Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants Volume 1 (2007) / Chapter Skim
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4 Carbon Monoxide
4 Carbon Monoxide
Pages 67-102
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From page 67... ...
, 24-h, and 90-day exposure guidance levels for CO. The subcommittee's recommendations for CO exposure levels are provided at the conclusion of this chapter along with a discussion of the adequacy of the data for defining those levels and the research needed to fill the remaining data gaps.
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From page 68... ...
68 EEGLs and CEGLs for Selected Submarine Contaminants TABLE 4-1 Physical and Chemical Properties of Carbon Monoxidea Synonyms Carbonic oxide, carbon oxide, flue gas CAS registry number 630-08-0 Molecular formula CO Molecular weight 28.01 ! 191.5°C Boiling point !
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From page 69... ...
. Submariners who smoke theoretically might be subject to additional health risks from environmental exposure given their already elevated COHb levels.
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From page 70... ...
Abbreviations: PB, barometric pressure; PCO2, average partial pressure of carbon dioxide in lung capillaries; VA, alveolar ventilation rate; Vb, blood volume; M, equilibrium constant; DL, diffusing capacity of the lungs; [COHb] o, control value of carboxyhemoglobin prior to carbon monoxide exposure; VCO, rate of endogenous carbon monoxide production.
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. Eleven of 25 patients contacted 2 years after exposure reported seeking medical care for persistent symptoms.
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From page 72... ...
72 TABLE 4-2 Human Toxicity Summary Concentration Exposure Number of (ppm) Duration COHb % Subjects Effects Reference NS NS NS NS Linear relationship described between EPA 1979; Horvath 1981 decline in VO2-max and increasing COHb NS NS 4.5 NS Decrements in brightness discrimination in MacFarland et al.
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NS 5-60 min 15-20 NS Oxygen uptake in tissues unchanged during Chevalier et al. submaximal exercise 1966; Pirnay et al.
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From page 74... ...
maintain 20 reduced oxygen carrying capacity of blood 2000 target COHb by augmenting heart rate, cardiac contractil ity, and cardiac output for submaximal up per and lower body exercise; compensatory mechanisms began to fail at moderate exer cise and CO exposure 11,569 ini- 2.25 h ~17 21 Visual function not affected Hudnell and tially, 142 Benignus 1989 maintenance 500 2 h-2 h and 20 ~26 (after 2 h 6 "Increase in heart rate with minimal exer- Stewart et al.
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From page 75... ...
with a stylus, and the secondary task was announcing or subtracting numbers appear ing on a display 0-1,000; 2 h 30 min ~32 (peak at 2 Headaches noted during exposure became Stewart et al. 1970 gradually ris- 2.5 h)
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From page 76... ...
76 TABLE 4-2 Continued Concentration Exposure Number of (ppm) Duration COHb % Subjects Effects Reference 5, 35, 70 4h 1, 3, 5 30 Dual-task conditions included hand-con- Putz 1979 trolled tracking with low- and high-fre quency conditions and monitoring lights and responding with a button press to indicate brighter lights; differences in tracking per formance noted in the 70-ppm group after 3 h of exposure and in the 35- and 70-ppm exposure groups after 4 h in the high-fre quency condition; reaction times on the light detection task increased in the 35- and 70 ppm exposure groups in the final hour of exposure 70 4h 5 12 Dual-task conditions as in Putz (1979)
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From page 77... ...
0, 50, 100, 4h NS 18 Ability to estimate the length of an auditory Beard and 175, 250 signal, compared with a standard signal, Wertheim 1967 reduced at all CO-exposure concentrations; time to onset of performance deficit de creased with increasing CO exposure <2, 50, 100, 5h Up to 20 27 (in groups No impairment in ability to perform time Stewart et al.
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From page 78... ...
(1983) used dualtask procedures to evaluate neurobehavioral performance at COHb concentrations up to 5.7% for exposure durations of 2.5-4 h.
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Beard and Wertheim (1967) reported decrements in time-estimation ability in a study of 18 subjects exposed to CO at 0, 50, 100, 175, and 250 ppm for 4 h.
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were observed in 3 of the 15 subjects exposed to CO at 15 ppm and in 6 of the 15 subjects exposed to CO at 50 ppm after 2 days of expo
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found increased hematocrit, hemoglobin, and red blood cell counts in smoking and nonsmoking submariners and increased reticulocytes in the smokers. CO concentrations ranged from 15 to 20 ppm, and the average carbon dioxide (CO2)
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The mean daily 1-h maximum CO concentration was 1.8 ppm. There were no significant correlations between CO exposure concentrations and cardiovascular or respiratory admissions.
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. In monkeys exposed to CO at 1,000 ppm for several hours, severe intoxication was observed at 25 min of exposure and was followed by observed deficits in behavioral task performance, physical activity, and coordinated movements (Purser and Berrill 1983)
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From page 84... ...
with myocardial highest for normal, control monkeys and 1976 infarction lowest for infarcted monkeys breathing CO; CO exposure alone lowered fibrillation thresholds as did myocardial infarction; effects of CO and infarction together were additive
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5,000, 10,000 3 min, 6-12 NS Guinea pigs After immunization with sheep red blood cells, Snella and times per three of four exposure groups had increased Rylander 1979 day for 3-4 numbers of pulmonary alveolar macrophages, wk and all had increased polymorphonuclear leukocytes; reduced numbers of plaque forming cells in spleen and lungs 50 6 wk NS 15 dogs Pathologic electrocardiograms in 10 dogs, Lindenberg et al. pathology of heart in 7 dogs, and pathology of 1962 brain in 6 dogs 100 6 wk NS Dogs Pathologic changes in heart and brain Lindenberg et al.
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From page 86... ...
wk and with noninfarcted animals exposed to CO displayed 1973 myocardial increased P-wave amplitudes; a greater degree infarction of myocardial ischemia, signified by higher incidence of T-wave inversion, observed in infarcted animals exposed to CO Up to 462 12 h/d for 14 ~20 Female monkeys, No myocardial infarctions observed; no Malinow et al. mon standard or differences in plasma cholesterol or aortic or 1976 cholesterol added coronary atherosclerosis could be attributed to diet exposure Abbreviations: COHb, carboxyhemoglobin; d, day; h, hour; LC50, concentration lethal to 50% of subjects; min, minute; month, mon; NS, not stated; ppm, parts per million.
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From page 87... ...
Four dogs exposed to CO at 100 ppm for 5.75 h per day, 6 days per week for 11 weeks showed electrocardiographic changes, degenerative changes in heart muscle fibers, and histopathologic damage to the brain (Lewey and Drabkin 1944)
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From page 88... ...
exposed one group of guinea pigs to CO at 5,000 ppm and three groups of guinea pigs to CO at 10,000 ppm for 3 min, 6 or 12 times per day for 3-4 weeks. The animals were injected with sheep red blood cells one week prior to cessation of exposure and sacrifice.
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From page 89... ...
CO diffuses across the alveolar-capillary membrane, through plasma, across the red blood cell membranes, and finally into the red blood cell stroma to bind to hemoglobin. Because of the rapid binding of CO with hemoglobin in the red blood cells, there is a high pressure differential between red blood cells and air, favoring rapid diffusion of CO into blood.
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. INHALATION EXPOSURE LEVELS FROM THE NRC AND OTHER ORGANIZATIONS A number of organizations have established or proposed inhalation exposure limits or guidelines for CO.
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27 a The comparability of EEGLs and CEGLs with occupational and public health standards or guidance levels is discussed in Chapter 1, section "Comparison to Other Regulatory Standards or Guidance Levels." Abbreviations: ACGIH, American Conference of Governmental Industrial Hygienists; AEGL, acute exposure guideline level; CEGL, continuous exposure guidance level; EEGL, emergency exposure guidance level; h, hour; NAC, National Advisory Committee; NASA, National Aeronautics and Space Administration; NIOSH, National Institute for Occupational Safety and Health; NR, not recommended; NRC, National Research Council; OSHA, Occupational Safety and Health Administration; PEL, permissable exposure limit; REL, recommended exposure limit; SEAL, submarine escape action level; SMAC, spacecraft maximum allowable concentration; TLV, Threshold Limit Value; TWA, time-weighted average.
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From page 92... ...
NRC Recommended Exposure Level Current Proposed Values (ppm) EEGL 1h 400 55 180 24 h 50 20 45 CEGL 90 days 20 10 9 Abbreviations: CEGL, continuous exposure guidance level; EEGL, emergency exposure guidance level; h, hour; NRC, National Research Council; ppm, parts per million.
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From page 93... ...
. The subcommittee acknowledges that the experimental human literature on the acute effects of CO exposures includes a number of studies that report subtle deficits in visual detection thresholds and impaired performance on vigilance, time-estimation, and driving performance tasks at low COHb concentrations (MacFarland et al.
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From page 94... ...
DATA ADEQUACY AND RESEARCH NEEDS Although the literature on the effects of CO exposures in humans and animals is extensive, a number of data gaps remain. The conflicting results of studies on the neurobehavioral and cardiovascular effects of low-level CO exposures are of concern for submariners.
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From page 95... ...
Adjustments to the EEGL and CEGL values may be required when oxygen concentrations are outside the range cited above. REFERENCES ACGIH (American Conference of Governmental Industrial Hygienists)
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From page 96... ...
Presentation at the First Meeting on Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants, January 23, 2003, Washington, DC. Davies, D.M., and D.J.
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2000. History, pathophysiology, clinical presentation and role of hyperbaric oxygen in acute carbon monoxide poisoning.
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Presentation at the First Meeting on Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants, January 23, 2003, Washington, DC. Hassan, M.S., J
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Pp. 17-38 in Emer gency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants, Vol.
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2000. Carbon monoxide poisoning -- a public health perspective.
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1985. The relationship between exposure duration, carboxyhemoglobin, blood glucose, pyruvate and lactate and the severity of intoxication in 39 cases of acute carbon monoxide poisoning in man.
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1979. Effect of prolonged exposure to elevated carbon monoxide and carbon dioxide levels on red blood cell parameters during submarine patrols.
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