284 Occup Environ Med 1999;56:284–287 Occup Environ Med: first published as 10.1136/oem.56.4.284 on 1 April 1999. Downloaded from SHORT REPORT Long term eVects on the olfactory system of exposure to hydrogen sulphide Alan R Hirsch, Gilberto Zavala Abstract was overcome and rendered unconscious for Objective—To study chronic eVects of less than a minute. After regaining conscious- hydrogen sulphide (H2S) on cranial nerve ness, a neurological examination showed re- I (nervi olfactorii), which have been only duced memory, impaired concentration, and minimally described. complete loss of the sense of smell. His electro- Methods—Chemosensations (smell and encephalogram (EEG) was normal at that taste) were evaluated in eight men who time. Ten months after the accident, the patient complained of continuing dysfunction 2–3 continued to complain of tiredness, impaired years after the start of occupational expo- initiative, expressive aphasia, and episodes of trembling. His loss of the sense of smell sure to H2S. Various bilateral (both nos- trils) and unilateral (one nostril at a time) persisted, except that he was able to detect odour threshold tests with standard odor- ammonia. Examination at that time showed ants as well as the Chicago smell test, a impaired visual accommodation and fusion, three odour detection and identification but neuropsychological test results were nor- test and the University of Pennsylvania mal. Two years after the exposure, CT, and smell identification test, a series of 40 EEG were normal, as were neuropsychological scratch and sniV odour identification tests test results, and his sense of smell had returned were administered. to normal. Whether his sense of smell was objectively assessed or his subjective evaluation Results—Six of the eight patients showed deficits of various degrees. Two had reported, however, is not documented. normal scores on objective tests, but Our purpose in the present study was to thought that they continued to have prob- evaluate chronic eVects on olfaction after http://oem.bmj.com/ exposure to H2S. lems. H2S apparently can cause continu- ing, sometimes unrecognised olfactory deficits. Conclusion—Further exploration into the Methods extent of such problems among workers SUBJECTS Eight men who came for medical evaluation of exposed to H2S is warranted. (Occup Environ Med 1999;56:284–287) continuing problems with smell and taste had had accidental exposure to H2S during their Keywords: hydrogen sulphide; smell; taste disorders jobs 2–3 years previously. on September 30, 2021 by guest. Protected copyright. Patients 1–4 Hydrogen sulphide (H2S), a colorless gas easily On 8 January 1993, 900 pounds of H2S were recognised at 0.025 ppm by its distinctive rot- released into the environment over a 2.5 hour ten egg odour, is well known to aVect diVuse period at a construction site at a gas refinery in areas of the human nervous system including St Croix, Virgin Islands. Two years later we Smell and Taste the cortex, subcortex, cranial nerves, and examined four of the workers, who had experi- Treatment and peripheral nervous system.12Its eVects on cra- Research Foundation, enced various local irritating eVects including Chicago, IL, USA nial nerves II, V, and VIII have been extensively lacrimation, eye irritation, nausea, vomiting, A R Hirsch documented, but its chronic eVects on cranial headache, sore throat, and skin irritation. They nerve I (nervi olfactorii) have been minimally had also experienced chemosensory phenom- University of Illinois described.34 ena consistent with H S exposure, the smell of School of Medicine, 2 An acute eVect of H S on the olfactory nerve 6 Chicago, IL, USA 2 rotten eggs, and a strong metallic taste. None G Zavala is temporary paralysis, or olfactory fatigue, of the patients had lost consciousness during which disables the sense of smell, rendering it a the accident. At the time of the accident, Correspondence to: poor warning system for detecting the contin- atmospheric H2S concentrations were not Dr Alan R Hirsch, Smell and ued presence of the gas.35 Acute eVects have Taste Treatment and obtained, but in previous months the patients Research Foundation, Water generally been described as transient. had been exposed to similar low level releases, Tower Place, Suite 990W, Chronic eVects of H2S on the olfactory when the recorded concentrations of H2S were 845 North Michigan Avenue, system have been described in only one as high as 243 ppm in the work area. The past Chicago, IL 60611, USA. instance5: a 46 year old man working next to a exposures of these four patients is considered Accepted 23 October 1998 sludge centrifuge at a sewage treatment plant chronic. Long term eVects on the olfactory system of exposure to hydrogen sulphide 285 Occup Environ Med: first published as 10.1136/oem.56.4.284 on 1 April 1999. Downloaded from Table 1 Clinical data 3 years after exposure to H2S At refinery construction site (chronic) At petroleum plant gas leak (acute) Patient No 1 2345678 Age (y) 45 39 44 41 52 69 40 61 Loss of consciousness with exposure No No No No Yes Yes Yes Yes Rate of exposure Chronic Chronic Chronic Chronic Acute Acute Acute Acute Onset of taste problem 3 Months after 5–10 Months Immediate 2 Years after Unknown 1–1.5 Years Unknown Immediate after after Onset of smell problem 1 Month after 5–10 Months Immediate Unknown Immediate 1–1.5 Years Immediate Immediate after increase after Rate of deficit Increased then Increased then Increased then Increased then No change No change No change No change no change no change no change no change Duration of deficit To present To present To present To present To present To present To present To present Phantosmia? No Yes No No No No No No Encephalopathy? Subclinical Clinical Clinical Clinical Clinical Clinical Clinical Clinical Smell tests: Amoore’s bilateral (25 ds): IV acid Abnormal Abnormal Normal Normal Abnormal Normal Normal Diacetyl Abnormal Abnormal Normal Abnormal Normal Normal Normal l-Carvone Normal Normal Normal Normal Normal Normal Normal PE-alcohol Normal Abnormal Normal Normal Normal Normal Normal Thiophane Normal Normal Normal Normal Abnormal Normal Abnormal Chicago smell test (CST) 4 of 6 4 of 6 4 of 6 4 of 6 6 of 6 3 of 6 3 of 6 4 of 6 UPSIT smell ID 30 of 40 35 of 40 35 of 40 38 of 40 29 of 40 17 of 40 23 of 40 Mild hyposmia Normosmia Normosmia Normosmia Moderate Anosmia Severe hyposmia hyposmia Amoore’s unilateral thresholds: PM carbinol Normal Normal Normal Normal Abnormal Abnormal PE phenol Normal Normal Normal Normal Normal Normal Naphthalene Normal Normal Normal Normal Normal Normal Pyridine Normal Normal Normal Normal Normal Normal Cineole Normal Normal Normal Normal Abnormal Normal ISOB-ISOB Normal Normal Normal Normal Normal Normal IA acetate Normal Abnormal Normal Normal Normal Normal PD lactone Normal Abnormal Normal Normal Abnormal Normal CA phenone Normal Normal Normal Normal Normal Normal Thiophane (ds) 15/15 Normal 15/25 Normal 15/15 Normal 20/15 Normal 40/20 35/25 Hyposmia Hyposmia Patients 5–8 in preparation for objective tests. They then On 14 May 1993, four workers were sent as underwent bilateral (with both nostrils simulta- part of a crew to fix a gas leak at a petroleum neously) odour detection tests according to the plant in Texas. On their arrival at the site of the methods of Amoore and Ollman7 with the fol- leak, the workers noted fumes coming out from lowing standard odorants at concentrations of underground. They also noted that in the sur- 25 decismels (ds), a normally detectable level rounding area, the odour of rotten eggs was (the ds scale of odour levels is modelled after strong, the grass was brown, and birds lay dead. the decibel scale of sound levels): phenyl ethyl http://oem.bmj.com/ The workers descended into a trenching methylethyl carbinol (pm carbinol), isovaleric system 8 feet deep, 7 feet wide, and 12 feet acid (iv-acid), 2,3 butanedione (diacetyl), pen- long. None wore protective garb. While at- tadecalactone (pd-lactone), 1-carvone, phe- tempting to fix the broken pipe, all were nylethyl alcohol (pe-alcohol), and tetrahydro- overcome by the gas and were unconscious for thiophene (thiophane). They also underwent several minutes before being discovered. They the Chicago smell test, consisting of three were treated for gas intoxication, were admitted forced choice questions pertaining to odour to the intensive care unit, and spent at least a and three open ended questions pertaining to on September 30, 2021 by guest. Protected copyright. week in hospital. At the time of exposure, odour identification.89 Most also underwent atmospheric H2S concentrations were not other olfactory tests: the University of Pennsyl- obtained, but 3 days after the accident, the vania smell identification test (UPSIT), a series concentration of H2S in the gas leaking out of of 40 scratch and sniV forced choice odour the pipe into the trench was 2873 ppm as identification questions scored according to measured by the United States Department of age and sex as described in the published Labor and the Occupational Safety and Health guidelines for the UPSIT10 11; and the unilateral Administration (OSHA). When we examined (one nostril at a time) threshold tests of the four patients, 2.5 years had elapsed since Amoore and Ollman for pm carbinol, para their acute exposure. There were no known ethyl phenol (pe-phenol), naphthalene, pyrid- past or subsequent exposures to H2S in these ine, 1,8 cineole (cineole), isobutyl isobutyrate subjects. (isob-isob), isoamyl acetate (ia-acetate), pd- lactone, á-chloroacetophenone (ca-phenone), Clinical evaluation and thiophane. (Unilateral threshold tests are All patients were asked their subjective experi- scored as normal when either the right or left ence of anosmia, hyposmia (decreased odour nostril is normal, as described by Amoore and sensitivity), hyperosmia (increased odour sen- Ollman.)7 sitivity), phantosmia (phantom smells), dysos- mia (deranged sense of smell), hypogeusia (decreased taste sensitivity), phantogeusia (the Results taste equivalent of phantosmia), and dysgeusia At the time of our evaluations, all patients had (the taste equivalent of dysosmia).