Final Report on the Safety Assessment of Glutaral

A new effect residual ratio (ERR) method for the validation of the concentration addition and independent action models

BACKGROUND, AIM, AND SCOPE

Glutaraldehyde (GA) often acts as an effective sterilant, disinfectant, and preservative in chemical products. It was found that GA had clearly acute toxicity to aquatic organisms. Furthermore, GA in natural environment could not exist as single species but as complex mixtures. To explore the toxicity interaction between GA and the other environmental pollutant, it is necessary to determine the mixture toxicities of various binary mixtures including GA. Two reference models, concentration addition (CA) and independent action (IA), are often employed to evaluate the mixture toxicity, which can be finished by comparing the concentration-response curves (CRCs) predicted by the reference models with the experimental CRC of the mixture. However, the CRC-based method cannot effectively denote the degree of the deviations from the reference models, especially at very low effect levels. Though the model deviation ratio (MDR) can be used to quantitatively evaluate the deviation of a mixture at EC50 level from the reference model, it is difficult to evaluate the deviations at the lower effect levels. Therefore, the primary aim of this study was to develop a new effect residual ratio (ERR) method to validate the deviations from the reference models at various effect levels.

MATERIALS AND METHODS

Four chemicals having possible dissimilar mode of actions with GA, acetonitrile (ACN), dodine (DOD), simetryn (SIM), and metham sodium (MET), were selected as another component in the binary mixtures including GA, which constructed four binary mixtures, GA-ACN, GA-DOD, GA-SIM, and GA-MET ones. For each binary mixture, two equipotent mixture rays where the concentration ratios of GA to another mixture component are respectively EC50 and EC5 ones were designed and their toxicities (expressed as a percent inhibition to Photobacterium phosphoreum) were determined by microplate toxicity analysis. The observed concentration-response curve (CRC) of a ray was compared with that predicted by CA or IA model to qualitatively assess the toxicity interaction of the mixture ray. To quantitatively and effectively examine the deviations at various effect levels from the reference models, a new concept, ERR at an effect, was defined, and the ERR was employed to evaluate the deviation at various effects with confidence intervals.

RESULTS

For three binary mixtures, GA-ACN, GA-DOD, and GA-SIM, the CRCs predicted by IA models were almost located in the 95% confidence intervals of the experimental CRCs for both equipotent mixture rays, which indicated the independent actions between binary mixture components. However, two rays of GA-MET binary mixture displayed a little synergistic action because both CRCs predicted by CA and IA were lower than the experimental CRC. ERR showed the same results as MDR, but ERR results at low effect area were clearer than MDR ones.

DISCUSSION

In CRC comparison, the deviation of CA (for GA-ACN, GA-DOD, and GA-SIM combinations) or IA (for GA-MET) model from the experimental values could be obviously observed at medium area of the CRC. However, at very low effect levels, both deviations of CA and IA and difference between CA and IA model predictions were not very apparent. Thus, it was difficult to confirm which model, CA or IA, had better predicted power at very low effect levels. MDR in many literatures often refers to a ratio at EC50 level. It was also difficult to reflect not only the deviation fact at the other ECx but also the deviation uncertainty. After we extended the definition of MDR to all ECx and examined the 95% confidence intervals based on observation, the plot of the redefined MDRs at many effect levels could better explain the deviations of CA or IA model from the observation. However, MDRs at very low effect levels did not still reflect the high uncertainty there. The ERRs defined in our paper could explicitly explain the degree of deviation from the reference models and especially reflect the high uncertainty at very low effects. It could be said that the ERR is a better indicator than MDR.

CONCLUSIONS

The new ERR validation method developed in our laboratory could provide us with the information about the toxicity interaction between the mixture components and quantitatively assess the accuracy of the reference models (CA or IA) at whole effect levels. The ERR method conquered the invalidation of the classical CRC comparison method on the deviation decision at low effect levels and also got the advantage over the MDR methods.

RECOMMENDATIONS AND PERSPECTIVES

It holds promise to become an effective method of hazard and risk assessments of chemical mixtures by well characterizing the uncertainty at very low effect levels.

Chronic toxicity and oncogenicity study with glutaraldehyde dosed in the drinking water of Fischer 344 rats

Glutaraldehyde (GA) has a wide spectrum of industrial, scientific and biomedical applications. Its potential to produce chronic toxic and/or oncogenic effects was investigated in Fischer 344 rats (100/sex/group) given GA in drinking water for a maximum of 104 weeks. GA concentrations were 0 (control), 50,250 and 1000 ppm, resulting in average daily GA consumptions, respectively, of 0, 4, 17 and 64 mg/kg for males and 0, 6, 25 and 86 mg/kg for females. Interim euthanasia (10/sex/group) was performed at 52 and 78 weeks. Parameters evaluated were clinical signs, body weight, food and water consumption, hematology, serum chemistry, urinalysis, organ weights, gross and microscopic pathology. There were no treatment-related effects on mortality. Absolute body weights and body weight gains of the 250 and 1000 ppm males and females were reduced over the study in a dosage-related manner. Food and water consumption by the 250 and 1000 ppm groups were decreased in a statistically significant dose-related manner over the study, and mean water consumption by the 50 ppm animals was slightly reduced but not with statistical significance. The 250 and 1000 ppm groups had a dose-related decrease in urine volume with increased osmolality, and pH was slightly reduced. Absolute kidney weights were increased in the 250 and 1000 ppm groups at the 52 and 78 week sacrifices, and decreased at 104 weeks. Relative kidney weights were increased at all sacrifice times for the 1000 ppm group, at 52 weeks for the 250 ppm group, and at 72 weeks for the 50 ppm group. The urinalysis and renal weight changes are compatible with a physiological compensatory adaptation to reduced water consumption. Gross and histological evidence for gastric irritation was observed principally in the 1000 ppm rats euthanized at 104 weeks and in animals that died during the study. Bone marrow hyperplasia and renal tubular pigmentation, seen in rats that died and the 104 week euthanasia animals, may have been secondary to a low grade hemolytic anemia in animals with large granular lymphocytic leukemia (LGLL). The only neoplasm that showed a statistically significant increase was LGLL, which occurred at a high incidence in both sexes and all groups, including the controls, for both animals that died and at the 104 week euthanasia. A few instances of LGLL were observed at 78 weeks. The overall incidence of LGLL in the spleen for the 0, 50, 250 and 1000 ppm groups was, respectively, 43, 51, 40 and 46% for males, and 24, 41, 41 and 53% for females. Statistical analyses indicated that the severity of LGLL was associated with the higher dosages of GA in female, but not male, rats. Due to the background and variable incidence of LGLL in the Fischer 344 rat, the finding of a statistical significance only for female rats, and because, there was no clear dose-response relationship, the biological significance of the LGLL findings is unclear. There is the possibility that the significance was a statistical artifact due to the low incidence of LGLL in the female control animals as a result of biological variability within the study. It is also considered to be possible that the chronic dosage of GA in the drinking water resulted in a modification of one or more of the factors responsible for the expression of this common and spontaneously occurring neoplasm in the Fischer 344 rat.

Toxicological, medical and industrial hygiene aspects of glutaraldehyde with particular reference to its biocidal use in cold sterilization procedures

Aqueous solutions of > or =5% glutaraldehyde (GA) are of moderate acute peroral toxicity and those of < or =2% are of slight toxicity. By single sustained skin contact, aqueous GA solutions of > or =45% are of moderate acute percutaneous toxicity, those of 25% are of slight toxicity and those of </=15% do not present an acute percutaneous hazard. Vapor generated at ambient temperature may cause sensory irritant effects to the eye and respiratory tract, but not acute respiratory tract injury. The 50% decrease in respiratory rate (rd(50)) is 13.86 ppm. A 0.1% solution of GA is not irritating to the eye; the threshold for conjunctival irritation is 0.2% and for corneal injury it is 1.0%. Eye injury is moderate at 2% and severe at > or =5%. Primary skin irritation depends on the duration and contact site, occlusion and solvent. By sustained contact, the threshold for skin irritation is 1%, above which erythema and edema are dose related. With 45% and higher, skin corrosion may occur. There is a low incidence of skin sensitizing reactions, with an eliciting threshold of 0.5% aqueous GA. However, GA is neither phototoxic nor photosensitizing. Subchronic repeated exposure studies by the peroral route show only renal physiological compensatory effects, secondary to reduced water consumption. Repeated skin contact shows only minor skin irritant effects without systemic toxicity. By subchronic vapor exposure, effects are limited to the nasal mucosa at 1.0 ppm, with a no-effect concentration generally at 0.1 ppm. There is no evidence for systemic target organ or tissue toxicity by subchronic repeated exposure by any route. A chronic drinking water study showed an apparent increase, in females only, of large granular cell lymphocytic leukemia but this was not dosage related. This is most likely the result of a modifying effect on the factor(s) responsible for the expression of this commonly occurring rat neoplasm. A chronic (2-year) inhalation toxicity/oncogenicity study showed inflammatory changes in the anterior nasal cavity but no neoplasms or systemic toxicity. In vitro genotoxicity studies--bacterial mutagenicity, forward gene mutation (HGPRT and TK loci), sister chromatid exchange, chromosome aberration, UDS and DNA repair tests--have given variable results, ranging from no effect through to weak positive. In vivo genotoxicity studies--micronucleus, chromosome aberration, dominant lethal and Drosophila tests--generally have shown no activity but one mouse intraperitoneal study showed bone marrow cell chromosome aberrations. Developmental toxicity studies show GA not to be teratogenic, and a two-generation study showed no adverse reproductive effects. Percutaneous pharmacokinetic studies showed low skin penetration, with lowest values measured in vitro in rats and human skin. Overexposure of humans produces typical sensory irritant effects on the eye, skin and respiratory tract. Some reports have described an asthmatic-like reaction by overexposure to GA vapor. In most cases this resembles reactive airways dysfunction syndrome, and the role of immune mechanisms is uncertain. Local mucosal effects may occur if medical instruments or endoscopes are not adequately decontaminated. Protection of individuals from the potential adverse effects of GA exposure requires that there be adequate protection of the skin, eyes and respiratory tract. The airborne concentration of GA vapor should be kept below the recommended safe exposure level (e.g. the threshold limit value) by the use of engineering controls. Those who work with GA should, through a training program, be aware of the properties of GA, its potential adverse effects, how to handle the material safely and how to deal with accidental situations involving GA. If effects develop in exposed workers, the reasons should be determined immediately and corrective methods initiated. (c) 2001 John Wiley & Sons, Ltd.