hydrogen Sulphide
Toxicological Overview
Key Points
Kinetics and metabolism




Hydrogen sulphide is a gas that is rapidly absorbed by the lungs into the
bloodstream.
It is widely distributed throughout the body.
Metabolism of hydrogen sulphide occurs by oxidation, methylation or reaction with
metalloproteins and the principal product is sulphate.
Hydrogen sulphide is excreted rapidly from the body in the form of sulphate in urine.
Health effects of acute exposure





The major route of exposure is by inhalation.
Acute inhalation exposure to high concentrations may result in effects on the
respiratory, neurological, ocular and cardiovascular systems.
Exposure to low concentrations may result in irritation to the mucous membranes of
the eyes and respiratory tract.
Following acute ocular exposure, eye irritation, with keratoconjunctivitis, punctate
corneal erosion, blepharospasm, lacrimation and photophobia may occur.
Dermal exposure may result in discolouration, pain, itching, erythema (redness of
skin) and local frostbite.
Health effects of chronic exposure


Limited data suggest that effects from repeated exposure are similar to those for
acute exposure, with respiratory, neurological and ocular effects at high
concentrations.
There are no adequate data on chronic toxicity/carcinogenicity.
Prepared by the Toxicology Department
CRCE, PHE
2011
Version 2
HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
Toxicological Overview
Summary of Health Effects
Hydrogen sulphide is a gas and, therefore, inhalation is the most relevant route of exposure
to humans [1].
Acute inhalation exposure to low concentrations of hydrogen sulphide may result in irritation
to the mucous membranes of the eye and respiratory tract. Acute exposure to high
concentrations of hydrogen sulphide results in depression of the nervous system, loss of
consciousness and respiratory paralysis. Other health effects have been reported, the most
sensitive being the respiratory, neurological and ocular system [1, 2].
Data on the effects in humans following repeated exposure are limited and difficult to
interpret because of co-exposure to other chemicals. There is some limited evidence to
suggest an association with spontaneous abortions, but the effects seen were small and
confounded by exposure to other chemicals, therefore no conclusions could be drawn.
Studies in experimental animals exposed to high concentrations of hydrogen sulphide via
inhalation have resulted in respiratory and cardiovascular effects. The most sensitive target
organ in animals following acute inhalation exposure was the respiratory tract [2]. No chronic
studies have been reported in experimental animals exposed to hydrogen sulphide.
Hydrogen sulphide is not considered to be mutagenic or a reproductive or developmental
toxicant.
There are inadequate data on the carcinogenicity of hydrogen sulphide in humans or
experimental animals. Hydrogen sulphide is not listed as a carcinogen by the International
Agency for Research on Cancer (IARC) [3].
Toxicological Overview: Page 2 of 10
HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
Kinetics and Metabolism
The primary route of hydrogen sulphide exposure is via inhalation and to a lesser extent via
dermal and ocular absorption [1, 2]. It is unlikely that oral exposure occurs since hydrogen
sulphide is a gas.
Hydrogen sulphide is absorbed rapidly through the lungs into the bloodstream and
distributed widely throughout the body [1, 2]. Absorption of hydrogen sulphide occurs to a
lesser extent through the gastrointestinal tract and intact skin.
Metabolism of hydrogen sulphide occurs via three pathways: oxidation, methylation and
reaction with metalloproteins or disulphide-containing proteins, the latter being the principal
mechanism [1]. The mechanism of action of hydrogen sulphide is thought to be direct
inhibition of cellular enzymes, such as cytochrome c oxidase, which is involved in cellular
oxidative processes and energy production. Such enzyme inhibition leads to disruption of the
electron transport chain and impairs oxidative metabolism, leading to anaerobic metabolism,
decreased ATP production and generation of lactic acid [1, 2].
The major detoxication pathway for hydrogen sulphide in humans is via oxidation in the liver
[1]. Hydrogen sulphide is rapidly eliminated from the body in the form of sulphate in urine,
with peak levels around 15 hours after exposure [2]. It may also be excreted unchanged in
exhaled air and, in faeces and flatus.
Sources and Route of Human Exposure
Hydrogen sulphide is produced both naturally and through human activity.
Most endogenous production results from the metabolism of sulphydryl-containing amino
acids, e.g. cysteine, by bacterium in the intestinal tract and mouth. It is also produced in the
brain and smooth muscle [1].
Exposure to hydrogen sulphide may occur via inhalation, dermal or ocular routes [1].
Hydrogen sulphide is a gas and therefore, inhalation exposure is the most relevant route to
humans [2].
In the UK and EU, long-term exposure limits (LTEL) for hydrogen sulphide is 7 mg/m3 (8hour time weighted average (TWA) exposure reference period) [4, 5]. The short-term
exposure limit in the UK (STEL) is 14 mg/m3 (15-minute reference period) [4].
The World Health Organization (WHO) has not set a health-based guideline value in drinking
water. The presence of hydrogen sulphide in drinking water is easily detected by odour or
taste and hence, although oral toxicity data are lacking, it is unlikely that a person could
consume a harmful dose of hydrogen sulphide from drinking water [6] .
Toxicological Overview: Page 3 of 10
HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
Health Effects of Acute / Single Exposure
Human Data
Inhalation
Exposure to concentrations of about 700 mg/m3 (500 ppm) hydrogen sulphide and above
may be fatal. Respiratory failure was the most common cause of death, but a wide range of
health effects have been reported following exposure to high concentrations including
respiratory, neurological and cardiovascular effects [1, 2].
Neurological effects at high exposure have included nausea, headache, delirium, disturbed
equilibrium, poor memory, neurobehavioral changes, olfactory paralysis, loss of
consciousness, tremors and convulsions. In those surviving exposure to high concentrations
some of the neurological effects may be permanent or persistent. Cardiac irregularities
including arrhythmias as well as hypertension have been reported [1, 2].
No adverse cardiovascular effects were seen in healthy volunteers exposed to 7 or 14
mg/m3 (5 and 10 ppm) for 30 minutes of submaximal exercise, nor were any changes seen
in pulmonary function tests in separate studies when healthy volunteers were exposed to 14
mg/m3 (10 ppm) for 15 minutes. However, asthmatics were more sensitive, with
bronchoconstriction and headache being observed after exposure to 2.8 mg/m3 (2 ppm).
hydrogen sulphide concentration. This was considered the Lowest Observed Adverse Effect
Level (LOAEL) [1].
Although the odour threshold has been reported to be around 0.011 mg/m3 (0.008 ppm) in
naïve subjects, olfactory paralysis occurs at greater than about 140 mg/m3 (100 ppm). The
loss of odour perception makes hydrogen sulphide especially dangerous since a few breaths
at around 700 mg/m3 (500 ppm) is lethal [1].
Table 1 outlines the health effects associated with various concentrations of hydrogen
sulphide.
Table 1 – Human health effects of hydrogen sulphide at various concentrations [1].
mg/m3
0.011
2.8
5.0
7 or 14
ppm
0.008
2
4
5 or 10
5-29
28
>140
>560
≥700
4-21
20
>100
>402
≥502
Exposure via Inhalation
Signs and symptoms
Odour threshold
Bronchial constriction in asthmatic individuals
Increased eye complaints
Increased blood lactate concentration, decreased skeletal muscle citrate
synthase activity, decreased oxygen uptake
Eye irritation
Fatigue, loss of appetite, headache, irritability, poor memory, dizziness
Olfactory paralysis
Respiratory distress
Death
Ingestion
No data could be located regarding the human health effects following acute oral exposure
to hydrogen sulphide, but exposure by this route is unlikely.
Toxicological Overview: Page 4 of 10
HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
Dermal / ocular exposure
Acute exposure of six men to hydrogen sulphide resulted in facial peeling in one man
exposed to probable concentrations of 11-22 mg/m3 (8-16 ppm) [1, 2]. Exposure to hydrogen
sulphide gas does not induce any appreciable absorption through intact skin in humans [7].
Hydrogen sulphide gas is an eye irritant, with keratoconjunctivitis, punctate corneal erosion,
blepharospasm, lacrimation, and photophobia having developed in individuals exposed
briefly to high concentrations (concentration not specified) [1, 2]. There have been reports of
severe damage to eye tissues following exposure to hydrogen sulphide concentrations of
>70 mg/m3 (50 ppm) for 1 hour or more [1]. In a separate study, workers exposed to
hydrogen sulphide at concentrations of 15-29 mg/m3 (11-21 ppm) for 6-7 hours reported eye
irritation. A LOAEL of 15 mg/m3 could be identified from these observations.
Delayed effects following an acute exposure
In individuals surviving exposure to high levels of hydrogen sulphide the neurological effects
may be permanent or persistent.
Animal and In-Vitro Data
Inhalation
The mortality rate induced by hydrogen sulphide in experimental animals is dependent on
the species, strain and concentration to which they are exposed. Table 2 outlines the effect
hydrogen sulphide has on mortality in experimental animals.
Table 2 – Effects on mortality following exposure to hydrogen sulphide in
experimental animals [1, 2]
Species
Strain
Sex
Number
Mouse
CB20
Male
30
Hydrogen
sulphide
concentration
mg/m3 (ppm)
139 (100)
Mouse
NMR1
Female
20
139 (100)
Mouse
Not
specified
Not
specified
Not
specified
Male
6
1006 (722)
6
2609 (1872)
10 minutes
5
2307 (1655)
3 minutes
Rat
Not
specified
Not
specified
SpragueDawley
F-344
2 hours/day
(1-4 days)
50 minutes
F-344
Male
697-976 (500700)
≤558 (≤400)
4 hours
Rat
Rat
Wistar
albino
Japanese
white
Male
Not
specified
Not
specified
10
1115 (800)
12 minutes
697-1394
(500-1000)
30 minutes
Mouse
Rat
Rabbit
Not
specified
5
Exposure
time
Effect
2 hours
No
mortality
No
mortality
Mortality
(100%)
Mortality
(100%)
Mortality
(100%)
Mortality
(100%)
No
mortality
Mortality
(100%)
Mortality
(100%)
4 hours
Several studies have been carried out in F344 rats and various parameters reported.
Following exposure to 0, 70, 279 and 558 mg/m3 (0, 50, 200 or 400 ppm) hydrogen sulphide
for 4 hours, cytochrome c oxidase activity in lung mitochondria was significantly decreased
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HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
at all concentrations, with activity only returning to normal levels within 24 hours in animals
exposed to <279 mg/m3 (200 ppm) hydrogen sulphide. The viability of pulmonary alveolar
macrophages decreased in the lung lavage fluid of rats exposed to the highest concentration
and a complete abolition of Zymosan-induced stimulation of respiratory rates of pulmonary
alveolar macrophages was observed in rats exposed to the two highest concentrations. A
NOAEL of 70 mg/m3 could be identified from this study.
In the same study, cellularity of nasal lavage fluid increased at all concentrations and
enzyme activity, indicative of pulmonary epithelium toxicity, increased in rats administered
the highest two doses of hydrogen sulphide. A LOAEL of 14 mg/m3 was derived [2].
Male F344 rats were also exposed to hydrogen sulphide at doses of 0, 116 or 612 mg/m3 (0,
83 and 439 ppm) or 0, 523 or 556 mg/m3 (0, 375 and 399 ppm) for 4 hours. Mild perivascular
oedema was observed in rats exposed to 116 mg/m3 hydrogen sulphide whereas pulmonary
oedema was evident at higher concentrations, as well as effects on bronchiolar epithelium
and alveoli and a decrease in the number of viable pulmonary alveolar macrophage cells [2].
Male Wistar rats were exposed to 0 or 105 mg/m3 (0 and 75 ppm) hydrogen sulphide for 1
hour, resulting in a decrease in heart rate and slight pulmonary congestion. Conversely,
Wistar rats (sex not specified) exposed to 140-279 mg/m3 (100-200 ppm) for 1 hour showed
increased heart and respiratory rates, as well as changes in a number of histological and
biochemical parameters in the respiratory tissues and fluids [1, 2].
Rabbits and rats (sex and strain not specified) exposed to 100 mg/m3 (72 ppm) hydrogen
sulphide for 1.5 hours or 1115 mg/m3 (800 ppm) for 20 minutes were found to lose
consciousness [2].
Ingestion
No data could be located regarding the health effects following acute oral exposure to
hydrogen sulphide in experimental animals.
Dermal / ocular exposure
F344 rats (sex not specified) were exposed to 0, 279 or 558 mg/m3 (0, 200 and 400 ppm)
hydrogen sulphide for 4 hours [2]. Epiphora (watery eye) was observed in rats exposed to
the highest concentration. A NOAEL of 279 mg/m3 was derived from this study.
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HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
Health Effects of Chronic / Repeated Exposure
Human Data
Inhalation
Repeated exposure to hydrogen sulphide by inhalation has resulted in fatigue, poor memory,
dizziness and irritability [1].
Individuals were exposed via inhalation to hydrogen sulphide at <10, 10-30 or >30 µg/m3
(<0.007, 0.007-0.02 and 0.02 ppm) for an unknown period of time at a pulp mill [2]. At the
highest exposure level, a significant increase in nausea was reported. Both nasal (i.e. stuffy
or runny nose) and pharyngeal irritation increased in a dose-dependent manner. However,
the interpretation of these findings should be treated with caution since the presence of
multiple sulphur compounds complicates the results.
Ingestion
No data could be located regarding the human health effects following repeated oral
exposure to hydrogen sulphide, but such exposure is unlikely.
Dermal / ocular exposure
There has been one report of dermal penetration of hydrogen sulphide resulting in toxicosis
in humans exposed to large concentrations (concentration not specified) over a long
exposure period [8]. No further details were available.
A significantly higher prevalence of eye complaints has been reported in workers repeatedly
exposed to hydrogen sulphide levels above 5 mg/m3 (3.7 ppm) compared to unexposed
workers [1].
Genotoxicity
No data could be located regarding genotoxicity in humans following chronic exposure to
hydrogen sulphide.
Carcinogenicity
Hydrogen sulphide is not listed as a carcinogen by the International Agency for Research on
Cancer (IARC) [3].
No data are available to assess the carcinogenicity of hydrogen sulphide in humans.
Reproductive and developmental toxicity
Women living in areas with hydrogen sulphide concentrations exceeding 4 mg/m3 (2.85
ppm) were found to have a non-statistically significant rise in the incidence of spontaneous
abortions [2]. However, these findings were confounded by the presence of other chemicals
also being detected in the same areas.
In a separate study, women who were employed in to work with rayon textile and paper
products showed a statistically significant increase in the rate of spontaneous abortions [1].
This was also observed in those women whose husbands/partners worked in rayon textile or
chemical processing jobs. Furthermore, areas in which annual levels of hydrogen sulphide
was >4 µg/m3 (>0.03 ppm), a rise in the number of spontaneous abortions was observed.
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HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
However, this was not statistically significant. It is important to note here that the chemicals
detected at these places of employment included sulphur dioxide, hydrogen sulphide and
carbon disulphide, the latter compound being a recognised reproductive toxicant.
Animal and In-Vitro Data
Inhalation
One 90 day repeat dose toxicity study in rats and mice was conducted to modern protocol
and conforms to Good Laboratory Practice principles [1]. Male and female F344 rats,
Sprague-Dawley rats or B6C3F1 mice were exposed via inhalation to hydrogen sulphide at
time-weighted average concentrations of 0, 14, 42 or 112 mg/m3 (0, 10, 30 and 80 ppm) for
6 hours/day, 5 days/week for 90 days. No treatment-related changes in histopathological or
haematological parameters were observed nor were any changes in renal function. A
significant decrease in body weight was evident in the Sprague-Dawley rats and B6C3F1
mice exposed to the highest concentration of hydrogen sulphide whereas no changes were
noted in F344 rats. Absolute brain weights were decreased in male Sprague-Dawley rats
exposed to the highest concentration of hydrogen sulphide, but there was no change to
neurological function or neuropathology. Similarly, neurological function and neuropathology
was not altered in F344 rats or B6C3F1 mice. A NOAEL of 42 mg/m3 was identified from this
study based on decreased body weights. The only effect observed at autopsy in the mice
was minimal to mild irritation of the nasal mucosa at the highest dose. No pathological
effects were seen at any dose level in the rat [2].
Male Sprague-Dawley rats exposed to 0 or 70 mg/m3 (0 and 50 ppm) did not exhibit any
neurotoxic effects [2].
Guinea pigs (strain and sex not specified) were exposed daily to 0 or 28 mg/m3 hydrogen
sulphide (0 and 20 ppm) for 1 hour/day for 11 days. Fatigue, somnolence, dizziness and eye
irritation were reported, with decreased cerebral hemisphere and brain stem total lipids and
phospholipids at autopsy [2].
Ingestion
There were limited data available on the ingestion of hydrogen sulphide in animals.
Pigs (strain and sex not specified) were fed hydrogen sulphide at a dose of 0 or 6.7 mg/kg
bw/day for 105 days. Body weight gain was decreased in treated animals compared to
controls [2].
Adult pigs (strain and sex not specified) were fed hydrogen sulphide at a dose of 15 mg/kg
bw/day for a few days. Diarrhoeic digestive disorder was observed. In a repeat study using
younger pigs that weighed less, no diarrheic disorder was noted [2].
Genotoxicity
Hydrogen sulphide gas was not mutagenic in the Ames test employing Salmonella
typhimurium strains TA97, TA98 or TA100, with or without a metabolic activation system [1,
2]. No other data were available.
Carcinogenicity
No data could be located regarding the carcinogenicity of hydrogen sulphide in experimental
animals.
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HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
Reproductive and developmental toxicity
Female Sprague-Dawley rats were exposed to hydrogen sulphide concentrations of 0, 14,
42 or 112 mg/m3 (0, 10, 30 and 80 ppm) for 6 hours/day, 7 days/week for 2 weeks prior to,
and during the 2 week mating period, and on gestational days 0-19. The male animals were
exposed to similar level for 70 days up to and including the mating period. No significant
changes in gestation length, fertility, number of females with live pups, litter size or number
of implants per female were observed. Furthermore, sperm count and morphology were not
altered in the exposed males during this study. No significant alterations in the incidence of
structural anomalies were found in the offspring. Continued exposure of offspring on
postnatal days 5-18 did not show any developmental delays, performance on developmental
neurobehavioral tests or brain histopathology. A reproductive and developmental NOAEL of
42 mg/m3 was identified [2].
Sprague-Dawley rat dams were exposed to hydrogen sulphide concentrations of 0, 28, 70 or
110 mg/m3 (0, 20, 50 and 75 ppm) for 7 hours/day from gestation day 1 through to postnatal
day 21. A significant decrease in time for pinna detachment and hair growth was reported,
but no other changes in development landmarks including incisor eruption, eyelid opening
and surface righting, were noted. The LOAEL for developmental effect was 28 mg/m3 [1, 2].
Pregnant Sprague-Dawley rats were exposed to 0, 140 or 210 mg/m3 hydrogen sulphide (0,
100 and 150 ppm) on gestation days 6-20. Decreased body weight gain was observed at the
highest concentration. No external fetal abnormalities were observed, but a significant,
though slight, decrease in fetal body weight was noted. No developmental effects were
reported [1, 2].
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HYDROGEN SULPHIDE – TOXICOLOGICAL OVERVIEW
References
1.
International Programme on Chemical Safety (IPCS), Hydrogen Sulfide. Concise
International Chemical Assessment Document 53. 2003, WHO: Geneva.
2.
Agency for Toxic Substances and Disease Registry (ATSDR), Toxicological Profile
for Hydrogen Sulfide. 2006, US Department of Health and Human Services: Atlanta,
US.
3.
International Agency for Research on Cancer (IARC), Overall Evaluations of
Carcinogenicity to Humans, in IARC Monographs on the Evaluation of Carcinogenic
Risks to Humans. 2009, IARC: Lyon.
4.
Health and Safety Executive (HSE), EH40/2005 Workplace Exposure Limits. 2005.
5.
Scientific Committee on Occupational Exposure Limits (SCOEL), Hydrogen Sulphide
- Occupational Exposure Limits and Biological Limit Values. 2007, European Union.
6.
World Health Organization (WHO), Guidelines for Drinking-Water Quality: Third
edition. Vol 1. Recommendations. 2006, WHO: Geneva.
7.
International Programme on Chemical Safety (IPCS), Hydrogen sulphide.
Environmental Health Criteria 19. 1981, WHO: Geneva.
8.
Hazardous Substances Data Base (HSDB), Hydrogen sulphide., in Hazardous
Substances Data Base. 1988.
This document from the PHE Centre for Radiation, Chemical and Environmental Hazards reflects
understanding and evaluation of the current scientific evidence as presented and referenced in this
document.
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