ACETONE 11 2. HEALTH EFFECTS 2.1 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 of the toxicology of acetone. 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. A glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile. 2.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE To help public health professionals and others address the needs of persons living or working near hazardous waste sites, the information in this section is organized first by route of exposure - inhalation, oral, and dermal; and then by health effect - death, systemic, immunological, neurological, reproductive, developmental, genotoxic, and carcinogenic effects. These data are discussed in terms of three exposure periods - acute (14 days or less), intermediate (15-364 days), and chronic (365 days or more). Levels of significant exposure for each route and duration are presented in tables and illustrated in figures. The points in the figures showing no-observed-adverse-effect levels (NOAELs) or lowest- observed- adverse-effect levels (LOAELs) reflect the actual doses (levels of exposure) used in the studies. LOAEL have been classified into less serious or serious effects. Serious effects are those that evoke failure in a biological system and can lead to morbidity or mortality (e.g., acute respiratory distress or death). Less serious effects are those that are not expected to cause significant dysfunction or death, or those whose significance to the organism is not entirely clear. ATSDR acknowledges that a considerable amount of judgment may be required in establishing whether an end point should be classified as a NOAEL, less serious LOAEL, or serious LOAEL, and that in some cases, there will be insufficient data to decide whether the effect is indicative of significant dysfunction. However, the Agency has established guidelines and policies that are used to classify ACETONE 12 2. HEALTH EFFECTS these end points. ATSDR believes that there is sufficient merit in this approach to warrant an attempt at distinguishing between less serious and serious effects. The distinction between less serious effects and serious effects is considered to be important because it helps the users of the profiles to identify levels of exposure at which major health effects start to appear. LOAELs or NOAELs should also help in determining whether or not the effects vary with dose and/or duration, and place into perspective the possible significance of these effects to human health. The significance of the exposure levels shown in the Levels of Significant Exposure (LSE) tables and figures may differ depending on the users perspective. Public health officials and others concerned with appropriate actions to take at hazardous waste sites may want information on levels of exposure associated with more subtle effects in humans or animals (LOAELs) or exposure levels below which no adverse effects (NOAELs) have been observed. Estimates of levels posing minimal risk to humans (Minimal Risk Levels or MRLs) may be of interest to health professionals and citizens alike. Estimates of exposure levels posing minimal risk to humans (Minimal Risk Levels or MRLs) have been made for acetone. An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncarcinogenic) over a specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration within a given route of exposure. MRLs are based on noncancerous health effects only and do not consider carcinogenic effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for inhalation and oral routes. Appropriate methodology does not exist to develop MRLs for dermal exposure. Although methods have been established to derive these levels (Barnes and Dourson 1988; EPA 1989a), uncertainties are associated with these techniques. Furthermore, ATSDR acknowledges additional uncertainties inherent in the application of the procedures to derive less than lifetime MRLs. As an example, acute inhalation MRLs may not be protective for health effects that are delayed in development or are acquired following repeated acute insults, such as hypersensitivity reactions, asthma, or chronic bronchitis. As these kinds of health effects data become available and methods to assess levels of significant human exposure improve, these MRLs will be revised. A Users Guide has been provided at the end of this profile (see Appendix A). This guide should aid in the interpretation of the tables and figures for Levels of Significant Exposure and the MRLs. ACETONE 13 2. HEALTH EFFECTS 2.2.1 Inhalation Exposure 2.2.1.1 Death In a retrospective mortality study of 948 employees (697 men, 251 women) of a cellulose fiber plant where acetone was used as the only solvent, no significant excess risk of death from any cause (all causes, malignant neoplasm, circulatory system disease, ischemic heart disease) compared with rates for the U.S. general population was found (Ott et al. 1983a, 1983b). The workers had been employed at the plant for at least 3 months to 23 years. Industrial hygiene surveys found that median time-weighted- average acetone concentrations were 380, 770, and 1,070 ppm based on job categories. As shown in Table 2-l and Figure 2-1, high concentrations of acetone were required to produce death in animals. An 8-hour LC 50 value of 21,091 ppm and a 4-hour LC 50 value of 31,994 ppm were found for female rats (Pozzani et al. 1959). Inhalation exposure to acetone for a few hours has resulted in death in rats at concentrations ranging from 16, inhalation exposure to acetone for a few hours has resulted in death in rats at concentrations ranging from 16,000 to 50,600 ppm (Bruckner and Peterson 1981a; Smyth et al. 1962) and in guinea pigs from 10,000 to 50,000 ppm (Specht et al. 1939). In general, higher concentrations of acetone resulted in death sooner than lower concentrations. That very high concentrations of acetone are required to cause death of animals is reinforced by the fact that no deaths were reported for rats exposed to acetone at 4,210 for 8 hours to 126-129 ppm for 25 minutes (Haggard et al. 1944) or mice exposed to <84,194 ppm for 8 hours (Mashbitz et al. 1936). No studies were located regarding death of animals after intermediate- or chronic-duration inhalation exposure to acetone. 2.2.1.2 Systemic Effects The systemic effects of inhalation exposure to acetone in humans and animals are discussed below. The highest NOAEL values and all LOAEL values for each systemic effect from each reliable study are recorded in Table 2-l and plotted in Figure 2-l. Respiratory Effects. The only effect on the respiratory system observed in humans exposed to acetone vapors is irritation of the nose, throat, trachea, and lungs. The irritating properties of acetone in humans have been noted both in workers who were exposed to acetone occupationally (Raleigh and ACETONE 24 2. HEALTH EFFECTS McGee 1972; Ross 1973) and in volunteers under controlled laboratory conditions (Matsushita et al. 1969a, 1969b; Nelson et al. 1943). Complaints of irritation were reported by workers with average exposures to acetone in the workroom of 901 ppm (Raleigh and McGee 1972; Ross 1973). In controlled situations, the volunteers had been asked to give their subjective complaints, and some of the volunteers reported that exposure to 100 ppm for 6 hours was irritating, with more subjects reporting irritation at increasing exposure levels (Matsushita et al. 1969b). Subjective symptoms also included the loss of the ability to smell acetone as exposure proceeded. In another controlled experiment, the majority of subjects, although exposed for only 3-5 minutes, estimated that they could tolerate an exposure level of 200 ppm for an 8-hour workshift (Nelson et al. 1943). Pulmonary function testing of volunteers exposed <1,250 ppm acetone intermittently for various durations in a complex protocol revealed no abnormalities caused by the exposure (Stewart et al. 1975). The volunteers did experience throat irritation sporadically. Exposure of animals to much higher concentrations of acetone than those reported in humans has resulted in respiratory effects. Pulmonary congestion, edema, and hemorrhage of the lungs were observed in guinea pigs that died after exposure to 10,000 ppm continuously for 1 or 2 days, to 20,000 ppm continuously for 1 day, or to 50,000 ppm for a few hours (Specht et al. 1939). The congestion and edema were attributed to the irritating effects of acetone on the mucosa. The hemorrhage may have been a consequence of death. Respiratory rates also decreased in the guinea pigs during exposures, but the decrease was probably a consequence of the narcotic effects of acetone (see Section 2.2.1.4). In mice exposed to acetone for 10 minutes, the calculated concentration of acetone that decreased the respiratory rate 50% (RC 50 ) was 77,516 ppm (Kane et al. 1980). The decrease in respiratory rate was considered to be due to sensory irritation, but adaptation to the irritant properties developed. The RC 50 for acetone was higher than the values calculated for other solvents, indicating that acetone is a weak irritant. In mice exposed to 6,000 ppm acetone for 0.5 hours/day for 1 or 5 days, no effects on the time of inspiration, time of expiration, time between breaths, or tidal volume were found (Schaper and Brost 1991). In addition, acetone exposure caused no changes in lung weight, lung volume displacement, or histological evidence of pulmonary pathology. Histological examination of the lungs of rats exposed intermittently to a high concentration of acetone (19,000 ppm) for 2-8 weeks revealed no evidence of treatment-related lesions (Bruckner and Peterson 1981b). ACETONE 25 2. HEALTH EFFECTS Cardiovascular Effects. Information regarding cardiovascular effects in humans following inhalation exposure to acetone is limited. High pulse rates (120-160/minute) were commonly found in patients exposed to acetone by inhalation and/or dermally after application of casts for which acetone was used in the setting solution (Chatterton and Elliott 1946; Hift and Pate1 1961; Pomerantz 1950; Renshaw and Mitchell 1956). In a controlled laboratory study using a complex protocol, electrocardiography of volunteers exposed to <1,250 ppm acetone intermittently for various durations revealed no alterations, compared with their preexposure electrocardiograms (Stewart et al. 1975). A retrospective mortality study of 948 workers (697 men, 251 women) employed for at least 3 months to 23 years at a cellulose fiber plant where acetone was used as the only solvent found no significant excess risk of death from circulatory system disease or ischemic heart disease compared with rates for the U.S. general population (Ott et al. 1983a, 1983b). Industrial hygiene surveys found that median time-weighted-average acetone concentrations were 380,770, and 1,070 ppm based on job categories. Reduced heart rates were observed in guinea pigs exposed to various high concentrations of acetone for various acute durations (Specht et al. 1939), but were probably a consequence of the narcotic effects of acetone (Section 2.2.1.4). Necropsy of the guinea pigs revealed no effects on the heart, but histological examination was not performed. Histological examination of the hearts of rats exposed intermittently to a high concentration of acetone (19,000 ppm) for 2-8 weeks revealed no evidence of treatment-related lesions (Bruckner and Peterson 1981b). Gastrointestinal Effects. Case reports have described vomiting of blood and gastrointestinal hemorrhage in patients who had hip casts applied with acetone present in the setting fluid (Chatterton and Elliott 1946; Fitzpatrick and Claire 1947; Harris and Jackson 1952; Hift and Pate1 1961; Pomerantz 1950; Renshaw and Mitchell 1956; Strong 1944). As the vomitus contained blood several hours after vomiting first commenced, the gastrointestinal hemorrhage may have been due to the trauma of repeated vomiting. These patients had a strong odor of acetone in their breath, and acetone was detected in the urine and blood. These patients were exposed to acetone by inhalation during cast application and from evaporation from the casts after the applications. In addition, the possibility of contribution from dermal exposure could not be ruled out. In one case, exposure was considered to be mainly dermal (Hift and Pate1 1961). ACETONE 26 2. HEALTH EFFECTS Necropsy of guinea pigs that died after exposure to various high concentrations of acetone for various acute durations revealed no effects on the stomach (Specht et al. 1939), but histological examination was not performed. Hematological Effects. In a health evaluation survey of 168 men and 77 women employed at a cellulose fiber production plant where acetone was used as the only solvent, all hematological parameters were within normal limits (Ott et al. 1983a, 1983c). The workers had been employed at the plant for at least 3 months to 23 years. Industrial hygiene surveys found median time-weighted- average acetone concentrations of 380, 770, and 1,070 ppm, based on job categories. Hematological effects have been observed in humans after inhalation exposure to acetone in controlled laboratory studies of volunteers. Statistically significant increased white blood cell counts and decreased phagocytic activity of neutrophils, compared with controls, were observed in the volunteers after a 6-hour exposure or repeated 6-hour exposures for 6 days to 500 ppm (Matsushita et al. 1969a, 1969b). No significant difference was seen in hematological parameters in the volunteers exposed to 250 ppm compared with controls. In contrast, hematological findings were within normal limits in volunteers exposed to 500 ppm for 2 hours (DiVincenzo et al. 1973) or <1,250 ppm acetone repeatedly for l-7.5 hours/day for as long as 6 weeks (Stewart et al. 1975). In animals, no studies were located regarding effects on the formed elements of the blood after inhalation exposure to acetone. Musculoskeletal Effects. No studies were located regarding musculoskeletal effects in humans or animals after inhalation exposure to acetone. Hepatic Effects. No indication that acetone caused hepatic effects in humans was found in controlled studies of volunteers. Clinical chemistry parameters indicative of liver injury (e.g., serum alanine aminotransferase, aspartate aminotransferase, lactic dehydrogenase, alkaline phosphatase, ornithine carbamoyl transferase, cholesterol, triglycerides, bilirubin, lipids, etc.) were within normal limits in volunteers exposed to acetone at concentrations of 500 ppm for 2 hours (DiVincenzo et al. 1973) or 11,250 ppm intermittently for various durations (Stewart et al. 1975). In a health evaluation survey of 168 men and 77 women employed for at least 3 months to 23 years at a cellulose fiber production plant where acetone was used as the only solvent, all clinical blood chemistry parameters (aspartate aminotransferase, alanine aminotransferase, lactic dehydrogenase, alkaline phosphatase, total ACETONE 27 2. HEALTH EFFECTS bilirubin, and albumin) were within normal limits (Ott et al. 1983a, 1983c). Industrial hygiene surveys found median time-weighted-average acetone concentrations of 380, 770, and 1,070 ppm, based on job categories. Fatty deposits were found in the livers upon autopsy of guinea pigs that died after exposure to high concentrations of acetone for various acute durations (Specht et al. 1939). In contrast, intermittent exposure of rats to a high concentration of acetone (19,000 ppm) for 2-8 weeks did not produce signs of liver toxicity, assessed by the measurement of serum aspartate aminotransferase, lactic dehydrogenase, liver weights, and histological examination of the liver (Bruckner and Peterson 1981b). Inhalation exposure to acetone at lower concentrations does not appear to be toxic to the liver of animals; however, acetone potentiates the hepatotoxicity induced by some other chemicals (see Section 2.6). The mechanism by which acetone exerts the potentiation is through the induction or increased activity of liver microsomal monooxygenases, particularly enzymes associated with cytochrome P-450IIEl (see Sections 2.35 and 2.6). Most of the studies showing enzyme induction have been conducted by the oral route (see Section 2.2.2.2). In acute inhalation studies in rats, acetone exposure resulted in statistically significant increases in the liver concentration of cytochrome P-450, the activity of ethoxycoumarin O-deethylase (associated with P-450IIBl), and the activity of glutathione- S-transferase, and decreased the liver free glutathione content (Brondeau et al. 1989; Vainio and Zitting 1978). Induction of microsomal enzymes is considered a normal physiological response to xenobiotics, rather than an adverse effect. In a developmental study, mice exposed intermittently to 6,600 ppm acetone on gestational days 6-19 had significantly increased absolute and relative liver weights compared with controls (p<0.05) (NTP 1988). Increased liver weight is considered a sign of maternal toxicity in developmental studies. The increased liver weight could have been associated with enzyme induction. Renal Effects. No indication that acetone caused renal effects in humans was found in controlled studies of volunteers. Clinical blood chemistry parameters indicative of kidney injury (e.g., blood urea nitrogen, uric acid) and urinalysis parameters were within normal limits in volunteers exposed to acetone at concentrations of 500 ppm for 2 hours (DiVincenzo et al. 1973) or 1,250 ppm intermittently for various durations (Stewart et al. 1975). ACETONE 28 2. HEALTH EFFECTS The only indication that inhalation exposure to acetone causes renal effects in animals was the consistent finding of congestion or distention of renal tubules or glomeruli in guinea pigs that died after exposure to high concentrations of acetone for various acute durations (Specht et al. 1939). Rats exposed intermittently to 19,000 ppm for <8 weeks had significantly decreased kidney weights (p<0.0l) after 4 weeks of exposure compared with controls, but not after 2 or 8 weeks of exposure or at 2 weeks postexposure (Bruckner and Peterson 1981b). Blood urea nitrogen levels were not affected by acetone exposure, and no evidence of histological changes in the kidneys were found. In the absence of other evidence of renal toxicity, the sporadically reduced kidney weight cannot be considered an adverse effect. Derma/Ocular Effects. Eye irritation is a common complaint of workers exposed to acetone vapors occupationally (Raleigh and McGee 1972) and in volunteers exposed under controlled conditions (Matsushita et al. 1969a, 1969b; Nelson et al. 1943; Ross 1973). In a report of the experience at the Tennessee Eastman Corporation on acetone concentrations not associated with injury presented at the American Conference of Governmental Industrial Hygienists (ACGIH) Tenth Annual Meeting, it was noted that acetone is mildly irritating to the eyes at 2,000-3,000 ppm, with no irritation persisting after exposure ceases (Sallee and Sappington 1949). Lacrimation has also been observed in guinea pigs exposed to acetone vapors (Specht et al. 1939). Since eye irritation is due to direct contact of the eyes with the vapor rather than a true systemic effect of inhalation of the vapor, this and other dermal/ocular effects resulting from direct contact with acetone are discussed in Section 2.3.3. Other Systemic Effects. No studies were located regarding other systemic effects in humans after inhalation exposure to acetone. Other systemic effects observed in animals after inhalation exposure to acetone include body weight changes. In a developmental study, rats exposed to acetone at 11,000 ppm, but not mice exposed to 6,600 ppm, intermittently during gestation had significantly (p<0.05) reduced body weight gain from gestational day 14 onward and reduced extragestational body weight on gestational day 20 (NTP 1988). However, in a behavioral study, no effect on body weight gain was observed in female rats exposed to 16,000 ppm intermittently for 2 weeks (Goldberg et al. 1964). It is possible that the condition of pregnancy made the rats more susceptible to body weight reduction. In addition, marked congestion and hemorrhage of the spleen were observed upon autopsy of guinea pigs that died after ACETONE 29 2. HEALTH EFFECTS exposure to various high concentrations of acetone for various acute durations (Specht et al. 1939). These effects could have been the consequence of death. 2.2.1.3 Immunological Effects The only information regarding immunological effects in humans after inhalation exposure to acetone is the finding of statistically significant increased white blood cell counts, increased eosinophil counts, and decreased phagocytic activity of neutrophils in volunteers exposed to 500 ppm for a single 6-hour exposure or intermittently for 6 days (Matsushita et al. 1969a, 1969b). No significant difference in these parameters was seen in the volunteers exposed to 250 ppm compared with controls. Hematological parameters, including total white cell counts and differential white cell counts, were within normal limits in other volunteers exposed to 500 ppm for 2 hours (DiVincenzo et al. 1973) or <1,250 ppm acetone intermittently for durations in a study with a complex protocol (Stewart et al. 1975); however, these investigators did not examine the phagocytic activity of neutrophils. The NOAEL value of 250 ppm and LOAEL value of 500 ppm are recorded in Table 2-l and plotted in Figure 2- 1. No studies were located regarding immunological effects in animals after inhalation exposure to acetone. 2.2.1.4 Neurological Effects Case reports have described patients who became comatose or collapsed after hip casts were applied with acetone present in the setting fluid (Chatterton and Elliott 1946; Fitzpatrick and Claire 1947; Harris and Jackson 1952; Renshaw and Mitchell 1956; Strong 1944). In addition, a woman experienced headache, dizziness, weakness, difficulty speaking, and depression after a cast containing acetone had been applied (Pomerantz 1950). These patients had a strong odor of acetone in their breath, and acetone was detected in the urine and blood. These patients were exposed to acetone by inhalation during cast application and from evaporation from the casts after the applications. In addition, the possibility of contribution from dermal exposure could not be ruled out. In another case of neurological effects (drowsiness, fretfulness, irritability, restlessness, uncoordinated hand movement, nystagmus) developing after application of a cast, exposure was considered to be mainly dermal because an airblower was used continuously during the application to dissipate the fumes (Hift and ACETONE 30 2. HEALTH EFFECTS Pate1 1961). However, because the patient had kept his head under a blanket, some inhalation of acetone evaporating from the cast may have occurred. Workers exposed to acetone in the past commonly experienced neurological effects. In an on-site medical appraisal of nine workers, in which the time-weighted average exposure concentration was 1,006 ppm, three of the workers mentioned headache and lightheadedness as subjective symptoms (Raleigh and McGee 1972). In another on-site medical appraisal of four workers, in which the time- weighted average exposure concentration was 901 ppm, none of the workers complained of neurological effects (Raleigh and McGee 1972). The medical examinations included the Romberg test, finger-to-nose test, and observations for nystagmus (involuntary rapid movement of the eyeball). These tests revealed no neurobehavioral effects in either study. Such symptoms as unconsciousness, dizziness, unsteadiness, confusion, and headache were experienced by seven workers exposed to >12,000 ppm acetone while cleaning out a pit containing acetone, that had escaped from nearby tanks (Ross 1973). The degree of the symptoms varied depending on the length of time that the workers had spent in the pit (2 minutes to 4 hours). Neurological and behavioral effects have also been documented in volunteers tested under controlled laboratory conditions. These effects included general lack of energy and weakness, headache, delayed visual reaction time (Matsushita et al. 1969a, 1969b); subjective symptoms of tension, tiredness, complaints (not otherwise specified), and annoyance (Seeber and Kiesswetter 1991; Seeber et al. 1992); increases in response and the percent false negatives in auditory discrimination tests and increases in anger and hostility (Dick et al. 1989); and increased visual evoked response (Stewart et al. 1975). Other neurological and neurobehavioral tests (e.g., electroencephalography, choice reaction time, visual vigilance, dual task, memory scanning, postural sway, Romberg test, or heel-to-toe test) were also conducted on these volunteers, but acetone exposure had no effect on these parameters. The relationship between concentration and duration of exposure on the development of narcosis was demonstrated in volunteers exposed to acetone at 21,049-84,194 ppm for 1-8 hours (Haggard et al. 1944). As the concentration increased, the time to observations of signs of narcosis (not otherwise described), loss of righting reflex, and loss of cornea1 reflex decreased. It should be noted that these concentrations of acetone are extremely high, and exposure to lower concentrations of acetone for shorter durations has resulted in unconsciousness in some workers, as discussed above. Based on a LOAEL of 237 ppm for 4 hours for neurobehavioral effects in humans (Dick et al. 1989), an acute inhalation MRL of 26 ppm was calculated as described in footnote b in Table 2-l. Based on a ACETONE 31 2. HEALTH EFFECTS LOAEL of 1,250 ppm for neurological effects in a 6-week study (Stewart et al. 1975), intermediate and chronic inhalation MRLs of 13 ppm were calculated as described in footnote c in Table 2-l. Narcotic effects have been observed in animals exposed acutely to acetone vapors. The narcotic effects observed in animals after inhalation exposure to acetone depend upon the duration and the magnitude of exposure. The narcotic effects appear to proceed through several stages: drowsiness, incoordination, loss of autonomic reflexes, unconsciousness, respiratory failure, and death as concentrations and durations increase. The acute data suggest that concentrations >8,000 ppm generally are required to elicit overt signs of narcosis, although neurobehavioral effects, when assessed by specific behavioral tests, have been observed at lower concentrations. The relationship between concentration and duration of exposure on the development of narcosis was demonstrated in rats exposed to acetone at 2,105-126,291 ppm for 5 minutes to 8 hours (Haggard et al. 1944). While exposure to 2,105 or 4,210 ppm for 8 hours resulted in no signs of narcosis or effects on righting reflex or cornea1 reflex, these effects were observed at higher concentrations. At increasing concentrations >10,524 ppm, the time to observations of signs of narcosis, loss of righting reflex, and loss of cornea1 reflex decreased. The responses were correlated with blood acetone levels. Similar concentration- and duration-response relationships were found in mice exposed to 16,839-84,194 ppm acetone for up to 4 hours (Mashbitz et al. 1936). Neurological responses included drowsiness, staggering, prostration, clonic movements of hind legs, and deep narcosis. Narcosis, evidenced by decreased respiratory and heart rates, paralysis, and coma were observed in guinea pigs exposed to 21,800 ppm continuously for periods ranging from 25 minutes to 24 hours (Specht et al. 1939). The degree of narcosis increased as the exposure duration increased. In a developmental study, virgin and pregnant mice experienced severe narcosis after a single 6-hour exposure to 11,000 ppm on the first day, but narcosis was no longer observed when the exposure was lowered to 6,600 ppm 6 hours/day for the rest of the study (NTP 1988). Neurobehavioral effects, indicative of narcosis, have been observed in rats, mice, and baboons acutely exposed to acetone vapors. These effects include central nervous system depression measured by five tests of unconditioned performance and reflex in rats (Bruckner and Peterson 1981a), decreased operant behavior evaluated by a multiple fixed ratio-fixed interval schedule of food reinforcement in rats (Geller et al. 1979b), inhibition of avoidance behavior and escape response in rats (Goldberg et al. 1964), decreased response to food presentation in mice (Glowa and Dews 1987), decreased duration of immobility in a behavioral despair swimming test in mice (DeCeaurriz et al. 1984), and incoordination ACETONE 32 2. HEALTH EFFECTS in a match to sample operant behavioral test in baboons (Geller et al. 1979a). In these studies, the animals recovered from the neurobehavioral effects as exposure continued, indicating adaptation or tolerance, or after exposure ceased, demonstrating the reversibility of these effects. The length of the recovery period was generally related to the level of exposure (Bruckner and Peterson 1981a; Glowa and Dews 1987). In the experiments of Geller et al. (1979a, 1979b), only four baboons and three rats were studied, precluding meaningful statistical analysis, and only two of the four baboons exhibited the effects. The rats were exposed to 150 ppm for 0.5-4 hours, and the baboons were exposed to 500 ppm continuously for 7 days. Intermediate-duration intermittent exposure of rats to 19,000 ppm acetone resulted in a statistically significant decrease (p<0.02) in absolute brain weight, but no exposure-related histological lesions (Bruckner and Peterson 1981b). Thus, based on the available data, the neurological effects of acetone are reversible and cannot be attributed to histologically observable changes in the brains of animals or to electroencephalographic changes in humans. The highest NOAEL values and the LOAEL values for neurological effects from each reliable study are recorded in Table 2-l and plotted in Figure 2- 1. 2.2.1.5 Reproductive Effects Information regarding reproductive effects in humans after inhalation exposure to.acetone is limited. Premature menstrual periods were reported by three of four women exposed to 1000 ppm acetone for 7.5 hours in a laboratory study of volunteers (Stewart et al. 1975). The shortening of the menstrual cycle was considered to be possibly due to the acetone exposure. Women workers in a Russian factory where workroom levels of acetone ranged from 14 to 126 ppm were reported to have statistically significantly increased incidences of pregnancy complications, including miscarriage, toxicosis (not otherwise described), decreased hemoglobin levels and hypotension, and weakness of labor activity, compared with controls (Nizyaeva 1982). However, the number of women studied, further description of the exposed and control groups (such as age, smoking history, use of alcohol), and description of workroom monitoring methods and statistical methods were not reported. Therefore, no conclusions can be made from this report. In a epidemiological study of the pregnancy outcome among 556 female laboratory workers, no statistically significant difference in the incidence of miscarriage was found between those exposed to a variety of solvents including acetone and those not exposed to solvents (Axelsson et al. 1984). ACETONE 33 2. HEALTH EFFECTS No reproductive effects (i.e., no effects on number of implants/litter, percent live pups/litter, or mean percent resorptions/litter) were observed in rats or mice in an inhalation developmental study (NTP 1988). No studies were located regarding reproductive effects in male animals, histological effects on reproductive organs of male or female animals, or the reproductive outcomes and other indices of reproductive toxicity in animals after inhalation exposure to acetone. The NOAEL values for reproductive effects in female rats and mice and the LOAEL value for premature menstrual periods in humans are recorded in Table 2-1 and plotted in Figure 2-1. 2.2.1.6 Developmental Effects Information regarding developmental effects in humans after inhalation exposure to acetone is limited. Statistically significant increased incidences of developmental effects, such as, intrauterine asphyxia of fetuses and decreased weight and length of neonates, were reported for women workers in a Russian factory, where workroom levels of acetone ranged from 14 to 126 ppm (Nizyaeva 1982). However, the number of women studied, further description of the exposed and control groups (such as age, smoking history, use of alcohol), and description of workroom monitoring methods and statistical methods were not reported. Therefore, no conclusions can be made from this report. In a epidemiological study of the pregnancy outcome among 556 female laboratory workers, no statistically significant differences in the incidences of miscarriage, perinatal death rate, or malformations were found between those exposed to a variety of solvents, including acetone, and those not exposed to solvents (Axelsson et al. 1984). In a development study in rats exposed intermittently to acetone during gestation, the only effect was a slight, but significant (p<0.05), decreased mean male and female fetal body weight at 11,000 ppm (NTP 1988). It should be noted that the dams exposed at this level had significantly (p<0.05) reduced body weight during gestation, reduced uterine weight, and reduced extragestational weight on gestational day 20. No effects were seen on sex ratio, incidence of fetal variations, reduced ossification sites, or mean fetal variations. The percent of litters with at least one fetal malformation was higher in the 11,000 ppm group than in the control group, but no statistically significant increased incidences of fetal malformations were observed. In mice similarly exposed during gestation, however, there was a slight, but significant (p<0.05) increase in percent late resorptions, decrease in mean male and female fetal weights, and increase in the incidence of reduced sternebral ossification in the 6,600 ppm group. The only evidence of maternal toxicity at this exposure level was statistically ACETONE 34 2. HEALTH EFFECTS significant increased absolute and relative liver weight. No effects were found on the number of implantations per litter, percent live fetuses/litter, sex ratio, incidence of malformations or skeletal variations combined. The NOAEL values and LOAEL values for developmental effects in rats and mice are recorded in Table 2- 1 and plotted in Figure 2-l. 2.2.1.7 Genotoxic Effects No studies were located regarding genotoxic effects in humans or animals after inhalation exposure to acetone. Genotoxicity studies are discussed in Section 2.4. 2.2.1.8 Cancer In a retrospective mortality study of 948 employees (697 men, 251 women) of a cellulose fiber plant where acetone was used as the only solvent, no significant excess risk of death from any cause, including malignant neoplasm, was found when compared with rates for the U.S. general population (Ott et al. 1983a, 1983b). The workers had been employed at the plant for at least 3 months to 23 years. Industrial hygiene surveys found that median time-weighted-average acetone concentrations were 380, 770, and 1,070 ppm, based on job categories. No studies were located regarding cancer in animals after inhalation exposure to acetone. 2.2.2 Oral Exposure 2.2.2.1 Death The 1991 Annual Report of the American Association of Poison Control Centers National Data Collection System documented 1,137 incidents of human exposure to acetone (Litovitz et al. 1992). Of these incidents, 1,124 were due to accidental or intentional ingestion (the others were not clearly specified). No fatalities were reported, only three cases had a major medical problem, 364 were treated in a health care facility, 233 cases were referred to hospitals but had no effects, 367 cases ACETONE 35 2. HEALTH EFFECTS suffered minor effects, and 39 suffered from moderate effects. None of the major, minor, or moderate effects were further described, and the outcomes of the remainder of the incidents were not reported. As seen in Table 2-2 and Figure 2-2, acute lethal dose (LD 50 ) values were located for rats, mice, and guinea pigs. In general, the lethality of acetone decreases with the age of the rats (Kimura et al. 1971). A higher LD 50 value was found for young adult rats than for older adult rats, but the difference was not statistically significant. Higher LD 50 values were found for Wistar rats (Smyth et al. 1962) and Nelson rats (Pozzani et al. 1959) than for Sprague-Dawley rats (Kimura et al. 1971). The LD 50 value determined by Freeman and Hayes (1985), who also used Sprague-Dawley rats, is in line with values for 14-day-old and young adult Sprague-Dawley rats. An oral LD 50 value of 5,250 mg/kg was found for male ddY mice (Tanii et al. 1986), and an oral LD 50 value of 3,687 mg/kg was found for male guinea pigs (Striegel and Carpenter 1961). In a study to determine which doses to use in a developmental study, oral dosing of pregnant mice with acetone during gestation resulted in the death of one of four mice at 2,400 mg/kg/day, and the number of dead mice increased as the dose increased (EHRT 1987). No controls were used in the range-finding study. One of two rabbits given 7,844 mg/kg acetone by gavage died within 19 hours of dosing, two rabbits given 5,491 mglkg survived, while one rabbit given 3,922 mg/kg died in 96 hours (Walton et al. 1928). Oral doses of 7,500 or 8,000 mg/kg acetone were fatal to two puppies (Albertoni 1884). No controls were included in these studies, and the small numbers of animals used limits the reliability of the findings. Signs of narcosis usually precede death in animals (see Section 2.2.2.4). No information was located regarding the doses of acetone that could result in increased mortality after intermediate- or chronic-duration exposure. 2.2.2.2 Systemic Effects No studies were located regarding respiratory, cardiovascular, hematological, musculoskeletal, hepatic, renal, or dermal/ocular effects in humans after oral exposure to acetone. The systemic effects in humans and animals after oral exposure to acetone are discussed below. The highest NOAEL values and the LOAEL values for each systemic effect from all reliable studies are recorded in Table 2-2 and plotted in Figure 2-2. Respiratory Effects. Oral exposure of animals to acetone has not been shown to produce adverse respiratory effects. However, microsomes from the lungs of hamsters exposed to acetone in drinking ACETONE 44 2. HEALTH EFFECTS water for 7 days had a 500% increased activity of aniline hydroxylase activity, an activity associated with cytochrome P-450IIEl (Ueng et al. 1991). Furthermore, the level of cytochrome P-45011El and the activity of butanol oxidase increased 6-fold in microsomes from the nasal mucosa of rabbits exposed to acetone in drinking water for 1 week (Ding and Coon 1990). Induction of microsomal enzymes is considered a normal physiological response to xenobiotics, rather than an adverse effect, unless accompanied by increased organ weight and histopathological or other adverse respiratory effects. Changes in respiratory rates (either increases or decreases), along with signs of narcosis, were observed in rabbits dosed with >3,922 mg/kg acetone (Walton et al. 1928), and irregular respiration, along with signs of narcosis, was observed in dogs dosed with 4,000 mg/kg (Albertoni 1884). In a range-finding study to determine which doses to use in a developmental study, mice that died at doses >4,800 mg/kg/day for 10 days displayed wheezing and/or rapid and labored breathing, accompanied by signs of severe narcosis, prior to death (EHRT 1987). However, the apparent respiratory effects probably reflect the severely compromised condition of these animals, rather than a toxic effect of acetone on the lungs. Gross necropsy of a dog dosed with 8,000 mg/kg acetone revealed no effects on the lungs, but the lungs were not examined histologically (Albertoni 1884). Histological examination of the lungs of rats and mice exposed to acetone in drinking water for 13 weeks (Dietz et al. 1991; NTP 1991) or of rats given acetone in water by gavage for 13 weeks (American Biogenics Corp. 1986) revealed no treatment related lesions. Thus, acetone by itself apparently is not toxic to the lungs of animals when administered by the oral route, but the induction of lung microsomal enzymes suggests that acetone may potentiate the respiratory effects induced by other chemicals (see Section 2.6). Cardiovascular Effects. Oral exposure of animals to acetone has not resulted in adverse effects on the heart in intermediate-duration studies. Histological examination of the hearts of rats and mice exposed to acetone in drinking water for 13 weeks (Dietz et al. 1991; NTP 1991) or of rats given acetone in water by gavage for 13 weeks (American Biogenics Corp. 1986) did not reveal treatment- related lesions. However, the heart-to-brain weight ratio was significantly increased (p<0.01) in the female rats treated by gavage with 2,500 mg/kg/day. In the absence of histologically observable lesions, the toxicological significance of the increased heart weight is questionable. Gastrointestinal Effects. No studies were located regarding gastrointestinal effects per se in humans after oral exposure to acetone, but a man who intentionally drank 200 mL of pure acetone ACETONE 45 2. HEALTH EFFECTS (2,241 mg/kg) had a red and swollen throat and erosions in the soft palate and entrance to the esophagus (Gitelson et al. 1966). Significantly increased levels of cytochrome P-450IAl in duodenal microsomes and P-450IIB2 in duodenal and jejunal microsomes from rats exposed to acetone in drinking water for 3 days were found (Carriere et al. 1992). No increase in cytochrome P-450IIEl was found in these microsomal preparations. As discussed above for respiratory effects, induction of microsomal enzymes is considered a normal physiological response to xenobiotics rather than an adverse effect. Oral exposure of animals to acetone has not resulted in adverse effects on the gastrointestinal tract in intermediate- duration studies. Histological examination of the gastrointestinal tract of rats and mice exposed to acetone in drinking water for 13 weeks (Dietz et al. 1991; NTP 1991) or of rats given acetone in water by gavage for 13 weeks (American Biogenics Corp. 1986) did not reveal treatment-related lesions. Hematological Effects. Exposure of rabbits to 863 mg/kg/day acetone in the drinking water for 7 days resulted in a 12.9-fold increase in the levels of cytochrome P-45011El in bone marrow microsomes (Schnier et al. 1989). As discussed for respiratory effects, induction of microsomal enzymes is considered a normal physiological response to xenobiotics rather than an adverse effect. Hematological effects of oral exposure to acetone have been observed in rats but not in mice. Bone marrow hypoplasia was observed in five of five male rats exposed to acetone in the drinking water for 14 days at 6,942 mg/kg/day, but not at 4,312 mg/kg/day (Dietz et al. 1991; NTP 1991). None of the female rats had bone marrow hypoplasia. Although mice were similarly treated for 14 days in this study, the authors did not specify whether bone marrow was examined; however, in the 13-week studies, no hematological effects or histologically observable lesions in hematopoietic tissues were found in mice. In contrast, evidence of macrocytic anemia was found in male rats exposed to acetone in drinking water for 13 weeks. This evidence consisted of significantly (p<0.05 or p<0.01) decreased hemoglobin concentration, increased mean corpuscular hemoglobin and mean corpuscular volume, decreased erythrocyte counts, decreased reticulocyte counts and platelets, and splenic hemosiderosis. The LOAEL for these effects was 400 mg/kg/day, and the NOAEL was 200 mg/kg/day. The number of affected parameters increased as the dose increased. Based on the NOAEL of 200 mg/kg/day for macrocytic anemia, an intermediate oral MRL of 2 mg/kg/day was calculated as described in the footnote in Table 2-2. In female rats, hematological effects consisted of statistically significant increased lymphocyte counts, increased mean corpuscular hemoglobin and mean corpuscular volume at the highest dose, and decreased platelets at the highest and next-to-highest dose levels (Dietz et al. ACETONE 46 2. HEALTH EFFECTS 1991; NTP 1991). The biological significance of the hematological effects in female rats was not clear, but the effects were not consistent with anemia. Sex differences in the hematological effects of acetone exposure were also found in rats treated by gavage (American Biogenics Corp. 1986). Gavage treatment for 46-47 days significantly (p<0.01) increased hemoglobin, hematocrit, and mean cell volume in high-dose males (2,500 mg/kg/day), but not in females. With longer duration treatment (13 weeks), both high-dose males (p<0.01) and females (p<0.05) had increased hemoglobin and hematocrit, and high-dose males (p<0.01) also had increased mean cell hemoglobin and mean cell volume and decreased platelets. Thus, it appears that species and sex differences exist for hematological effects of oral exposure to acetone. Musculoskeletal Effects. Histological examination of femurs of rats and mice exposed to acetone in drinking water for 13 weeks (Dietz et al. 1991; NTP 1991) or of rats given acetone in water by gavage for 13 weeks (American Biogenics Corp. 1986) did not reveal treatment-related lesions. Skeletal muscle was not examined histologically in the 13-week drinking water study (Dietz et al. 1991; NTP 1991), but histological examination of the skeletal muscle in rats in the 13-week gavage study did not reveal treatment-related lesions (American Biogenics Corp. 1986). Based on this limited information, it appears that acetone does not produce musculoskeletal effects. Hepatic Effects. Acetone by itself is moderately toxic to the liver of animals, but acetone potentiates the hepatotoxicity of some other chemicals by inducing microsomal enzymes that metabolize other chemicals to reactive intermediates (see Sections 2.3.5 and 2.6). Numerous studies have investigated these mechanisms to identify the specific cytochrome P-450 isoenzymes involved (Banhegyi et al. 1988; Barnett et al. 1992; Carriere et al. 1992; Chieli et al. 1990; Furner et al. 1972; Gervasi et al. 1991; Hetu and Joly 1988; Hewitt et al. 1987; Hong et al. 1987; Hyland et al. 1992; Johannson et al. 1988; Kinsler et al. 1990; Kobusch et al. 1989; Koop et al. 1989, 1991; Menicagli et al. 1990; Porter et al. 1989; Puccini et al. 1989, 1990, 1992; Puntarulo and Cederbaum 1988; Robinson et al. 1989; Ronis et al. 1991; Ronis and Ingelman-Sundberg 1989; Schnier et al. 1989; Sipes et al. 1973; Song et al. 1989; Tu et al. 1983; Ueng et al. 1991; Yoo and Yang 1985). In these studies in general, rats, mice, rabbits, or hamsters were given acetone by gavage in water or in drinking water for 1 day to 2 weeks. Microsome preparations from the livers were then analyzed for cytochrome P-450 content, enzyme activities associated with specific cytochrome P-450 isoenzymes (particularly cytochrome P-450IIEl), and identification of the specific isoenzymes. Acetone has also been shown to increase the activity of glutathione S-transferase (Sippel et al. 1991). These topics are ACETONE 47 2. HEALTH EFFECTS discussed more fully in Sections 2.35 and 2.6. Induction of microsomal enzymes is considered a normal physiological response to xenobiotics rather than an adverse effect, unless it is accompanied by increased liver weight and other hepatic effects. Mice exposed to acetone in drinking water for 14 days had dose-related increased liver weights at 965 mg/kg/day, probably associated with microsomal enzyme induction (Dietz et al. 1991; NTP 1991). The increased liver weight was accompanied by hepatocellular hypertrophy at 23,896 mg/kg/day. In rats treated for 14 days, increased liver weight was stated to occur at the same or lower doses as in the 13-week study (see below), but more definitive information regarding the doses was not provided. Histological examination revealed no treatment-related hepatic effects in rats. As stated above, acetone by itself is only moderately toxic to the liver. In mice exposed to 1,900 mg/kg/day acetone in the drinking water for 10 days, histological examination of the liver revealed no hepatic lesions (Jeffery et al. 1991). Acetone did not increase the level of serum alanine aminotransferase in rats at 871 mg/kg (Brown and Hewitt 1984), the levels of serum alanine aminotransferase or bilirubin at 1,177 mg/kg (Charbonneau et al. 1986b), or the activities of hepatic glucose-6-phosphatase, serum alanine aminotransferase, and serum ornithine carbamoyltransferase in rats given 1,961 mg/kg for 1 day or 392 mg/kg/day for 3 days (Plaa et al. 1982). However, in an intermediate-duration study, male rats, but not female rats, treated by gavage with 2,500 mg/kg/day, but not 500 mg/kg/day, for 46-47 days and for 13 weeks had statistically significant increased levels of serum alanine amino transferase (American Biogenics Corp. 1986). Liver weights were statistically significantly increased in female rats at 500 mg/kg/day, but not at 100 mg/kg/day, and in male rats at 2,500 mg/kg/day after 13 weeks, but organ weights were not measured in the rats treated for 46-47 days. In the 13-week drinking water study, liver weights were also significantly (p<0.01) increased in both sexes of rats at the same concentration (20,000 ppm, which was equivalent to 1,600 mg/kg/day for females, 1,700 mg/kg/day for males) and in female, but not male mice, at 11,298 mg/kg/day (Dietz et al. 1991; NTP 1991). However, in the mice, the increased liver weight was not associated with hepatocellular hypertrophy seen in the 14-day study, suggesting a development of tolerance. Taken together, the data indicate that acetone induces liver microsomal enzymes, increases liver weights, and may cause liver injury, as evidenced by increased serum levels of liver enzymes associated with liver injury and hepatocellular hypertrophy. Species and sex differences exist in susceptibility to acetone-induced liver effects. ACETONE 48 2. HEALTH EFFECTS Renal Effects. Acetone can also induce enzymes in microsomes prepared from kidneys. In hamsters given drinking water containing acetone for 7 days (Ueng et al. 1991) or 10 days (Menicagli et al. 1990), the microsomes prepared from kidneys had increased levels of cytochrome P-450 and cytochrome b 5 and/or statistically significantly increased activities of p-nitrophenol hydroxylase, aniline hydroxylase, and aminopyrine-N-demethylase. Microsomes prepared from kidneys of rats treated by gavage with acetone had increased levels of cytochrome P-450IIEl and increased activity of N-nitrosodimethylamine demethylase (Hong et al. 1987). Induction of microsomal enzymes is considered to represent a normal physiological response to xenobiotics rather than an adverse effect, unless accompanied by increased organ weight and other adverse renal effects. Oral exposure of rats and mice to acetone has resulted in effects on the kidney. Degeneration of the apical microvilli of renal tubules was reported in male rats after a single oral dose of acetone in corn oil, but not in corn oil treated controls (Brown and Hewitt 1984). The incidence of this lesion was not reported. However, in rats treated with 1,766 mg/kg/day acetone for 2 days, no significant difference was found for kidney weight, blood urea nitrogen (BUN) levels, or organic ion accumulation compared with controls (Valentovic et al. 1992). In 14-day drinking water studies, mice had doserelated increased kidney weights at >6,348 mg/kg/day (Dietz et al. 1991; NTP 1991). In rats treated for 16days, increased kidney weight occurred at the same or lower doses as in the 13-week study (see below), but more definitive information regarding the doses was not provided. Histological examination of the kidneys revealed no treatment-related lesions in rats or mice. In the intermediate-duration drinking water study, significantly (p<0.01) increased kidney weights were seen in female rats at 21,600 mg/kg/day and in male rats at 3,400 mg/kg/day (Dietz et al. 1991; NTP 1991). Conversely, male, but not female rats, given acetone in the drinking water at 21,700 mg/kg/day had increased incidence and severity of nephropathy that was not accompanied by hyaline droplet accumulation (Dietz et al. 1991; NTP 1991). In the 13-week gavage study, kidney weights were significantly (p<0.05 or p<0.01) increased in female rats at >500 mg/kg/day and in male rats at 2,500 mg/kg/day (American Biogenics Corp. 1986). In addition, renal proximal tubule degeneration and intracytoplasmic droplets of granules (hyaline droplets) in the proximal tubular epithelium were seen in both control and treated rats at similar incidence, but the severity of these lesions showed a dose-related increase in males at >500 mg/kg/day and in females at 2,500 mg/kg/day. The renal lesions seen in both the gavage study and the drinking water study may represent an enhancement by acetone of the nephropathy commonly seen in aging rats (American Biogenics Corp. ACETONE 49 2. HEALTH EFFECTS 1986; NTP 1991). No renal effects were observed in mice given acetone in the drinking water for 13 weeks (Dietz et al. 1991; NTP 1991). Thus, species differences exist in susceptibility to acetone-induced renal effects. Sex differences also exist, with kidney weight increases occurring in female rats at lower doses than in males rats, but histopathological lesions occurring in male rats at lower doses than in females. DermaVOcular Effects. No studies were located regarding dermal or ocular effects in humans after oral exposure to acetone. Histological examination of eyes and skin of rats and mice after exposure to drinking water containing acetone for 13 weeks at doses <3,400 mg/kg/day (rats) and 11,298 mg/kg/day (mice) revealed no treatment-related effects (Dietz et al. 1991; NTP 1991). Similarly, ophthalmoscopic examination of the eyes of rats treated by gavage with acetone at doses <2,500 mg/kg/day revealed no ocular lesions (American Biogenics Corp. 1986). Skin was not examined histologically in the gavage study. Other Systemic Effects. Acetone exposure of humans can result in diabetes-like symptoms, e.g., hyperglycemia and glycosuria. For example, a man who intentionally drank about 200 mL (about 2,241 mg/kg) of pure acetone had been treated at a hospital for acetone poisoning, but 4 weeks after the ingestion, he noticed excessive thirst and polyuria, and 2.5 months after ingestion, he was hyperglycemic (Gitelson et al. 1966). As discussed by Gitelson et al. (1966), hyperglycemia and glycosuria are commonly seen in cases of acetone poisoning. Most of the information regarding other systemic effects in animals after oral exposure to acetone relates to body weight changes. However, in an acute study conducted to determine the temporal effects of maintaining elevated plasma concentrations of acetone similar to those encountered in fasting and diabetic patients, treatment of rats by gavage with 3,214 mg/kg/day resulted in significantly reduced (p<0.01) insulin-stimulated glucose oxidation in adipose tissue (Skutches et al. 1990). The reduction was greater in fasted rats than in fed rats. Rats treated by gavage with a lethal dose of acetone (LD 50 = 5,800 mg/kg) lost 15% of their body weight until 48 hours after dosing (Freeman and Hayes 1985). However, treatment of rats by gavage with 1,766 mg/kg/day for 2 days (Valentovic et al. 1992) or with drinking water that provided lower doses (<1,200 mg/kg/day) for up to 2 weeks (Furner et al. 1972; Hetu and Joly 1988) did not affect body weight gain. Rats maintained on drinking ACETONE 50 2. HEALTH EFFECTS water for 14 days at higher doses displayed decreased body weight gain >l0% of controls, but the decrease was associated with reduced water consumption probably due to unpalatability (Dietz et al. 1991; NTP). In contrast, mice similarly treated had decreased water consumption at doses 6,348 mg/kg/day, but no effects on body weight gain occurred at doses <12,725 mg/kg/day. Maternal body weight was slightly (5%) but significantly (p=0.02) reduced on day 3 postpartum in mice treated with 3,500 mg/kg/day acetone by gavage during gestation (EHRT 1987). In intermediate-duration studies, gavage or drinking water treatment of rats or mice with acetone did not result in reductions in body weight except in cases where fluid consumption was reduced (American Biogenics Corp. 1986; Ladefoged et al. 1989; NTP 1991; Spencer et al. 1978). 2.2.2.3 Immunological Effects No studies were located regarding immunological effects in humans or animals after oral exposure to acetone. 2.2.2.4 Neurological Effects The narcotic effects of acetone occur after oral as well as inhalation exposure. Several case reports describe patients in minimally responsive, lethargic, or comatose conditions after ingesting acetone, but most of these cases are confounded by coexposure to other possible narcotic agents. For example, a 30-month-old child ingested most of a 6 ounce bottle of nail polish remover containing 65% acetone and 10% isopropyl alcohol (Gamis and Wasserman 1988); a known alcoholic woman ingested nail polish remover (Ramu et al. 1978); and a man ingested 200 mL of sake prior to intentionally ingesting liquid cement containing a mixture of polyvinyl chloride, acetone, 2-butanone, and cyclohexanone (Sakata et al. 1989). The lethargic and comatose condition of these patients were, however, attributed to acetone poisoning, although one case of coma was attributed primarily to cyclohexanol, the metabolite of cyclohexanone in the liquid cement (Sakata et al. 1989). Blood levels of acetone in some of these patients were 2.5 mg/mL (Ramu et al. 1978) and 4.45 mg/mL (Gamis and Wasserman 1988). In the case reported by Sakata et al. (1989), the blood level of acetone was 110