Safety assessment of titanium dioxide (E171) as a food additive.

The present opinion deals with an updated safety assessment of the food additive titanium dioxide (E 171) based on new relevant scientific evidence considered by the Panel to be reliable, including data obtained with TiO2 nanoparticles (NPs) and data from an extended one-generation reproductive toxicity (EOGRT) study. Less than 50% of constituent particles by number in E 171 have a minimum external dimension < 100 nm. In addition, the Panel noted that constituent particles < 30 nm amounted to less than 1% of particles by number. The Panel therefore considered that studies with TiO2 NPs < 30 nm were of limited relevance to the safety assessment of E 171. The Panel concluded that although gastrointestinal absorption of TiO2 particles is low, they may accumulate in the body. Studies on general and organ toxicity did not indicate adverse effects with either E 171 up to a dose of 1,000 mg/kg body weight (bw) per day or with TiO2 NPs (> 30 nm) up to the highest dose tested of 100 mg/kg bw per day. No effects on reproductive and developmental toxicity were observed up to a dose of 1,000 mg E 171/kg bw per day, the highest dose tested in the EOGRT study. However, observations of potential immunotoxicity and inflammation with E 171 and potential neurotoxicity with TiO2 NPs, together with the potential induction of aberrant crypt foci with E 171, may indicate adverse effects. With respect to genotoxicity, the Panel concluded that TiO2 particles have the potential to induce DNA strand breaks and chromosomal damage, but not gene mutations. No clear correlation was observed between the physico-chemical properties of TiO2 particles and the outcome of either in vitro or in vivo genotoxicity assays. A concern for genotoxicity of TiO2 particles that may be present in E 171 could therefore not be ruled out. Several modes of action for the genotoxicity may operate in parallel and the relative contributions of different molecular mechanisms elicited by TiO2 particles are not known. There was uncertainty as to whether a threshold mode of action could be assumed. In addition, a cut-off value for TiO2 particle size with respect to genotoxicity could not be identified. No appropriately designed study was available to investigate the potential carcinogenic effects of TiO2 NPs. Based on all the evidence available, a concern for genotoxicity could not be ruled out, and given the many uncertainties, the Panel concluded that E 171 can no longer be considered as safe when used as a food additive.

Blood and exhaled air can be used for biomonitoring of hydrofluorocarbon exposure.

Various hydrofluorocarbons (HFCs) have replaced the ozone-depleting chlorofluorocarbons and hydrochlorofluorocarbons during the last decades. The objective of this study was to examine the usefulness of blood and breath for exposure biomonitoring of HFCs. We compared data on blood and exhaled air from a series of experiments where healthy volunteers were exposed to vapors of four commonly used HFCs; 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, and 1,1,1,3,3-pentafluoropropane. All four HFCs had similar toxicokinetic profiles in blood with a rapid initial increase and an apparent steady-state reached within a few minutes. For all HFCs, the inhalation uptake during exposure was low (less than 6%), most of which was exhaled post-exposure. No metabolism could be detected and only minor amounts were excreted unchanged in urine. The observed time courses in blood and breath were well described by physiologically-based pharmacokinetic (PBPK) modeling. Simulations of 8-h exposures show that the HFC levels in both blood and breath drop rapidly during the first minutes post-exposure, whereafter the decline is considerably slower and mainly reflects washout from fat tissues. We conclude that blood and exhaled air can be used for biological exposure monitoring. Samples should not be taken immediately at the end of shift but rather 20-30 min later.

Experimental exposure to 1,1,1-trifluoroethane (HFC-143a): uptake, disposition and acute effects in male volunteers.

The aim of this study was to determine the toxicokinetics and some effects of 1,1,1-trifluoroethane (HFC-143a) in humans. Nine male volunteers were experimentally exposed to 500ppm HFC-143a for 2h during light physical exercise (50W) in an exposure chamber. Blood, urine and exhaled air were sampled before, during and up to 19h after exposure and analysed for HFC-143a by gas chromatography. These data were described by a physiologically based toxicokinetic (PBTK) model. The electrocardiograms of the volunteers were monitored during exposure. Before, during and after exposure the volunteers rated symptoms related to irritation and CNS-symptoms on a visual analogue scale. Inflammatory markers (C-reactive protein, serum amyloid A protein, D-dimer, fibrinogen) and uric acid were analysed in plasma collected before and 21h after exposure. The exposures were performed after informed consent and ethical approval. The plasma concentration of HFC-143a increased promptly at start of exposure, and decreased in the same manner post-exposure. A stable level of 4.8+/-2.0 microM (mean+/-S.D.) was reached within 30min of exposure. The HFC-143a concentration in plasma and exhaled air decreased fast and in parallel when exposure was stopped. The urinary excretion of HFC-143a after exposure was 0.0007% of the inhaled amount. The half-time in urine, calculated from pooled data, was 53min. The experimental and simulated time courses in blood and exhaled air were in agreement. The simulated relative uptake during the exposure was 1.6+/-0.3%. The fibrinogen level in plasma had increased by 11% 1 day post-exposure. No statistically significant increase was seen for the other inflammatory markers or for uric acid. No effects of exposure were seen either in the electrocardiographic monitorings or as symptom ratings on the visual analogue scale.

Non-positive autoimmune responses against CYP2E1 in refrigeration mechanics exposed to halogenated hydrocarbons.

The aim of the study was to determine if occupational exposure to hydrofluorocarbons (HFC) and hydrochlorofluorocarbons (HCFC) generates autoimmune responses against CYP2E1. HFCs and HCFCs have replaced the chlorofluorocarbons (CFC) in e.g. refrigeration installations and air-conditioning systems. During the substitution period, refrigeration mechanics reported symptoms like asthma, influenza-like reactions, and joint troubles. These symptoms resemble those of chronic inflammatory diseases with an autoimmune component. Since exposure to structurally similar chemicals, e.g. halothane, has previously been associated with autoimmune responses and diseases, autoimmunity among the refrigeration mechanics might hypothetically explain the reported inflammatory symptoms. Serum from 44 Swedish men, occupationally exposed to halogenated hydrocarbons, was screened for antibodies against CYP2E1 with enzyme-linked immunosorbent assay. Thirty of the workers had asthma, joint problems or influenza-like symptoms whereas 14 of them had no such symptoms. They were all selected from a cohort of 280 refrigeration mechanics. Unexposed, healthy, Swedish men (n=35) constituted control group. The study was approved by the Ethics Committee at Karolinska Institutet. No increase in autoantibodies against CYP2E1 was detected among the occupationally exposed workers as compared to the unexposed controls. Further, there was no difference in antibody titer between the exposed workers with symptoms and the exposed, asymtomatic workers or the unexposed controls. The present study does not completely exclude a connection between exposure and effect but makes the relation less likely at these exposure levels.

Toxicokinetics of 1,1,1,2-tetrafluoroethane (HFC-134a) in male volunteers after experimental exposure.

The aim of this study was to determine the uptake and disposition of inhaled 1,1,1,2-tetrafluoroethane (HFC-134a) in humans. Ten male volunteers were exposed to 500 ppm HFC-134a (2 h, 50 W exercise). The HFC-134a levels were monitored in blood, exhaled air and urine up to 19 h post-exposure. The concentration in blood increased rapidly, reaching a plateau of 9.4+/-1.9 microM (mean+/-S.D.) within 30 min, followed by a fast post-exposure decrease. HFC-134a in expired air decreased rapidly as well and in parallel with that in blood. The post-exposure urinary excretion was 0.002% of the inhaled amount, and the half-time was 58 min (pooled data). A physiologically based toxicokinetic (PBTK) model was developed for further analysis. Experimental and simulated time courses in blood and exhaled air agreed well in all 10 subjects. Further, the late decay in blood was consistent with a wash-out of HFC-134a from fat tissues, with a half-time of 114+/-21 min. The simulated relative uptake during exposure was 3.7+/-0.5%. No remarkable findings were observed in the electrocardiographic recordings. Fibrinogen in plasma increased 1 day after exposure, whereas no effects on C-reactive protein, serum amyloid A protein, D-dimer or uric acid were seen. Further studies are needed to investigate the possible inflammatory response.

Inhalation of decomposed chlorodifluoromethane (freon-22) and myocardial infarction.

After exposure to decomposed chlorodifluoromethane (freon-22), a 65-year-old man developed respiratory symptoms such as cough, blood-stained sputum, and increasing dyspnea. Three weeks later, his family doctor diagnosed infectious bronchitis. Another week later he died due to myocardial infarction. The discussion focuses on an inflammatory process caused by the inhalation of decomposed freon and its possible association with myocardial infarction.