This figure shows some common sources of mercury, the conversion to toxic methylmercury and the outline of EPA consumption recommendations for certain types of fish based on mercury levels.
The original caption stated: "Mercury from coal fired power plants and other sources travels through the atmosphere and water. Some is changed to methylmercury, which can enter the food chain to be concentrated at each step on that chain. Large old predators like sharks and pike, or scavengers like halibut, hold the greatest concentrations of mercury. The mercury is particularly problematic during development, so these limits here are designed to protect women who might become pregnant and children 12 or younger."
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<span class="int-own-work" lang="en">Own work</span>; translated the English version