Bisphenol A in the Environment

Transcription

1 Bisphenol A in the Environment Eileen Ekstrom Lecturer, Harvard Extension School, Environmental Management Program Environmental Management 101, Fall 2010

2 From The Graduate: Plastics

3 Plastic products are ubiquitous in modern life One of the most frequently manufactured products in the world. However, health concerns have been raised over the components of certain types of plastics. Polyvinyl chloride (PVC) - phthalates Polycarbonate (PC) Bisphenol A

4 Polycarbonate plastics used to make.

5 Bisphenol A (BPA) Used in the production of polycarbonate plastic and epoxy resins used to line metal cans. In plastic consumer products including: Toys Water pipes Drinking containers Eyeglass Lenses Receipt Thermal Paper Dental Fillings Medical Equipment Consumer Electronics One of the highest volume chemicals produced worldwide 6 billion pounds produced each year

6 Free BPA can be regularly measured in humans Blood: 0.2 to 20 μg/l BPA Urine: Average 1.63 μg/l BPA for adult male, 1.12 μg/l BPA for adult female Fetal Amniotic Fluid (15-18 week): 8.3 μg/l BPA Breast Milk: 0.28 to 0.97 μg/l BPA BPA levels measured in humans are within an order of magnitude of levels used in many animal studies assessing the effects of BPA Vandenberg et al., 2007

7 BPA appears to be an Endocrine Disrupter BPA Estrogen BPA can bind to estrogen receptors, although BPA binds 10,000 to 100,000 fold less strongly than estradiol. Recent finding indicate that BPA can be equally potent as estradiol in a variety of cell tissues, with changes in cell function observed at a dose of 0.23 ng/l Vandenberg et al., 2007

8 Effects of low dose BPA exposure in animals ( μg/kg/day) Change in genital tract Increased prostate weight Signs of early puberty Decline in testicular testosterone Breast cells, prostate cells are more sensitive to cancer USEPA exposure limit: 50 μg/kg/day BPA Environmental Working Group Report,

9 Relatively few epidemiological studies investigating BPA exposure in humans with health effects BPA levels in women s blood have been linked to: obesity endometrial hyperplasia (overgrowth of uterine lining) recurrent miscarriages abnormal karyotypes (abnormality in fetal chromosomes) Polycystic ovarian syndrome Vandenberg et al., 2007

10 What is the source of BPA to humans? A study examining the source of BPA to 257 preschool children found: BPA can be measured in 50% of measured indoor air, hand surfaces, solid food, and liquid food. 99% of exposure to the children was from diet (52-74 ng/kg/day), versus inhalation exposure ( ng/kg/day) Wilson et al., 2007

11 Where is BPA in our food and water coming from? Resin-lined canned food, polycarbonate food and drink containers 4-23 μg per can 6.5 μg/g food after microwaving (estimated) 0.66 to 4.6 μg/l after 24 hrs (room temp., bottle previously heated) Vandenberg et al., 2007; Lee et al., 2008

12 Previous studies have estimated the average human intake of BPA 1 μg BPA/kg body weight/day (Kang et al., 2006) μg BPA/kg body weight/day (European Commission Committee on Food) 4.8 μg BPA/kg body weight/day (Thompson et al., 2003) Let s take it a step further and calculate what an average student s exposure to BPA is from to better understand the sources of BPA to the human diet.

13 Our imaginary student Fred enjoys. A can of Beefaroni for lunch, which he microwaves in his polycarbonate tupperware container. A can of condensed soup for dinner, which he microwaves in his polycarbonate bowl 2 L of water he drinks from his polycarbonate bottle, that he washed in the dishwasher

14 Using the low end of measured BPA release values, let s calculate Fred s BPA exposure for the day Lunch 1 can of Beefaroni (15 oz) microwaved in polycarbonate container 1. From can = 4 μg BPA 2. From microwaving the food 4-23 μg per can 6.5 μg/g food after microwaving (estimated) 6.5 μg BPA g food x

15 Using the low end of measured BPA release values, let s calculate Fred s BPA exposure for the day Lunch 1 can of Beefaroni (15 oz) microwaved in polycarbonate container 1. From can = 4 μg BPA 2. From microwaving the food 4-23 μg per can 6.5 μg/g food after microwaving (estimated) 6.5 μg BPA g food x 28.3 g food oz food x 15 oz food

16 Using the low end of measured BPA release values, let s calculate Fred s BPA exposure for the day Lunch 1 can of Beefaroni (15 oz) microwaved in polycarbonate container 1. From can = 4 μg BPA 2. From microwaving the food 4-23 μg per can 6.5 μg/g food after microwaving (estimated) 6.5 μg BPA g food x 28.3 g food oz food x 15 oz food = 2759 μg BPA 4 μg BPA from can μg from microwaving = 2763 μg BPA from lunch

17 Fred s Dinner 1 can of condensed soup (10.75 oz, 21.5 oz when cooked) microwaved in polycarbonate bowl 1. From can = 4 μg BPA 2. From microwaving the food 4-23 μg per can 6.5 μg/g food after microwaving (estimated) 6.5 μg BPA g food x 28.3 g food oz food x 21.5 oz food = 3955 μg BPA 4 μg BPA from can μg from microwaving = 3959 μg BPA from dinner

18 Fred s Libations 2 L of water stored in his 2 polycarbonate bottles that were previously washed in the dishwasher 0.66 μg BPA L water x 2 L water = 1.32 μg BPA 0.66 to 4.6 μg/l after 24 hrs (room temp., bottle previously heated)

19 Fred s Total Exposure of BPA for the day 2763 μg BPA from lunch μg BPA from dinner 1.32 μg BPA from water 6723 μg BPA for day Let s assume Fred is the average American man s weight (73.48 kg, 162 pounds) 6723 μg BPA day x kg = 91.5 μg/kg/day Higher than the EPA exposure limit of 50 μg/kg/day!

20 If Sally, our typical female student ate the same meal 2763 μg BPA from lunch μg BPA from dinner 1.32 μg BPA from water 6723 μg BPA for day And let s assume Sally is the average woman s weight (61.24 kg, 135 pounds) 6723 μg BPA day x kg = μg/kg/day for Sally vs μg/kg/day for Fred

21 Our calculations seem pretty high compared to previously published exposure estimates μg BPA/kg/day Fred and Sally s exposure vs μg BPA/kg/day Previously published estimates % of our calculated BPA exposure is due to microwaving food in polycarbonate containers Published values on BPA leaching are calculated estimates, not measured rates. Experiments measuring the BPA release while microwaving would help identify if these values are accurate or These calculations indicate that microwaving food in polycarbonate containers is a high source of BPA exposure

22 Through this example, I ve demonstrated the steps in problem solving Determine the scope of the question Research the current data related to the question Make thoughtful assumptions that are clearly stated Write out all the steps while solving the problem to decrease the likelihood of errors At the end, evaluate the assumptions and data used to decide if the answer seems right Though quantitative analysis, one can develop a better understanding of the processes which underlie environmental problems and identify the strengths and weaknesses of our current knowledge.

23 To continue showing how problem-solving can help us better understand our exposure from BPA, I will go through two more problem-solving examples. A cashier s exposure to BPA from BPAlaced thermal paper receipts The transport of BPA leaching from a landfill into a stream next to a school

24 Recent reports have indicated that receipts can contain high levels of BPA Thermal paper often (but not always) contains BPA in the dye that permeates the paper. Upon heating, the dye becomes dark g/kg BPA in thermal receipt paper 11 of 13 thermal receipts tested contained BPA Experiments indicate that a cashier can have 71 μg BPA/day transferred to his or her fingers Biedermann et al., 2010

25 How does the cashier s exposure compare? Cashier (male) = 71 μg BPA/day EPA s Maximum Exposure Limit = 50 μg/kg/day BPA 50 μg BPA kg * day

26 How does the cashier s exposure compare? Cashier (male) = 71 μg BPA/day EPA s Maximum Exposure Limit = 50 μg/kg/day BPA 50 μg BPA kg * day x kg (ave. male weight) =

27 How does the cashier s exposure compare? Cashier (male) = 71 μg BPA/day EPA s Maximum Exposure Limit = 50 μg/kg/day BPA 50 μg BPA kg * day x kg (ave. male weight) = 3674 μg BPA/day 52 times higher than cashier exposure

28 How does the cashier s exposure compare? Cashier (male) = 71 μg BPA/day EPA s Maximum Exposure Limit = 50 μg/kg/day BPA 50 μg BPA kg * day x kg (ave. male weight) = 3674 μg BPA/day 52 times higher than cashier exposure Average Published BPA Exposure = μg/kg/day BPA 0.48 μg BPA kg * day x kg = μg BPA/day

29 How does the cashier s exposure compare? Cashier (male) = 71 μg BPA/day EPA s Maximum Exposure Limit = 50 μg/kg/day BPA 50 μg BPA kg * day x kg (ave. male weight) = 3674 μg BPA/day 52 times higher than cashier exposure Average Published BPA Exposure = μg/kg/day BPA 0.48 μg BPA kg * day x kg = μg BPA/day Dose causing health effects in animals = μg/kg/day BPA μg BPA kg * day x kg = μg BPA/day

30 For another example of BPA fate in the environment Landfill in West Germany = measured 3.61 mg/l BPA in leachate! BPA containing resins and plastics must be degrading in landfill OLD LANDFILL Coors et al., 2003

31 High levels of BPA is leaching into the groundwater from an old, unlined landfill. Groundwater near the landfill feeds into Barry Creek, which passes by an elementary school. What is the concentration of BPA in the stream near the school?

32 Let s assume: (1) the groundwater flow is constant over the time scale relevant for this problem (2) the concentration of BPA in the groundwater is constant over time scale relevant for this problem (3) Barry Creek s flow rate and initial BPA concentration is constant over the time scale relevant for this problem Steady State System Input rate = Output rate

33 Let s also assume BPA is not degraded or accumulated in the groundwater and stream over the time scale of this problem Conservative Pollutant in a Steady-State System stream C s Q s groundwater C g Q g Accum = 0 Reaction =0 C m Q m mixture Q = flow rate C = Concentration of BPA

34 stream C s Q s groundwater C g Q g Accum = 0 Reaction =0 C m Q m mixture Q = flow rate C = Concentration of BPA Because Input = Output, therefore C s Q s + C g Q g = C m Q m

35 Flow rates and concentrations BPA in Barry Creek and groundwater Q s = 10 m 3 /s C s = 0.5 ng/l BPA Q g = 0.1 m 3 /s C g = 3.61 mg/l BPA stream C s Q s groundwater Accum = 0 Reaction =0 C m Q m mixture C g Q g Q = flow rate C = Concentration of BPA

36 Flow rates and concentrations BPA in Barry Creek and groundwater Q s = 10 m 3 /s C s = 0.5 ng/l BPA Q g = 0.1 m 3 /s C g = 3.61 mg/l BPA Units not all the same! Need to convert flow rate to L/s and convert Cs to mg/l stream C s Q s groundwater Accum = 0 Reaction =0 C m Q m mixture C g Q g Q = flow rate C = Concentration of BPA

37 Flow rates and concentrations BPA in Barry Creek and groundwater 1 m 3 = 1000 L Q s = 10 m 3 /s C s = 0.5 ng/l BPA Qs 10 m 3 s x 1000 L = 10,000 L/s 1 m 3 Q g = 0.1 m 3 /s C g = 3.61 mg/l BPA Q g C s 0.1 x 1000 = 100 L/s 0.5 ng L x 1 μg 1000 ng x 1 mg 1000 μg = 5 x 10-7 mg/l stream C s Q s groundwater Accum = 0 Reaction =0 C m Q m mixture C g Q g Q = flow rate C = Concentration of BPA

38 Flow rates and concentrations BPA in Barry Creek and groundwater Q s = 10,000 L/s C s = 5 x 10-7 mg/l BPA Q g = 100 L/s C g = 3.61 mg/l BPA C s Q s + C g Q g = C m Q m (5 x 10-7 mg/l)(10,000 L/s) + (3.61 mg/l)(100 L/s) = C m (10, L/s)

39 Flow rates and concentrations BPA in Barry Creek and groundwater Q s = 10,000 L/s C s = 5 x 10-7 mg/l BPA Q g = 100 L/s C g = 3.61 mg/l BPA C s Q s + C g Q g = C m Q m (5 x 10-7 mg/l)(10,000 L/s) + (3.61 mg/l)(100 L/s) = C m (10, L/s) C m = mg/l = 36 μg/l Even though the flow rate of groundwater from the landfill was so slow, the concentration of BPA near the school is quite high. Student should be advised to not play in the creek.

40 In summary, Bisphenol A is one of the highest volume chemicals produced worldwide found in polycarbonate plastic, resins, and thermal paper appears to act as an endocrine disrupter in biochemical and animal studies some studies in humans link BPA concentration in women to health problems However, there is still some disagreement among review boards on the need for a ban on BPA, while certain states and countries have proceeded with bans on BPA in baby bottles.

41 U.S. NIH Panel (2007) determined that there was "some concern" about BPA's effects on fetal and infant brain development and behavior US National Toxicology Prog. (2008) "some concern for effects on the brain, behavior, and prostate gland in fetuses, infants, and children at current human exposures to BPA," Health Canada (2008) FDA Report (2010) chemical may pose some risk to infants and proposed classifying the chemical as toxic to human health and the environment." Although concluded BPA was safe in 2008, re-reviewed and agreed with NIH, some concern about BPA. EU Food Safety Authority (2006) "considerable reservations" about the biological significance and robustness of the low-dose exposure studies on rodents

42 U.S. NIH Panel (2007) determined that there was "some concern" about BPA's effects on fetal and infant brain development and behavior US National Toxicology Prog. (2008) "some concern for effects on the brain, behavior, and prostate gland in fetuses, infants, and children at current human exposures to BPA," Health Canada (2008) FDA Report (2010) chemical may pose some risk to infants and proposed classifying the chemical as toxic to human health and the environment." Although concluded BPA was safe in 2008, re-reviewed and agreed with NIH, some concern about BPA. EU Food Safety Authority (2006) "considerable reservations" about the biological significance and robustness of the low-dose exposure studies on rodents

43 BPA Bans Countries/U.S. States that ban BPA in children s feeding products Canada Denmark Connecticut, Minnesota, Vermont, New York, Washington, Wisconsin, Maryland EU (2011) After 2008 ban by Canada, Walmart and Toy R Us announced that they will quickly phase out BPA-containing baby bottles In 2008, Nalgene also announced it will stop using the chemical in its products In 2009 after the Connecticut ban, 6 major baby bottle manufacturers announce they will stop producing BPA-containing bottles for U.S.

44 Most recently, On Nov. 30, 2010, the U.S. Senate passed the FDA Food Safety Modernization Act However, an initiative to restrict BPA in food containers was removed from the bill prior to passage