New Term Paper Due Dates

November 18 – final version of paper for peer editing.

December 2 – return edited papers to classmates.

December 9 – Final edited paper due.

Persistent Organics in the Environment

Some common persistent organics:

DDTPCBs

DioxinsPBDEMTBE

Persistent Organics in the Environment

Why are we concerned?

1.Bioaccumulation2.Stability3.Toxicity

Persistent Organics in the Environment

1. Bioaccumulation

Due to their low solubility, persistent organics tend to partition to soils and animal fats.

This partitioning can be modeled to within about a factor of 10 using octanol (C8H17OH).

Persistent Organics in the Environment

1. Bioaccumulation

water

octanol

SSKOW

Persistent Organics in the Environment

1. Bioaccumulation

This is usually reported as the logKow because the values for molecules of interest can be quite large.

Online database:http://logkow.cisti.nrc.ca/logkow/index.jsp

water

octanol

SSKOW

Persistent Organics in the Environment

1. Bioaccumulation

From: www.absc.usgs.gov

Do to the stability and partitioning of organics in fatty tissue, the concentration of organics may magnify many orders of magnitude through several trophic levels.

Persistent Organics in the Environment

2. Stability:

Low volatility – no gas phase sink.

Low solubility – not very mobile.

Usually consist of chlorine or bromine bonded to an aromatic ring – not very reactive.

Long lifetime – can be transported long distances over time.

Persistent Organics in the Environment

2. Stability water

octanol

SSKOW

From: Thomann, Environmental Health Perspectives Volume 103,Supplement 5, June 1995

Persistent Organics in the Environment

3. Toxicity

• exposure• acute versus chronic toxicity• mode of toxicity

• mutagen• carcinogen• teratogen

• dose-response relationship

Persistent Organics in the Environment

3. Toxicity

• Exposure depends on Kow.

water

octanol

SSKOW

From: Thomann, Environmental Health Perspectives Volume 103,Supplement 5, June 1995

Persistent Organics in the Environment

3. Toxicity

From: www.rstp.uwaterloo.ca

Dose is usually expressed as a mass of chemical per mass of organism.

Response is usually expressed as the % of the population that has a specific response (or dies) after exposure to the corresponding dose.

Persistent Organics in the Environment

3. Toxicity• Major health concerns:

• Chronic• hormone disruption• cancer development• birth defects

• Acute• all of the above• allergic reaction• respiratory issues

para-dichlorodiphenyltrichloroethane

(DDT)•Used to control typhus and malaria during WWII.

•Used as an agricultural pesticide since WWII.

•1.8 million metric tonnes released to the environment worldwide.

•Banned in the US in 1972 and subsequently worldwide.

•Still used today in the tropics to control mosquitoes that carry malaria.

DDTlog Kow = 6.2

para-dichlorodiphenyltrichloroethane

(DDT)

•DDE (dichlorodiphenyldichloroethane) is a major derivative of DDT and is responsible for much of both the effectiveness of DDT and its harmfulness.

DDT DDE

para-dichlorodiphenyltrichloroethane

(DDT)

DDT

•Kills bugs by interfering with their neurological activity.

•Causes thinning of shells in predatory birds.

•Low acute toxicity for humans (LD 50 ≈ 113mg/kg)

From: www.geo.arizona.edu

para-dichlorodiphenyltrichloroethane

(DDT)log Kow = 6.91

para-dichlorodiphenyltrichloroethane

(DDT)

From: National Resources Defense Council

Polychlorinated biphenyl (PCBs)

209 individual compounds, about 130 were commonly used.

Polychlorinated biphenyl (PCB)Industrial production began in 1929

•Approximately 1.5 million metric tonnes have been produced globally.

•Production peaked in the 1960s.

•Mostly banned in the 1970s for ‘open’ uses.

•No new production today, however, some PCBs are still in use.

•insulating fluid for transformers and capacitors•plasticizer•fire retardant

Polychlorinated biphenyl (PCB)

Properties:•Low water solubility•High organic solubility•Generally low vapor pressures•Chemically stable•log Kow = 5.2 (4,4’-dichlorobiphenol)

Acute toxicity for humans:•grams/kg

For fish:•µg/kg

Polychlorinated biphenyl (PCB)Removal from the environment involves:•dispersion – slow due to bioaccumulation•chemical breakdown – slow due to stability•removal of contaminated soils or sediments – must then store the contaminated material•incineration – potential to create other hazardous materials – furans and dioxins

•microbial – conversion to Cl2 and biphenyl

Polychlorinated biphenyl (PCB)Hudson River PCBs

General Electric dumped up to 1.3 million lbs of PCB into the Hudson river between 1947 and 1977.

Dredging to remove contaminated sediments began earlier this year (2009).

From: www.riverkeeper.org

Polychlorinated biphenyl (PCB)

From: New York State Dept of Environmental Conservation

From: National Resources Defense Council

Polychlorinated biphenyl (PCB)USEPA suggests a maximum safe level for consumption is 3 ppm in dairy, meat, and seafood.

DioxinSources:

•Natural – is created anytime organic material is burned in the presence of chlorine.

•Industrial – is created anytime organic material is burned in the presence of chlorine.

•incineration•pulp and paper bleaching

•Mostly a by-product of other processes, however has been used directly.

•defoliant – Agent Orange•poison

Dioxinchloracne

Viktor Yushchenko, president of Ukraine, was allegedly poisoned with dioxin and had dioxin levels thousands of times greater than found in average blood.

Dioxin

Toxicity:

LD50 = 100s of µg/kg for the most toxic form.

2,3,7,8-Tetrachlorodibenzodioxin (TCDD)

Dioxin

From: Natural Resources Defense Council

Dioxin

From: Natural Resources Defense Council

log Kow = 6.8(TCDD)

Polybrominated diphenyl ethers(PBDE)

Flame retardant

•Integrated into many consumer products including plastics and fabrics.

•Still produced in the US, recently banned in California, Washington, and Maine. Banned in the European Union.

•LD50 is grams/kg•log Kow = 5.8

Polybrominated diphenyl ethers(PBDE)

From: Natural Resources Defense Council

Polybrominated diphenyl ethers(PBDE)

From: Natural Resources Defense Council

Methyl tert-butyl ether (MTBE)

Fuel additive

•Increases octane number.• Reduces engine knocking – replaced lead• Reduces VOC emissions from gasoline.

•LD50 = 4g/kg (comparable to pure ethanol)•log Kow = 0.94

Methyl tert-butyl ether (MTBE)

Seeps into groundwater from underground fuel storage tanks.

-gives water an unpleasant taste at 5µg/L

Has been measured in well water around Santa Monica and Lake Tahoe

-California now has regulations for MTBE (5µg/L)

Next Week’s Exam• The exam is on Wednesday, November 4

during the first 50 minutes of regular class time.

• You are allowed to use a calculator (no PDAs or cell phone calculators).– You may not use your calculator to look at

pre-recorded notes – this is considered cheating.

– Don’t forget your calculator, there will be no extras to hand out.

Next Week’s Exam• No aids in addition to a calculator are

allowed.• Do everything possible to avoid even the

suggestion of cheating:– no hats, sunglasses, wandering eyes, etc.

• Partial credit can be given only if your work is well organized and easily readable.

• All calculations need to be worked out on the exam to receive credit, even if you have the correct answer.

Next Week’s Exam

• The form of the exam:– Multiple choice:

• 20-30%– Short answer

• 30-40%– Worked out calculations

• 30-40%

• This exam is worth 22% of your grade.

Next Week’s Exam

• Priority of material on the exam:– Topics covered in lecture– Topics covered by the assigned reading

• You are responsible for material in the readings, even if it was not explicitly covered in lecture.

• Preparing for the exam:– Do the suggested problems– Study the lecture notes– Study text