Xu-Liang Cao

Levels of Bisphenol A in Canned Soft Drink Products in Canadian Markets

The method developed previously for the determination of bisphenol A (BPA) in liquid infant formula was adapted and validated for determination of BPA in soft drink products. This method was based on solid phase extraction and derivatization with acetic anhydride followed by gas chromatography-mass spectrometry in selected-ion monitoring mode. The average method detection limit was 0.045 microg/L for a 10 mL sample. The average extraction recoveries were 101 and 99.9% obtained with seven different soft drink products spiked with BPA at 0.5 and 2.5 microg/L, respectively. Good repeatability of the method was observed with replicate analyses of seven different soft drinks; relative standard deviations ranged from 1.3 to 6.6%. This method was used to analyze samples of 72 canned soft drink products for BPA. Except for three products from which BPA-d16 could not be recovered at all due to interference of product compositions (e.g., quinine hydrochloride in tonic water), BPA was detected in samples of all the other products at levels ranging from 0.032 to 4.5 microg/L. About 75% of the products had BPA levels of <0.5 microg/L, and 85% of the products had BPA levels of <1 microg/L. Exposure to BPA through consumption of canned soft drink products is low; dietary intake of BPA was estimated at 0.027 microg/kg of body weight/day on the basis of the consumption of one canned soft drink with the highest BPA level (4.5 microg/L) for an adult with a 60 kg body weight, well below the provisional tolerable daily intake of 25 microg/kg of body weight/day established by Health Canada.

Concentrations of bisphenol A in the composite food samples from the 2008 Canadian total diet study in Quebec City and dietary intake estimates

A total of 154 food composite samples from the 2008 total diet study in Quebec City were analysed for bisphenol A (BPA), and BPA was detected in less than half (36%, or 55 samples) of the samples tested. High concentrations of BPA were found mostly in the composite samples containing canned foods, with the highest BPA level being observed in canned fish (106 ng g−1), followed by canned corn (83.7 ng g−1), canned soups (22.2–44.4 ng g−1), canned baked beans (23.5 ng g−1), canned peas (16.8 ng g−1), canned evaporated milk (15.3 ng g−1), and canned luncheon meats (10.5 ng g−1). BPA levels in baby food composite samples were low, with 2.75 ng g−1 in canned liquid infant formula, and 0.84–2.46 ng g−1 in jarred baby foods. BPA was also detected in some foods that are not canned or in jars, such as yeast (8.52 ng g−1), baking powder (0.64 ng g−1), some cheeses (0.68–2.24 ng g−1), breads and some cereals (0.40–1.73 ng g−1), and fast foods (1.1–10.9 ng g−1). Dietary intakes of BPA were low for all age–sex groups, with 0.17–0.33 µg kg−1 body weight day−1 for infants, 0.082–0.23 µg kg−1 body weight day−1 for children aged from 1 to 19 years, and 0.052–0.081 µg kg−1 body weight day−1 for adults, well below the established regulatory limits. BPA intakes from 19 of the 55 samples account for more than 95% of the total dietary intakes, and most of the 19 samples were either canned or in jars. Intakes of BPA from non-canned foods are low.

Cohort Profile: The Maternal-Infant Research on Environmental Chemicals Research Platform

BACKGROUND The Maternal-Infant Research on Environmental Chemicals (MIREC) Study was established to obtain Canadian biomonitoring data for pregnant women and their infants, and to examine potential adverse health effects of prenatal exposure to priority environmental chemicals on pregnancy and infant health. METHODS Women were recruited during the first trimester from 10 sites across Canada and were followed through delivery. Questionnaires were administered during pregnancy and post-delivery to collect information on demographics, occupation, life style, medical history, environmental exposures and diet. Information on the pregnancy and the infant was abstracted from medical charts. Maternal blood, urine, hair and breast milk, as well as cord blood and infant meconium, were collected and analysed for an extensive list of environmental biomarkers and nutrients. Additional biospecimens were stored in the studys Biobank. The MIREC Research Platform encompasses the main cohort study, the Biobank and follow-up studies. RESULTS Of the 8716 women approached at early prenatal clinics, 5108 were eligible and 2001 agreed to participate (39%). MIREC participants tended to smoke less (5.9% vs. 10.5%), be older (mean 32.2 vs. 29.4 years) and have a higher education (62.3% vs. 35.1% with a university degree) than women giving birth in Canada. CONCLUSIONS The MIREC Study, while smaller in number of participants than several of the international cohort studies, has one of the most comprehensive datasets on prenatal exposure to multiple environmental chemicals. The biomonitoring data and biological specimen bank will make this research platform a significant resource for examining potential adverse health effects of prenatal exposure to environmental chemicals.

Migration of Bisphenol A from Polycarbonate Baby and Water Bottles into Water under Severe Conditions

The isotope dilution headspace solid-phase microextraction and gas chromatography-mass spectrometry method for bisphenol A (BPA) developed previously was used successfully in a BPA migration study at 70 degrees C of polycarbonate baby and reusable water bottles recently sold in Canada by using the whole bottles instead of pieces cut from the bottles. Migration of BPA from the PC bottles heated at 70 degrees C was found to increase over the time in the quadratic equations. Migration levels of BPA in water varied from 228 to 521 microg L (-1) or from 0.26 to 0.90 microg cm (-2) after being heated at 70 degrees C for 6 days. The average migration rates of BPA from the PC bottles into water at 70 degrees C ranged from 1.84 to 4.83 ng cm (-2) h (-1).

Bisphenol A in human placental and fetal liver tissues collected from Greater Montreal area (Quebec) during 1998–2008

In this study, the presence of bisphenol A (BPA) in human placental and fetal liver samples collected from 1998 to 2008 was investigated to provide a more detailed analysis of the transfer of BPA across the placenta and fetal exposure to BPA. The average concentrations in placental samples were 12.6 ng g(-1) for free BPA, 17.2 ng g(-1) for BPA-glu, and 30.2 ng g(-1) for total BPA. The highest concentrations in placental samples were 165 ng g(-1) for free BPA, 178 ng g(-1) for BPA-glu, and 280 ng g(-1) for total BPA. Samples with higher levels of BPA-glu had higher levels of free BPA in general. Fetal age was observed to have a significant effect on BPA-glu levels in placental samples, but not on free or total BPA. The percentages of free BPA relative to total BPA for the placental samples varied considerably from 4.2% to 100%, suggesting that the ability of maternal liver and/or the placenta to conjugate BPA is highly variable during early to mid-gestation. The average concentrations in fetal liver samples were 9.02 ng g(-1) for free BPA, 19.1 ng g(-1) for BPA-glu, and 25.8 ng g(-1) for total BPA. The highest concentrations in fetal liver samples were 37.7 ng g(-1) for free BPA, 93.9 ng g(-1) for BPA-glu, and 123 ng g(-1) for total BPA. The percentages of free BPA level relative to total BPA for all fetal liver samples varied from 12.4% to 99.1%, indicating extensive variability in the ability of the human feto-placental unit to glucuronidate BPA.

Canadian Total Diet Study in 1998: Pesticide levels in foods from Whitehorse, Yukon, Canada, and corresponding dietary intake estimates

The Canadian Total Diet Study is a national survey to determine the level of chemical contaminants in the Canadian food supply. Food samples were collected from Whitehorse, Yukon, supermarkets as part of the study in 1998. Whitehorse was chosen as a sampling centre, despite its small population (n = 19 000), to determine if residue levels were different in foods available in northern communities relative to levels observed in previous studies in the more populated south. Foods were prepared as for consumption before pesticide residue analysis. Residue levels observed in most foods were similar to levels observed in samples from previous surveys from southern Canadian cities. Malathion and DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene), a transformation product of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl(ethane), were the two most frequently detected compounds (26.4 and 25.8%, respectively). The majority of pesticides, however, had a detection frequency of <5%. In general, pesticides in food composites were well below maximum residue limits established in the Canadian Food and Drug Regulations. Chlorpropham and captan had the highest dietary intakes (2.16 and 1.94 µg (kg body weight-day)−1, respectively), based on the results from Whitehorse. No dietary intakes above the acceptable daily intakes, however, were observed for any of the 39 pesticides investigated in any age–sex category, where an acceptable daily intake has been proposed.

Bisphenol A activates the Nrf1/2-antioxidant response element pathway in HEK 293 cells.

Bisphenol A (BPA) is used in the production of polycarbonate plastics and epoxy resins for baby bottles, liners of canned food, and many other consumer products. Previously, BPA has been shown to reduce the activity of several antioxidant enzymes, which may contribute to oxidative stress. However, the underlying mechanism of the BPA-mediated effect upon antioxidant enzyme activity is unknown. Antioxidant and phase II metabolizing enzymes protect cells from oxidative stress and are transcriptionally activated by Nrf1 and Nrf2 factors through their cis-regulatory antioxidant response elements (AREs). In this work, we have assessed the effect of BPA on the Nrf1/2-ARE pathway in cultured human embryonic kidney (HEK) 293 cells. Surprisingly, glutathione and reactive oxygen species (ROS) assays revealed that BPA application created a more reduced intracellular environment in cultured HEK 293 cells. Furthermore, BPA increased the transactivation activity of ectopic Nrf1 and Nrf2 and increased the expression of ARE-target genes ho-1 and nqo1 at high (100-200 μM) BPA concentrations only. Our study suggests that BPA activates the Nrf1/2-ARE pathway at high (>10 μM) micromolar concentrations.

Determination of free and total bisphenol A in human milk samples from Canadian women using a sensitive and selective GC-MS method

A sensitive and selective GC-MS method was developed and used to analyse human milk samples for both free and total bisphenol A (BPA). Total BPA was detected in 72 of the 278 human milk samples (25.9%) at concentrations from < 0.036 to 2.5 ng g–1 with a geometric mean (GM) of 0.13 ng g–1 and median of 0.11 ng g–1, while free BPA was detected in fewer samples, 46 of the 278 samples (16.5%) at concentrations ranging from < 0.036 to 2.3 ng g–1 with a GM of 0.11 ng g–1 and median of 0.10 ng g–1. Ratios of [free BPA]/[total BPA] for the positive samples ranged from 7.9% to 100% with a GM of 57.2% and median of 70.3%. Concentrations of free and total BPA in most samples were low with 0.39 and 0.65 ng g–1 at the 95th percentile for free and total BPA, respectively, and they are also lower than those reported in other countries. Based on the low frequency of detection of free BPA in human milk samples, in general, dietary exposure to BPA for Canadian breast-fed infants is expected to be somewhat lower compared with exposure among formula-fed infants.

Background bisphenol A in experimental materials and its implication to low-dose in vitro study.

In vitro low-dose studies are important to understand the mechanisms of bisphenol A (BPA) action. BPA doses used in current in vitro studies varied considerably, and doses as low as 10(-15)M have been reported. The actual doses of BPA used in the in vitro low-dose studies were rarely checked analytically, and the background BPA levels in experimental materials, which will determine the lowest BPA dose to be used, should be investigated or considered. In this study, the background BPA levels in various materials typically used in in vitro low-dose studies for BPA were investigated. Background BPA levels from the use of disposable pipettes and pipette tips were low (<0.20 ng mL(-1) or 0.88 nM). BPA was also detected in several commercial buffer solutions at levels close to the method limit of quantification (LOQ) (0.02 ng mL(-1); 0.088 nM). However, BPA was detected in all cell culture media obtained from various sources at levels ranging from 0.080 to 4.26 ng mL(-1) (or 0.35 to 19 nM) with an average of 0.83 ng mL(-1) (3.5 nM). We suggest that culture media used for low-dose BPA studies should be analysed for background BPA levels prior to use, and the medium with the lowest BPA levels should be used.

Improved method for the determination of benzene in soft drinks at sub-ppb levels

An automated, simple, and reproducible method based on isotope dilution headspace gas chromatography/mass spectrometry developed previously for the determination of benzene in soft drinks was further improved by adding sodium sulfate to samples, lowering the gas chromatography oven starting temperature to narrow benzene peak width, and increasing sample injection volume. This improved method had a lower detection limit (0.016 µg l−1) and good repeatability, and was used in a follow-up survey to assess benzene levels in 139 samples of soft drink products. Benzene was detected in 67% of the 139 products tested. Compared with the previous survey, the average benzene concentrations in most products from this survey were lower, and only a few products had benzene at elevated levels.