When the plastic of water bottles is exposed to light some atoms come off from it and blend with the water, so my question is which are the chemicals and its effects
It all depends on the polymer used in making the plastic bottle. I have heard that some of these chemicals you refer to are carcinogens. I won't pretend to know the formula nor the name of these carcinogens. However, the polymer must ve, to some extent, photodegradable given that the breakdown that you speak of occurs after being subjected to light. This would indicate that the polymer chain has a carbon oxygen double bond as part of the main "backbone" of the polymer and will have been formed by condensation polymerization. This may help to indicate the type or chemical that you're asking about.