I WOULD LIKE TO REPORT THAT IT takes two hours to jog around the periphery of the Mall of America, the nation’s largest indoor shopping center in Bloomington, Minnesota. The two hours includes circumnavigating the mall’s 520 stores along with its 20,000 parking spaces, which are mostly contained within orbital rings of monumentally sized parking garages.

I began this run early in the morning and, during my circuit, saw one other human being: a man with a cigarette standing against the largest expanse of brick wall I had ever seen. Near him was a door with no doorknob. From the depths of the parking garages, a few car alarms pulsed, some near, some far, like foghorns. The wind that pours through the loading docks of the Mall of America is fearsome. It slowed my progress considerably.

When I returned to my room in the Ramada Inn — which required crossing fourteen lanes of traffic — it was almost time for my keynote address at the twenty-first annual North American Hazardous Materials Management Conference. I don’t believe its organizers intended to make an ironic statement with their choice of venue. They seemed a sincere, overworked lot. They probably figured that the continent’s hazardous-materials managers might appreciate the chance to get an early start on holiday shopping.

Ten years ago, I published a book called Living Downstream that was about, among other things, hazardous materials. Ever since, I’ve received invitations to speak about the topic. Wherever I go, I do two things. One, I look up the Toxics Release Inventory for my host-community’s zip code. I study the location of the dumps, the routine chemical emissions, the accident reports, the off-site transfers, the permitted releases. And then, once I get there, I run.

Both rituals are ways of paying attention. When I run, I can feel the slope of the land under my feet and figure out how water flows here. I notice the decrepit apple tree that means this subdivision was once an orchard. I notice the aluminum smelter’s proximity to the floodplain. Sometimes the names of streets — Creamery Road — provide clues. Sometimes a windbreak of trees does. Even when I’m completely confounded — I cannot tell you how groundwater flows beneath the Mall of America — I discover something amazing. Once, in Livonia, Michigan, while running beside glass office complexes with glabrous names like Techtron and VisTaTech, I veered off toward a small scrim of woods. Within it, three derelict buildings flanked a derelict tennis court, its green surface shattered by sprouting trees. One of the buildings was entirely filled with chairs. The other was entirely filled with bicycles. Birds flew in and out of slumping holes in the roofs.

DURING THESE TEN YEARS of running and speaking, I’ve noticed two opposing trends. The first is that people increasingly believe that their health is affected by hazardous materials in the environment. And they know a lot more about hazardous materials. Pesticides in strawberries. Lead in lipstick. Bisphenol A in water bottles. But there is decreasing knowledge about the actual environment itself. Public awareness is specific to chemicals in consumer products — which are produced elsewhere (increasingly China) and brought into our homes. The location of those homes on former orchards (where arsenical pesticides were used) or near old toxic-dump sites (where drums of solvents were buried) — these matters seem blurrier and blurrier to the folks in my audiences. In fact, I’ve had to start explaining the word “Superfund,” as it doesn’t seem to ring any real bells for a lot of people — including people in communities where Superfund sites are present. (Superfund sites are the nation’s worst toxic-waste sites. There are 1,305 of them, and they are named for the “super” fund of money put together by Congress in 1980 to clean them up, a trust that went bankrupt five years ago.)

I was recently invited to Rockford, Illinois, to speak about toxic chemicals. That seemed appropriate because Rockford is the site of a longstanding Superfund site. Solvents used by former businesses had drizzled into drinking water wells. Rockford is famous within toxicology circles because of the bladder-cancer cluster that was discovered here and because it was here where researchers figured out, in the 1980s, that the level of solvents in human blood is predicted not by the amount of water drunk from the tap but by the length of “shower run times.” In other words, inhalation is a bigger route of exposure to solvent-contaminated drinking water than drinking it, and showering provides the biggest dose. And yet only two people in my college audience knew about these studies — or even knew that Rockford had a Superfund site. Even the local emergency-room physician hadn’t heard the news.

WHAT’S INDUCING THIS EPIDEMIC of environmental amnesia? Maybe one contributor is the long silence of the federal government on environmental catastrophes of all kinds. In the breach, activist groups have tried to protect the public. In need of positive messages and deliverable results, they focus on individual solutions. Don’t microwave in plastic. Buy organic. There is no place in that discussion for the barrels of waste buried atop the aquifer. The very mention of them fills a room with paralyzing despair.

Or maybe we’re now spending so much more time with consumer objects than with our natural environments that we have forgotten how to think about them. Sport water bottles are real to us — polycarbonate? or stainless steel? — but creekbeds are fuzzy concepts.

Or maybe our unremembering is a wall against grief. My own elementary school — along with the field, playground, and wooded path to the crosswalk — was razed years ago to make way for discount shopping. I have steadfastly refused to frequent that part of town. But when my son needed a haircut for my father’s funeral, I found myself driving my old walking route to school, in search of a salon open on a Monday. It was supposed to be in here somewhere. While navigating the service roads, I tried hard to forget. But while my son was being pumped up in his pneumatic chair, I saw reflected in the mirror a retaining wall at the edge of the parking lot. I know that pattern of stones. I looked at them every day during math. I was standing in my fifth grade classroom. And the military recruiting center next door would have been the lunchroom. And that drive-through over there was the field where, every recess, my sister and Danelle and I ran, circling and whinnying like wild, wild horses.