This is a photo from one of the lactation stations in the University of Washington Health Sciences building. There is something seriously wrong with this picture. But we’ll get to that.

Writing from a hotel room, my toddler is fast asleep. She spent the better part of the evening tearing around the room, in a fashion appropriate for a young child who’s routine was thrown off from a day of travel. When her mad dashes were finally interrupted by bath time, we noticed the telltale red speckles of a skin irritant dotting her feet, legs and arms. My best guess—some sort of cleaning solution used in the hotel room left a residue that her delicate skin gobbled up.

In public health, young children like my daughter are labeled as a “vulnerable population.” This is in part due to their young immune systems, still ill-equipped to deal with many of the viral and bacterial hurdles that the experienced immune system of a healthy adult takes in stride. But this is also because children receive a proportionately higher “dose” of their environment. Young children are closer to the ground where many contaminants lie, and they stick more of said ground in their mouth. This is especially true of toddlers and babies, for whom hand-to-mouth play is so critical for development and learning about the world around them.

The WHO and EPA estimate that young children consume between 100 to 400 mg of soil per day, compared to about 50 mg for adults. Factor in average weight for adults and young children, and the numbers tell a pretty straight forward story—kids eat way more dirt that their parents, and as a result, are at a higher risk for any effects the content of that dirt may have.

Dirt is one thing. We all need a little dirt. But in our modern age of contaminants, it’s what is in that dirt that is concerning. Whether it’s a residue of nasty cleaning products lingering on the floor of a hotel room, lead sloughed off from damaged paint, pesticide overspray that you found yourself downwind of, or even Lysol, kids get a proportionately higher dose than adults.

My feet paced over the same hotel floor. But my daughter rolled, crawled and tumbled through chemical residue. Her bath washed some of it away, and her body will process some of the toxins out of her system while she sleeps. But some of those lovely contaminants will find their way into her body and lodge themselves in her adipose tissue — information about her environment that will be stored away for another day. This is where things get interesting.

(Find Part 2 here…)