"PVC is unique among plastics for another reason other than the fact it contains chlorine. PVC cannot be used without a range of additives. This is because PVC on its own is unstable and must always be used with additives called stabilizers.
PVC in its normal state is hard and brittle so plasticizers are used to make the material soft and flexible while others add colour (heavy metals), or make it fire resistant (flame retardants), or protect the material from bacteria and fungal growth (biocides).
Other chemicals are also added such as antistatic compounds, optical brighteners, impact modifiers and anti-oxidants. Of the many thousands of additives used with PVC, 150 are used in significant volumes.
These additives were originally developed to make PVC a marketable commodity- since it was essentially a waste product - but they may now in fact comprise more than 60% by weight of a finished product!
What happens to these chemicals when they are used to make different PVC products? They may be washed out (leached), lost to the air (volatilization), consumed by microbes (for this reason PVC sometimes contains 'biostabilizers', usually containing heavy metals); or they may pass into other materials by direct contact (migration). Whatever the case, PVC additives have now contaminated the environment on a global scale.
For instance over 1 million tonnes of plasticizers are used in western Europe annually, which 77% are used in PVC production. By far the most important plasticizer is Di-2-ethylhexyl- phthalate, commonly known as DEHP.
Total world annual production of this substance is estimated (1987) at between 3 and million tonnes. 1 Most is used for PVC production. It is now found everywhere in the environment (in Atlantic fish, bird eggs, marine mammals, corn plants) and is suspected to cause cancer in humans, according to USA research. DEHP is released in significant amounts into the environment throughout its whole lifecycle: 1% during production (mainly in waste waters); 0.05% during distribution; 1% during plastic blending, and further amounts from PVC products during use and disposal. 2
The migration of DEHP and similar plasticizers from cling film into foods, especially fatty foods such as dairy products, has led many manufacturers to offer non-PVC film. In Austria, DEHP is banned in packaging that has direct contact with food. In Switzerland, the use of DEHP for the manufacture of toys for children aged less than three years was banned in 1986, and in Germany its use in teething rings is 'not recommended'. In the Netherlands the potential ecotoxicological consequences appear better recognised - DEHP is on the priority list of environmentally toxic substances. It is also a priority pollutant in the USA. 3
Because it is to a limited extent water soluble, DEHP is carried with effluents into sewage plants, where it accumulates in sewage sludges and contaminate what could be a good fertilizer and soil conditioner. It is also fat soluble and will be absorbed into fatty products with which it comes into contact. Softening agents are therefore present in blood stored in PVC blood bags and consequently in the blood of patients who have received blood transfusions and of dialysis patients, and in food-stuffs which have been in contact with PVC (see Factsheet 6).
As with the plasticizer DEHP, the PVC industry supports other toxic industries. For instance foaming agents are used in some PVC products to economize on materials, to facilitate shaping car dashboards) and in the manufacture of upholstery. Eighty- five percent of all chemical foaming agents are used for PVC products. 4
PVC is inherently unstable and must there nearly always be used with additives known as stabilizers. This is not true of other plastics. Stabilizers are based on heavy metals: lead was the earliest, but cadmium, tin, barium and zinc are also used in large volumes.
Heavy metals are toxic not only to humans (bioaccumulation with severe organic consequences) but also to ecosystems."
- from:
http://www.mindfully.org/Plastic/PVC-Disguise-Greenpeace1992.htm#2
Keep in mind, most tests are in mind of open systems where water cah drain into a sewer, not get recirculated/trapped in a system.
White PVC is Sch40 or lower. Light grey is Sch40 electrical conduit. Dark Gray is Sch80 pipe--heavier duty. 
