• Return HW and Group Assignments
• Turn in Toxicology HW (last homework)
• Today’s Group Assignment on Alternative Fuel and
Toxicology
• Final Exam
– Scheduled for Wednesday, 5/20 5:15 to 7:15 PM
– Not cumulative and same percent toward overall grade as exam 1 and 2
– will give you 2 hours

• Today’s Lecture
– Review of Last Week’s Topics
– Additional Toxicology (Redistribution and Fate of Substances)
– Review for Final Exam
– Skipping Soil Chemistry Section (due to failing voice + limited time)
– Will have two sets of teaching evaluations (one for me and one for Justin)
– Any comments on the group activities would be appreciated

Biofuels
– Reduction in CO
2 production with fuels from renewable resources
– Oxygenated fuels are also cleaner burning
– Fuels as waste products (used cooking oil and cellulose) reduce overall resource use
– Problems from using high % renewables in fuel
– Land requirements are high if % of fuels from biofuel sources is significant
– Competition with food

Biofuels
• food competitive (starch and sugar)
• cellulose (large % of ag waste)
• feedstock affects viability and competition
•
• storage/use issues (decomposition and precipitation) higher NO x emissions

Toxicology
- Review of Exposure Section
•
• Dermal – contact with liquids, gases or solids
• Inhalation – typically major problem with gases and aerosols
• Oral – inadvertent ingestion or contamination of food or drink

Toxicology
- Review of Exposure Section
•
– Form of Toxic Substances Matter
• Phase of molecule
• Polarity of molecule
• pK a for acids or bases
– Exposure Time

Toxicology
- Review of Dose-Response Section
•
•
• LD
50 occurs in middle of distribution, but distribution can depend on factors
• Steepness of response curve affects range of concentrations inducing an effect
• Exposure must be set low enough not to generate effects at low concentration end of response curve

Toxicology
• Movement to target organs/tissue (e.g. Hg to nerve tissue)
• Storage Tissue/Organs
– fats (for compounds with large K ow s)
– bones (for certain inorganic compounds)
• Organs with High Concentrations:
– Liver + Kidneys
– Normal because these organs used for chemical transformation (liver) or excretion (kidney)

Toxicology
Toxic compounds in the body can be: 1) excreted or 2) transformed
Water soluble compounds tend to be excreted more quickly, while lipid soluble compounds can have long lifetimes (months)
A common transformation is enzymatic oxidation in the liver (particularly for lipid soluble compounds)
Oxidation can lead to decreases or increases in toxicity, but usually leads to faster excretion due to increase in polarity

Toxicology
• Some Common
Transformations:
– Hydroxylation
– Dealkylation (alkyl groups attached to N,
O, or S)
– Oxidation
– Epoxidation
– Glucuronic Acid
Addition
RNHCH
3
RCH
3
RCH=CH
2
O
H
H
OH
H O
H
OH
H
O H
OH
OH
+
H O
RCH
2
OH
O
RCH--CH
2
RNH
2
+ CH
2
O
O
H
H
OH
H O
H
OH
O H
H
OH
O
OH
RCH
2
O
RC(OH)HCH
2
OH

Toxicology
• Hypothetical Example
– Moderately polar compound (compound A) is slowly eliminated and transformed to product (compound B)
– Compound B is eliminated faster than compound A
(Only reaches low concentration)
Conc.
A – elimination only
A – both losses
Compound B
A – transformation only
Time

Toxicology
• Polar/Water soluble compounds are often eliminated through urination
• Volatile compounds can be eliminated by exhalation
• Less polar compounds can be removed from liver through bile (goes back to GI tract)
• Other routes
– GI tract
– Sweat

Toxicology
• Exposure is often difficult to assess accurately
– Example: wood smoke in winter
– can measure outdoor concentrations (but it is variable under inversion conditions)
– many people are inside (indoor concentrations are lower)
– people exercising under high pollution conditions (early evening running) are likely to be exposed to much higher concentrations than to others
• An alternative approach is to directly measure concentrations of toxin or metabolites in urine
• Factors affecting exposure then can be studied by comparing environmental concentrations with detected amounts

Break for Group Activity

Toxicity
• Acute Effects
– exposure period is typically short but intense
– effects occur soon after exposure
– effects may be reversible or irreversible
• Chronic Effects
– exposure period is typically over a period of time
– effects generally take time to develop (e.g. cancer)
– may occur from build up of product (e.g. calcium oxalate from ingestion of ethylene glycol)
– may result from body’s reaction to toxin (e.g. build up of scar tissue)
– may occur for low probability effects (mutation of
DNA)
– determining relationship is more difficult

Toxicity
•
– Compounds that affect normal development of fetuses
•
– Cause changes to DNA sequences
•
– Compounds that can lead to the development of cancer

Toxicity
• Effects of Carcinogens
– Most carcinogens (or their metabolites) can react with and alter DNA
– Carcinogens may react with base pairs (e.g. aromatic compounds) or with sugar or phosphate parts
– Many changes to DNA sequence have little effect
(may kill cell or have minor effects)
– Changes to DNA can affect normal mechanisms to restrict cell growth
– Proliferation of deformed cells is what leads to problems with cancer

Toxicity
•
– Epidemiological Studies (comparison of environmental exposure with effects on population)
– Animal Tests (e.g. feeding compounds to rats or mice)
– Ames Test (bacterial screening test for mutagens)

Toxicity
1.
The LD
50 for paraquat is about 100 mg/kg. Estimate the amount of paraquat that would need to be ingested by a “typical” 50 kg woman to just die from it.
2.
Why might it be prudent to limit exposures of toxic compounds to several orders of magnitude under the LD
50
?
3.
What are possible metabolic products of CH
2
=CHCH
2
OCH
3
?
4.
Regulations often limit toxic substances through a) absolute concentration limits and b) time averaged concentration limits.
Why would two separate limits be useful? What are the two limits protecting against?

Exam 3
I.
Climate Change
• Be able to balance solar light in with infrared light out (with and without albedo considerations)*
• Blackbody emissions (total flux as a function of T* and wavelength dependence)
• Understand main absorbing species in the atmosphere for solar radiation and infrared radiation
• Understand effect of increasing greenhouse gases on radiation balance
• Requirements for a molecule to be able to absorb in
IR and basis for relative effectiveness of different gases
* Need to be able to perform calculations

Exam 3
I.
Climate Change – cont.
• Main causes for increases in main greenhouse gases
(CO
2
, CH
4
, N
2
O, CFCs)
• Differences between long-lived greenhouse gases
(those above) and other climate affecting compounds
(ozone and aerosols)
• Direct and Indirect aerosol effects on climate
• Concepts of positive and negative feedbacks on climate
• What sensitivity refers to

Exam 3
II. Fuels and Energy
• Major uses of energy
• Why requirements for different fuels depend on use
• Three main fossil fuel sources
• The significance of energy efficiency (heat per mol of
CO
2 generated)
• The basic strategy in carbon capture
III. Green Chemistry
• Main Goals of Green Chemistry (see slide 8)
• Should know several of the 12 principles

Exam 3
III. Green Chemistry – cont.
• Be able to judge how specific principles apply to alternative syntheses and products (e.g. hazard assessment if MSDS type information is given)
• Be able to calculate atom economy*
• Some of the major types of changes to make a process or product “greener” (product, solvent, feedstock, energy requirements)
IV. Biofuels
• Rationale for Use and Limitations
• Feedstock sources
• Secondary advantages of fuels

Exam 3
V.Toxicology
• Concept of Exposure
• Routes of Entry + issues with these
• How form of compound affects toxicity
• Meaning of LD and Dose – Response Plots (plus be able to read)
• Two major routes of toxic compound transformation and elimation
• Common transformation reactions and their effects on toxic compounds
• Differences between acute and chronic effects
• Definition of carcinogens, teratogens, and mutagens
• Methods of determining carcinogens