NATS 1510 Lecture 8

NATS 1510 Lecture 8 – Science in Nature: Chlorinated Compounds
Human beings, public health and environmental issues
Chlorinated compounds, “lack the telltale characteristics - smoke, smog, taste, and
odor” lack of scientific and public attention
Health consequences of exposure delayed (e.g. cancer)
Chlorinated compounds used as degreasers and in CFC refrigerants
Degreasers common, machinery, lubrication, refrigerants common, food
transportation and preservation
Delayed environmental action on chlorinated solvents in part due to lack of
scientific consensus on environmental consequences:
o contaminant pathways
o the physical-chemical processes occurring along their length
o accepted modes of measurement
o biomedical effects of the contaminants on public health.
By 1981 US groundwater contamination of aquifiers a national problem
Why did it take that long for the problem to be found?
o Chlorinated compounds a shop floor problem, workplace issue
o Hydrologists unable to test for contaminants in groundwater
o No scientific model of contaminant migration
o These factors interacted to reduce inquiry into the science of groundwater
Other chlorinated compounds, pesticides like DDT
CFC’s linked to ozone depletion, scientific model present
Ground water contamination scientific model in 1980’s, delayed remedial action
- Materials that are to be “painted, machined, welded, heat-treated, assembled,
electroplated, or packaged” have to first be degreased
- Vapor degreasing process, solvent is vaporized and piece immersed in vapor
- Growth of automobile industry in 1930’s, growth in degreasers, WWII demand
- Emissions from organic solvents subject of environmental legislation in 1960’s,
different varieties of chlorinated compounds prohibited
- Discovery of “ozone hole” in Antarctic, strict regulation of CFCs, varieties of
degreaser solvent
- Chlorinated compounds flagged as groundwater contaminants 20 years before
CFC’s, some degreaser compounds illegal
- 1960’s: detection of chlorinated compounds in groundwater, 1980’s: scientific
model for migrating compounds
- chlorinated compounds identified in groundwater contamination as early as 1945
in the US, and degreaser compounds as early as 1949 in the UK
- Chlorinated pesticide pollution, recognition of a national problem by 1980’s
- Groundwater contamination by chlorinated solvents not predicted, no suitable
instruments to test for it
- Interest in groundwater contamination from other chlorinated solvents (pesticides)
motivated developments that later led to the discovery of degreasing solvents
1970’s laws restricting allowable amount of chlorinated compounds in drinking
water, technical improvements in detection technology in mid-1970’s
The Safe Drinking Water Act - widespread testing for chlorinated compounds like
pesticides, found degreasing solvents
Computer model for spilled solvent migration in 1980’s
1970’s insurance companies advising industry to dump chlorinated compounds on
dry ground and allow vapors to disperse
1980’s environmental tests finding ‘plumes’ of hydrocarbons trapped under the
soil and migrating into water supplies
Computer models of trapped and migrating solvents developed in 1980’s in
“migration, trapping, and dissolution” of chlorinated compounds outside scope of
hydrology until 1980’s
- New chemicals, government and industry, harm
- Regulatory action waits until scientific consensus has emerged
- Funding lacking as problem not recognized