1. Historically, in the late 1800s and early 1900s, toxic gases such as ammonia, methyl chloride, and sulphur dioxide were used as refrigerants. Due to the ill effects of these chemicals, a less toxic replacement was required. Collaborative efforts between Frigidaire, General Motors, and DuPont brought CFCs into the picture. In 1928, Thomas Midgley, Jr. of General Motors was responsible for the creation of CFCs.
2. All replacement compounds for CFCs are evaluated for their ozone depletion potential (ODP).
1. Persistent organic pollutants (POPs) are organic compounds that resist environmental breakdown via biological, chemical, and photolythic processes, some taking as long as a century to degrade.
2.POPs therefore can be found globally, even in areas such as the Arctic and Antarctica, far from their source. Human exposures in certain Arctic areas are among the highest worldwide.
1. Artificial fertilizers are usually liquid or powdered chemicals (or occasionally gas), containing a mix of nitrogen, phosphorus or potassium. They also have traces of sulfur, magnesium and calcium.
2. Natural fertilizers such as manure and compost have been used since the earliest days of farming.
1. pesticide exposure can cause Parkinson's disease
2. pesticides are endangering the monarch butterfly
1. Although mercury is known to be highly toxic, it was considered therapeutic throughout much of history.
2. Lead has been in use by ancient civilizations for thousands of years, and is mentioned in the second book of the Old Testament.
3. Between 1979 and 2001, there were 230,000 asbestos related deaths.