The meaning of the word plastic implies flexibility. In order for a substance to change shape its molecules must be free to move about. As we know from personal experience, warm or hot plastic is more flexible than when it is cold. Its molecules are more loosely bound to one another as temperature increases. You can smell the plastic in your car after it is parked on a hot day (and the seats are softer). Plastics that are soft or flexibile when cool are thus far more prone to out-gassing than hard ones. And then there is the type of plastic itself. Some are very toxic, and on the other end of the spectrum, some are quite inert. Plastics that must be flexible and inexpensive, like carpeting, packaging, latex paint, and auto interiors can be quite toxic. Most people live amid these elements everyday, and so do their birds. When these plastics are new and when they are warm or hot, the dangers are much higher. Hot coffee in a styrofoam cup is insane. We have all seen what happens when plastic is left in the sun. It becomes brittle. Its plasticity goes away (into the air or water around it). This process is happening to ALL plastics (and many other substances as well), but at differing rates.
Sports bottles can be dangerous, however ones made of Nalgene are very stable (and more expensive). Water in Nalgene, if kept below 70 degrees, is probably safer than bottled water in a cheap plastic container at a much cooler temperture. Are you buying distilled water for safety? Does it come in cheap plastic bottle? Does your household water come via plastic pipes (most municipal water) or metal pipes (if so, what kind of metal)?
The main thing to remember is that plastic toxicity is measured in parts per million (ppm). To keep the ppm at the lowest rate, assure that the water or air is freely moving and as cool as is practical. Out-gassing into water or air is taking place at a given rate according to the type of plastic and the ambient temperature. It is good practice to let your water run for a few minutes each morning to rinse the pipes of the accumulated contamination (pipe tea) from it sitting still overnight (steeping). And assure there is plenty of room air exchange with outdoor air to reduce the contamination build-up from out-gassing of carpeting and the many other plastic items in your home. Where possible, total removal of carpeting is the best practice.
The ABS plastic that we use for our products is one of the most inert plastics. Even at 100 degrees F there is nearly no outgassing or change in it's flexibility. It is not very flexible. We use a bonding agent to "weld" the seams instead of "glue" because the bonding agent gasses so fast that non is present in a short time. This is true of our nest boxes. The ABS plastic poses no health hazard whatsoever and offers many safety advantages over metal or wood.
So there are plastics and there are plastics. Please carefully consider what plastics you bring into your birds lives. They are the Canaries in the mines and their sensitivity may save your life.China Prairie Company