PCBs and mercury are two of the most dangerous contaminants in SF Bay waters. PCBs are known to cause cancer and other health risks while mercury is known to harm the brain and the nervous system. Since we consume wildlife from the SF Bay, it is important to be aware of the potential contaminants that the wildlife may contain.

If we were to compare PCB and mercury concentrations in fish tissues and sediments through 1980-2018, we can see from the graphs that PCB contamination is much more potent than that of mercury. More importantly, it's interesting that most of the contaimination exists in fish tissues instead of sediments. (Note: results are normalized to reduce bias with testing frequency).

It is important to note from the graph above that peaks in contaminants' concentration occurred around 2003-2004, but ever since, there is a clear and conscious effort to reduce such contaminants, as evident by the graph.

Surprisingly, when we normalize the data by region (instead of by year), the outliers from 2003-2004 are reduced, and we see that, overall, it is more common to find mercury contaminations, especially in South SF Bay and San Pablo Bay. Another consistent pattern is that mercury tends to be prevalent in both fish tissues and sediments across the Bay while PCB isn't found commonly besides Central SF Bay.

Knowing that the SF Bay waters are not completely clean of contaminants, what does this say about the types of fish that we can safely consume? Let's take a look at the species to avoid based on contaminants' concentration. The Office of Environmental Health Hazard Assessment recommends that fishes are fully grilled or cooked before consumption to reduce chemicals. For the most part, PCBs can be cooked away while mercury cannot be removed through cooking.