Chlorine: It has a long history being used as a disinfectant, but can taint water and produces byproducts. The vapor can cause respiratory problems. Lead: This is normally found in the older houses. It can be deadly for children as it can impair learning and cause behavioral problems. Trihalomethanes: This is a byproduct of chlorine, and can cause liver, kidney or central nervous system problems. Volatile organic compounds: Another byproduct of drinking water disinfection. Alachlor: It Enters water from run-off from herbicides. It is responsible for eye, liver, kidney and spleen problems. It In addition, increases your risk of cancer. Atrazine: This originates from run-off from herbicides used on row crops. It has been associated with cardiovascular system problems and with a low sperm count in men. Benzene: It enters the ground from a factory discharge and leaching from landfills. It is known to be re for anemia, deceased platelets and is a known carcinogenic. This compound is deadly even in minute quantities.>b>Cysts: These are deadly pathogens such as Cryptosporidium, which can be fatal to the young and elderly. Lindane: This comes from run-off or leaching from insecticide used on cattle, lumber and gardens. It affects the liver and kidneys. There are two main types of water purification systems, reverse osmosis and active carbon filtration. Reverse osmosis will remove nitrates, sodium and other dissolved organic and inorganic compounds. However, it will not remove all of them. This system requires something like 1 to 5 gallons of contaminated water to produce 1 gallon of purified water. Reverse osmosis can only produce a limited amount of pure water per day. These systems tend to cost a good deal more than other than comparable systems. What features do I need in water purifier is a combination of active carbon filtration, sub micron pore filter and an ion exchange. If you look for an ion exchange unit with activated alumina this will also remove fluoride. There are three different models to choose from, countertop, under the counter and whole house water purification system. The installation of a complete house system would not be that expensive, and you could take comfort in the knowledge that all the water in your house was clean and pure drinking water.