Leaching of phthalate esters from different drinking stuffs and their subsequent biodegradation.

Phthalate esters (PAEs) are mainly used as plasticizers, and their release in the environment during the manufacturing, use, and disposal has caused serious environmental health concerns, since some of them are suspected to be mutagens, hepatotoxic agents, and carcinogens. In the present study, leaching of PAEs from different drinking stuffs (water cooler, mineral water bottles) exposed to sunlight and baby feeders subjected to different heating treatments (boiling, autoclave and oven) was studied. Results showed that a total of 10 PAEs were leached and identified. Among them, dimethyl phthalate, bis(2-methoxyethyl) phthalate, diethyl phthalate, and dibutyl phthalate were the major leached PAEs found in the range 9-112.50 µg L-1. Boiling treatment was found safer for baby feeders as PAE leaching was ~26-54% less as compared to other two treatments. The leached PAEs in water samples were then subjected to biodegradation experiment with Bacillus thuringiensis strain at optimized conditions (time 72 h and 30 °C). Hence, leaching of hazardous PAEs from different water stuffs is alarming and needs immediate attention. Moreover, B. thuringiensis strain was found effective for PAE remediation (75-96% degradation) at neutral pH. Graphical abstract ᅟ.

Removal of compounds used as plasticizers and herbicides from water by means of gamma irradiation.

Gamma radiation has been used to induce the degradation of compounds used as plasticizers and herbicides such as phthalic acid (PA), bisphenol A (BPA), diphenolic acid (DPA), 2,4-dichlorophenoxy-acetic acid (2,4-D), and 4-chloro-2-methylphenoxyacetic acid (MCPA) in aqueous solution, determining the dose constants, removal percentages, and radiation-chemical yields. The reaction rate constants of hydroxyl radical (HO), hydrated electron (eaq(-)) and hydrogen atom (H) with these pollutants were also obtained by means of competition kinetics, using 3-aminopyridine and atrazine as reference compounds. The results indicated that the elimination of these pollutants with gamma radiation mainly follows the oxidative pathway through reaction with HO radicals. The degradation by-products from the five pollutants were determined, detecting that the hydroxylation of the corresponding parent compounds was the main chemical process in the degradation of the pollutants. Moreover, a high decrease in the chemical oxygen demand has been observed for all pollutants. As expected, the degradation by-products generated by the irradiation of PA, BPA and DPA showed a lower toxicity than the parent compounds, however, in the case of 2,4-D and MCPA irradiation, interestingly, their by-products were more toxic than the corresponding original compounds.

A development and biological safety evaluation of novel PVC medical devices with surface structures modified by UV irradiation to suppress plasticizer migration.

This study examines the chemical, physicochemical, and biological properties of PVC sheets treated with UV irradiation on their surfaces to suppress the elution of a plasticizer, di-(2-ethylhexyl) phthalate (DEHP), for developing novel polyvinyl chloride (PVC) medical devices. The PVC sheets irradiated under conditions 1 (52.5 µW/cm(2), 136 J/cm(2)) and 2 (0.45 mW/cm(2), 972 J/cm(2)) exhibited considerable toxicity in cytotoxicity tests and chromosome aberration tests due to the generation of DEHP oxidants, but no toxicity was detected in the PVC sheet irradiated under condition 3 (8.3 mW/cm(2), 134 J/cm(2)). The release of DEHP from the surface irradiated under condition 3 was significantly suppressed, and mono-(2-ethylhexyl) phthalate (MEHP) converted from a portion of DEHP could be easily removed from the surface by washing with methanol. The physicochemical properties of the surface regarding the suppression of DEHP elution remained stable through all sterilizations tested, but MEHP elution was partially recrudesced by the sterilizations except for gamma irradiation. These results indicated that UV irradiation using a strong UV-source over a short time (condition 3) followed by methanol washing and gamma sterilization may be useful for preparing novel PVC products that did not elute plasticizers and do not exhibit toxicity originating from UV irradiation.

Di-(2-ethylhexyl)-phthalate migration from irradiated poly(vinyl chloride) blood bags for graft-vs-host disease prevention.

Irradiation with 20-25 kGy is a process commonly used for sterilizing poly(vinyl chloride) (PVC) medical devices. Moreover, whole blood and blood components undergo additional irradiation with 25-50 Gy to inhibit the proliferative capacity of lymphocytes and reduce the risk of transfusion-associated graft-vs-host disease (GVHD). Di-(2-ethylhexyl)-phthalate (DEHP) plasticized PVC is extensively used for the production of flexible medical devices including blood bags, but since DEHP is not covalently bound to PVC, it tends to migrate and leach out of the medical device, with harmful consequences for the patients. In this study, the effects of different doses of gamma irradiation on DEHP migration from PVC blood bags was investigated using differential scanning calorimetry (DSC) analysis. Our findings indicate that irradiation with 25-100 Gy reduces the ability of DEHP to migrate from the blood bags, and in the case of a primary container a correlation between the doses of gamma ray irradiation was also observed. In particular, a decrease in DEHP leachability was obtained by increasing the dose of gamma ray irradiation.

Surface roughness of denture base and reline materials after disinfection by immersion in chlorhexidine or microwave irradiation.

BACKGROUND: This study evaluated the effect of disinfection by immersion and microwave irradiation on the roughness of one denture base resin (Lucitone-L) and five relining materials, three hard (Tokuyama Rebase II-TR, New Truliner-NT, Ufigel Hard-UH) and two resilient (Trusoft-T, Sofreliner-S). METHODS: Fifty specimens were made and divided into groups: CL2 specimens were brushed with 4% chlorhexidine (1 min), immersed in the same solution (10 min) and immersed in water (3 min); MW2 specimens were immersed in water and microwave irradiated (650W; 6 min); CL2 and MW2 specimens were disinfected twice; CL7 and MW7 specimens were submitted to seven cycles using chlorhexidine or microwave irradiation, respectively; W specimens were not disinfected and remained in water (37°C; 7 days). RESULTS: Results were statistically analysed (p = 0.05) and revealed that, at baseline, the highest mean value was observed for T (p < 0.001). Material NT showed increase in roughness after the first (p = 0.003), second (p = 0.001), seventh (p = 0.000) cycles of microwave disinfection and after 7 days of immersion in water (p = 0.033). CONCLUSIONS: Resilient liner S presented significant increase in roughness after the second cycle of disinfection with chlorhexidine (p = 0.003). Material T exhibited significantly decreased roughness in group W (p = 0.010), while microwaving produced severe alterations on its surface.

Degradation of endocrine disrupting chemicals bisphenol A, ethinyl estradiol, and estradiol during UV photolysis and advanced oxidation processes.

The degradation of three endocrine disrupting chemicals (EDCs), bisphenol A, ethinyl estradiol, and estradiol, was investigated via ultraviolet (UV) radiation photolysis and the UV/hydrogen peroxide advanced oxidation process (AOP). These EDCs have been detected at low levels in wastewaters and surface waters in both the United States and European countries, can cause adverse effects on humans and wildlife via interactions with the endocrine system, and thus must be treated before entering the public drinking water supply. Because many EDCs can only be partially removed with conventional water treatment systems, there is a need to evaluate alternative treatment processes. For each EDC tested, direct UV photolysis quantum yields were derived for use with both monochromatic low-pressure (LP) UV lamps and polychromatic medium-pressure (MP) UV lamps and second-order hydroxyl radical rate constants were developed. These parameters were utilized to successfully model UV treatment of the EDCs in laboratory and natural waters. The polychromatic MP UV radiation source was more effective for direct photolysis degradation as compared to conventional LP UV lamps emitting monochromatic UV 254 nm radiation. However, in all cases the EDCs were more effectively degraded utilizing UV/H2O2 advanced oxidation as compared to direct UV photolysis treatment.

Stabilization of nontoxic PVC formulation for gamma irradiation sterilization, II. Effect of antioxidants.

In order to investigate the fundamental data for the resistance of gamma radiation sterilization of polyvinylchloride (PVC), the formulations of the antioxidants such as commercial Irganox series and inorganic, processing aids, stabilizer aids, trans-stilbene oxide (StO) and so on have been carried out. The control and irradiated PVC samples with 1.5, 2.5 and 4.0 Mrad were characterized by mechanical tester, colorimetry, and extractant in water. Irganox 1010 was more effective than Irganox 1076 for color changes whereas Irganox 1076 was more effective than Irganox 1010 for the change of extractant. It was also observed the significant diminution of color changes for inorganic antioxidants as CaO and ZnO. Oxidized paraffin wax as lubricant, styrene-methylmetacrylate copolymers as processing aids, and nontoxic debenzoylmethane as secondary stabilizer did not show good stabilization for the irradiation. The new proposed radiation stabilizer in this study, StO, showed the significant improvement of gamma radiation resistance for the plasticized PVC. The possible mechanism could be explained that an epoxy functional group stabilizes effectively the processes of dehydrogenation, the formation of hydroperoxides, and the formation of oxygen containing groups, and the synergetic effects of an epoxy compound are more notable for the prevention of radiation oxidation in the presence of an aromatic group.

Stabilization of nontoxic PVC formulation for gamma irradiation sterilization, I. Effect of additives.

In order to investigate the fundamental data for the resistance of gamma radiation sterilization of polyvinylchloride (PVC), the formulations of the additives such as plasticizers of dioctylphthalate, trioctyltrimellitate and polyester, second plasticizers, Ca/Zn nontoxic metallic stabilizers with powder, paste and liquid state, and phosphite stabilizers have been carried out. The control and irradiated PVC samples with 1.5, 2.5 and 4.0 Mrads were characterized by mechanical tester, colorimetry, and extractant in water. The effect of plasticizers observed in the order of dioctylphthalate approximately equal trioctyltrimellitate > polymeric plasticizer. It was observed in the order of Ca/Zn metallic stabilizers of paste > liquid approximately equal powder state for the color change and liquid > paste > powder for the extractant. The mechanism of the discoloration of PVC in our experiment was predominant the formation of polyene by the dehydrochlorination rather than the formation of keton and aldehyde by the oxidation and chain dissociation by the measurement of gel permeation chromatography and mechanical property. The proposed mechanisms of stabilization and discolorization with various additives are also discussed.

Effect of gamma-radiation on migration behaviour of dioctyladipate and acetyltributylcitrate plasticizers from food-grade PVC and PVDC/PVC films into olive oil.

Food-grade PVC and PVDC/PVC films containing 28.3% dioctyladipate (DOA) and 5.0% acetyltributylcitrate (ATBC) plasticizers, respectively, were brought into contact with olive oil and were irradiated with gamma-radiation [60Co] at doses equal to 4 kGy and 9 kGy corresponding to "cold pasteurization". Irradiation was carried out at 8-10 degrees C and samples were subsequently stored at 4-5 degrees C. Contaminated oil samples were analysed for DOA and ATBC at intervals between 7 h and 97 h of contact, using an indirect GC method. Identical nonirradiated (control) samples were also analysed for DOA and ATBC content. Results showed no statistically significant differences in migrated amounts of DOA and ATBC between irradiated and non-irradiated samples. Neither were differences observed between samples irradiated at 4 kGy and 9 kGy. This was supported by identical IR spectra recorded for irradiated and non-irradiated samples and leads to the conclusion that at such intermediate radiation doses (< or = 9 kGy) the migration characteristics of both PVC and PVDC/PVC films are not affected. The amount of DOA that migrated into olive oil was dependent on time, reaching equilibrium after approximately 47 h of contact (302.8 mg/l). The amount of ATBC that migrated into olive oil was non-detectable (< 1 mg/l) for all samples stored at 4-5 degrees C after 97 h. In non-irradiated samples (PVDC/PVC in contact with oil) stored at 20 degrees C, small amounts of migrated ATBC were determined (3.3 and 5.1 mg/l after 29 h 94 h of contact respectively).(ABSTRACT TRUNCATED AT 250 WORDS)