Bioaccumulation of Heavy Metals

Recall from Chapter 10 that some substances display the phenomenon of biomagnification: Their concentrations increase progressively along an ecological food chain. The only one of the five heavy metals under consideration that is indisputably capable of doing this is mercury. Many aquatic organisms do, however, bioconcentrate (but do not biomagnify) heavy metals. For example, oysters and mussels can contain levels of mercury and cadmium that are 100,000 times greater than those in the water in which they live.

The concentrations of most heavy metals in drinking water are usually small and cause no acute health problems; however, exceptions do occur and will be discussed later. As is the case with toxic organic chemicals, the amounts of metals that are ingested through our food supply are usually of much greater concern than is the intake attributable to drinking water. Paradoxically, the heavy metals in the fish that we ingest usually originate in fresh water.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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