Can pollution and things in an organism's environment serve as hormones?
A hormone is defined as "a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism" (I'm just taking Wikipedia definition).
Hormones work by binding to specific receptors present on their target cells so, if there is something in the environment that mimics the hormone, by binding to the same receptor they can act as hormones: these substances are called xenohormones and can often act as endocrine disruptors compounds (EDC), by acting on various organs in the body.
Probably the most known xenohormones are xenoestrogens that are been studied as possibly harmful for human health (e.g. linked to breast cancer), and as an environmental hazards, as they can, for instance, cause reproductive problems in fish.
Xenohormones are not necessarily bad, though. Some analogs of human hormones are used in therapy, having being synthesised specifically, for instance, to have higher potency then their natural counterparts.
Sure. Here are two anecdotes on xenohormones from unlikely sources.
In the 1940s, Merino ewes imported to Australia were found to be infertile, as well as sometimes having stillbirths. A bit of detective work showed that the reproductive disorders observed were due to isoflavones like formononetin found in the clovers (Trifolium spp.) that the Merino were grazing on. Due to the insufficient amounts of needed minerals in the soil, the clover plants were producing the phytoestrogens to defend themselves (sterilize your predators, and there will be less of them eating your kind). (1)
In the late 1950s, it was observed that Indiana sows feeding on moldy corn were exhibiting symptoms including engorgement of the vulva and stimulation of the mammaries. Researchers at Purdue University found that Fusarium (Gibberella) molds in the corn were producing a mycoestrogen, zearalenone, that were triggering those symptoms in swine. (2)
Yes, they can.
An example of a man-made chemical byproduct affecting hormone signaling is Bisphenol A (BPA). There is a vast body of evidence linking BPA to all manners of hormonal misregulation.
It would be impossible to try and enumerate all of the studies, and specific mechanisms or the extent of the signaling pathways impacted by BPA have yet to be clarified, however you can have a look to the huge amount of papers on the matter that you can find on Pubmed.