B. Toxicity is an Inherent Characteristic of a Substance
1. The dose makes the poison
c. Skin Absorption
a. Metabolic breakdown of substance
C. Which Toxic Substances Are the Most Hazardous? Why?
1. Heavy Metals and Synthetic Organic Compounds
3. Ease of Absorption
Fig. 20.2 At each step or in transportation between steps, wastes, byproducts, or the product itself may enter the environment, causing pollution and creating various risks to human and environmental health.
Fig. 20.3 In halogenated hydrocarbons one or more hydrogen atoms has been replaced by halogen atoms (chlorine, fluorine, bromine, iodine). Such compounds are particularly hazardous to health because they are nonbiodegradable and they tend to bioaccumulate. Shown here are tetrachloroethylene and 1,2-dibromo ethane.
II. Management of Hazardous Wastes
A. Output Control ("command and control" technology: What is done after the pollutant
has been produced?)
1. Deep-well Injection
2. Surface Impoundments
B. Input Control (Pollution Prevention)
2. Elimination of Use
3. Increased Efficiency
4. Closed Loops
Fig. 20.5 The concept is that toxic wastes may be drained into dry, porous strata below ground, where they may reside harmlessly "forever." However, as the figure shows, failures can occur and allow the liquid wastes to contaminate groundwater.
Fig. 20.6 The supposition is that only water leaves the impoundment, by evaporation, while wastes remain and accumulate in the impoundment indefinitely. In reality, this method is subject to failure, and is limited today as a short-term measure.
Fig. 20.7 Precautionary measures to make landfilling safe are listed. Before the 1980s, these measures frequently were not taken. Though they are taken today, potentials for failure remain.
III. Cleaning Up Waste
A. What Do We Do with the Hazardous Waste Sites?
1. Excavate and bury elsewhere
2. Biodegradation on site (bioremediation, phytoremediation)
3. Steam clean soil
4. Groundwater remediation
B. How Well Has Superfund Worked?
1. Evaluating Superfund
Fig. 20.10A Typical subsurface contamination from a leaking fuel tank at a gas station.
Fig. 20.10B After leak repair, vacuum extraction causes gasoline in the soil and the water table to evaporate and removes vapors.
Fig. 20.10C Contaminated groundwater is pumped out, treated, and returned to the ground.
IV. How Do We Reduce Accidents and Accidental Exposure/
A. Underground Storage Tanks UST Legislation
B. Transportation Department of Transportation Regulations
C. Worker Protection OSHA, Worker's Right to Know
D. Community Protection SARA, Title III
E. Chemical Evaluation Before Use TSCA
A. Pollution Prevention and Sustainability
B. Industry Effort
C. Government Efforts
D. Individual Efforts
Fig. 20.12 A cement kiln is a huge, rotating "pipe," typically 15 feet in diameter and 230 feet long, mounted on an incline.
Fig. 20.13 Numbers in place of the word on the placard, or on an additional orange panel, will identify the specific material. Placards alert workers, police, and firefighters to kinds of hazards they face in the case of accidents.
Fig. 20.14 These major laws protect workers, the public, and the environment from hazardous materials.
Fig. 20.15 During communism in the former USSR environmental concerns took a back seat to economic development.