Why were polio epidemics in this country uncommon prior to the 1900's?

What disease was the first to be identified as a waterborne disease?

Giardia Lamblia; it was discovered by Leeuwenhoek.

Identify the cellular process that is disrupted by the bacterium that causes cholera.

Why do you think it is important to perform water quality tests frequently, especially in areas where there is a probability of waterborne disease?

How are pcb's (polychlorinated biphenyls) affecting the orca populations in Washington State. These pcb chemicals were banned in 1977. What does this video say about why they are still a problem?

PCB's cause cancer - they build up in food webs (bioaccumulate) and orca's are usually at the top of the food webs. If there are contaminants in the wild fish that humans...