Two-generation reproduction toxicity study with isopropanol in rats

Scientific Opinion on Flavouring Group Evaluation 7, Revision 5 (FGE.07Rev5): saturated and unsaturated aliphatic secondary alcohols, ketones and esters of secondary alcohols and saturated linear or branched-chain carboxylic acids from chemical group 5

The EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids was requested to evaluate 53 flavouring substances attributed to the Flavouring Group Evaluation 07, including four new substances but-3-en-2-ol, non-1-en-e-ol, hex-1-en-3-one and 1-nonene-3-one [FL-nos: 02.131, 02.187, 07.161 and 07.210] in this Revision 5, using the Procedure in Commission Regulation (EC) No 1565/2000. None of the 53 substances was considered to have genotoxic potential. The substances were evaluated through a stepwise approach that integrates information on the structure-activity relationships, intake from current uses, toxicological threshold of concern (TTC), and available data on metabolism and toxicity. The Panel concluded that all 53 substances do not give rise to safety concerns at their levels of dietary intake, estimated on the basis of the 'Maximised Survey-derived Daily Intake' (MSDI) approach. Besides the safety assessment of the flavouring substances, the specifications for the materials of commerce have also been considered and found adequate. For 50 substances, further information is required based on comparison of the 'modified Theoretical Added Maximum Daily Intakes' (mTAMDIs) with the TTCs. This would include more reliable intake data and then, if required, additional toxicological data.

Exposure to multiple low-level chemicals in relation to reproductive hormones in premenopausal women involved in liquid crystal display manufacture

Background: Liquid crystal display (LCD) manufacturing involves three fabrication processes: array, panel and module processes, which result in different levels of volatile organic compound (VOC) exposure. The aim of this study was to assess the potential reproductive endocrine effects of occupational exposures during LCD manufacturing predictive of menstrual cycles as subclinical markers of female reproductive dysfunction effects of low-dose exposures. Methods: A total of 94 fabrication workers were followed for one complete menstrual cycle using daily urine samples: 23 were from the array, 53 from the panel, and 18 from the module work areas. The menstrual cycle characteristics of the study population were measured using a self-administered questionnaire. Urine samples were collected during the first urination in the morning for at least one complete menstrual cycle. The urine was then analyzed to determine the urinary concentrations of follicular stimulating hormone (FSH), estrone conjugates (E1C), and pregnanediol-3-glucuronide (PdG). The results of this analysis were used to assess the potential effects of chemical exposure as determined by handheld volatile organic compound (VOC) monitors and 24 h canisters. Results: The concentration of total VOCs was much higher in the module making area (ND–21,000 ppb) than in panel (ND–766 ppb) and array (58–1,472 ppb) making areas. The concentrations of ethanol and acetone were much higher in the module (1,974.9 and 2,283.2 ppb, respectively) and panel (2256.9 and 592.2 ppb, respectively) making areas. Compared to those in the array making area, we found that E1C (12.55, 95% confidence interval (CI): 8.49, 16.61 μg/mg Cr) and PdG (0.53, 95% CI: 0.29, 0.77 μg/mg Cr) levels in the module group were significantly higher in the early follicular phase; E1C (11.93, 95% CI: 6.21, 17.65 μg/mg Cr) and PdG (0.53, 95% CI: 0.29, 0.77 μg/mg Cr) levels were significantly higher in the periovulatory phase; and all the hormone levels, FSH (1.48, 95% CI: 0.81, 2.15 μg/mg Cr), E1C (9.29, 95% CI: 4.92, 13.66 μg/mg Cr), and PdG (1.01, 95% CI: 0.42, 1.60 μg/mg Cr) were also significantly higher in the luteal phase. In addition, the FSH (0.89, 95% CI: 0.07, 1.71 μg/mg Cr) level in the panel group was significantly higher but E1C (−4.49, 95% CI: −7.90, −1.08 μg/mg Cr) was lower in the early follicular phase; and E1C (−5.16, 95% CI: −9.61, −0.71 μg/mg Cr) level was significantly lower in the periovulatory phase. Conclusions: Our findings add to the evidence that exposure to multiple low-level chemicals is associated with modest changes in reproductive hormone urinary concentrations in healthy premenopausal women. In addition, the FSH (0.89, 95% CI: 0.07, 1.71 μg/mg Cr) level in the panel group was significantly higher but E1C (−4.49, 95% CI: −7.90, −1.08 μg/mg Cr) lower in the early follicular phase; and E1C (−5.16, 95% CI: −9.61, −0.71 μg/mg Cr) level was significantly lower in the periovulatory phase.

Application of a physiologically based pharmacokinetic model for reference dose and reference concentration estimation for acetone

Recent health risk assessments to propose a Reference Dose (RfD) for acetone (Forsyth, 2001; U.S. EPA, 2001) have been based on the results of an oral subchronic study conducted in rats and mice (Dietz et al., 1991; NTP, 1991). These assessments have utilized the traditional concept of establishing the RfD by determining the lowest experimentally determined No-Observed-Adverse-Effect Level (NOAEL) and applying various Uncertainty Factors (UFs) (U.S. EPA, 1988). This article describes a risk assessment for acetone based on the systemic toxicity observed in subchronic and developmental toxicity studies to estimate an RfD and an inhalation reference concentration (RfC) for acetone. Specifically, this approach examined the subchronic study by Dietz et al. (1991), as well as an inhalation developmental toxicity study on acetone (Mast et al., 1988) and several toxicology studies of isopropanol (IPA). This was accomplished by applying a physiologically based pharmacokinetic (PBPK) model developed previously for IPA and its metabolite acetone (Clewell et al., 2001). The incorporation of the PBPK model into the derivation of an RfD and RfC for acetone allowed for a tissue-based approach rather than an external exposure-based approach, making it possible to derive an oral RfD from an inhalation study. In addition, the use of the PBPK model to analyze data from chronic and reproductive/developmental studies conducted with IPA enabled an assessment of the potential for acetone to produce any of the effects observed in the IPA studies. This analysis provided sufficient information to reduce the need for UFs in the adjustment of the NOAEL from the oral subchronic study for the determination of an RfD. Using the PBPK model in the acetone risk assessment supports a composite UF of 60 for the subchronic study, compared to composite factors of 300 to 3000 in the other recent risk assessments. This difference resulted in an RfD of 16 mg/kg/d, compared to the values of 0.3 to 3 that have previously been estimated (Forsyth, 2001; U.S. EPA, 2001). Considering the results from the inhalation developmental study (Mast et al., 1988) resulted in an RfD of 8.7 mg/kg/d. Using this study also fills a data gap for acetone that exists if only the oral database for acetone is considered for RfD derivation. An RfC of 29 ppm was also estimated for acetone using the Mast et al. (1988) study results in combination with the PBPK model. The potential impact of endogenous acetone on a risk assessment for acetone is also discussed.

Application of a physiologically based pharmacokinetic model for isopropanol in the derivation of a reference dose and reference concentration

An interspecies physiologically based pharmacokinetic (PBPK) model describing isopropanol (IPA) and its major metabolite, acetone, was applied to perform route-to-route and cross-species dosimetry to derive reference dose (RfD) and reference concentration (RfC) values for IPA. Adult PBPK models for rats and humans were extended to simulate exposure to IPA during pregnancy and used to estimate internal dose metrics in the mother and fetus during development. Endpoints from chronic, developmental, and reproductive toxicity studies were considered for the derivation of RfDs and RfCs. Due to uncertainties in the mode of action of toxicity for IPA and acetone, the dose metric used for most responses was the total area under the blood concentration curve (AUC) for the combination of IPA and acetone. This combined dose metric provided a more conservative estimate than those based on AUCs for IPA or acetone. Peak blood concentration of IPA was the dose metric for neurobehavioral effects. The recommended RfD and RfC for IPA are 10 mg/kg/day and 40 ppm, respectively, based on decreased fetal body weights. All of the PBPK-derived RfD or RfC values for various endpoints were similar (within a factor of 3), regardless of route of exposure in the animal study.

Calculation of benchmark doses for reproductive and developmental toxicity observed after exposure to isopropanol

Reproductive, including developmental, toxicity risk assessment has typically relied on estimation of toxicity criteria values derived from no-observed-adverse-effect levels (NOAELs). The benchmark dose (BMD) approach has been proposed as an alternative that avoids problems with NOAELs. In this analysis of the reproductive and developmental toxicity observed in a multigeneration study of rats exposed to isopropanol, the BMD approach has been applied to all effects exhibiting significant dose-response relationships. The BMD estimates were very consistent across models and across end points; they were within the range of doses (100 to 500 mg/kg/day) that has been suggested as being the NOAEL. The use of the BMD approach for analysis of isopropanol reproductive toxicity is shown to avoid the experiment-specific argument of whether a particular treatment has induced statistically significant differences, compared to controls, in favor of the estimation of experiment-independent doses corresponding to risk levels of interest. The consistency of the BMD estimates, with values of about 420 mg/kg/day, suggests that, for isopropanol, the available multigeneration study data may provide a suitable basis for considering safe exposure.