Our bodies accumulate toxins and chemicals throughout our lifetime. From what we eat, to what we breath, environmental toxins like lead, mercury and PCBs that do not easily break down can be stored in our own fatty tissues. While it is unsure whether the co-exposure of these chemicals is more harmful that to each one separately, a new study shows that several risk factors are associated with a higher chance of median blood levels for these contaminants. In an analysis of data on over three thousand women, Brown University researchers concluded that all but 17.3 percent of the women aged 16 to 49 were at or above the median blood level for one or more of these chemicals, which can then passed to fetuses and babies.