It’s one thing to worry about pollutants in our freshwater supply. It’s another to find out that all across the country, male fish swimming in some of that water are becoming “intersex,” their male sex organs producing immature female eggs. Although the condition occurs naturally in some species, it shouldn’t happen to black bass. But a new study shows that it is, and in numbers far greater than ever suspected. The phenomenon raises serious concerns about the pollution levels in our rivers and could threaten several species.