Figures 7-6a and 7-6b illustrate that the choice of scales to use for each can greatly affect the graph’s appearance. Testing with consumers is required to assess the impression made by alternative formats.
The scales used in Figure 7-6a have the effect of emphasizing information on EPA/DHA content and illustrate that there are a number of seafood choices, with varying levels of EPA and DHA, available with low exposure to methylmercury. The figure does not provide information about levels of lipophilic contaminants such as dioxins and PCBs because of the limited availability of data for various types of seafood. However, evidence presented in Chapter 4 suggests that levels of these contaminants in commercially obtained seafood do not pose a risk of adverse health effects even among the most at-risk groups, i.e., females who could become pregnant, are pregnant, or are lactating, and infants and young children, when consumed in the amount of two 3-ounce servings per week. As shown, Figure 7-6a may be appropriate for guidance to females who could become pregnant, are pregnant, or are lactating, and for infants and young children, as the shaded bars indicate types of seafood that should be avoided or consumed in limited amounts by individuals in these target populations. For adolescent males, adult males, and females who will not become pregnant, Figure 7-6a could be used for guidance without any specially shaded bars.
Figure 7-6b uses alternative scales to show the methylmercury and EPA/ DHA content in 3-ounce servings of different seafoods. The design tends to emphasize the methylmercury and deemphasize the EPA/DHA information. A side-by-side comparison of Figures 7-6a and 7-6b illustrates the impact of design choices on how consumer guidance information is presented. The committee again emphasizes that the scales used in Figures 7-6a and 7-6b for EPA/DHA and methylmercury content are arbitrary. Designers will need to carefully test the effect of the scales used for the bars on the message received by consumers.
Figure 7-7 also provides information on both EPA/DHA and methylmercury content, although for a smaller number of seafood choices to make the figure easier to read. The figure’s advantage is that it combines information on one and two 3-ounce servings per week. The corresponding disadvantage is that it may be harder for consumers to grasp. Graphs like this can be helpful in identifying product consumption patterns that provide benefits with little risk to most consumers as compared to those that raise risk concerns for some consumers. Figure 7-7 may be useful guidance for females who could become pregnant, are pregnant, or are lactating, and for infants and young children. If the EPA/DHA-methylmercury tradeoff is less important, for example, for adolescent males, adult males, and females who will not become pregant, then Figure 7-5, which focuses solely on EPA/DHA content, may provide more useful guidance. Here, the committee again notes that the choice of scale on the horizontal and vertical axes may