Inhalation

You begin at 250 degrees Celsius.

Below that threshold you were the wall. PVC siding, white, south-facing, thirty-one years of ultraviolet exposure having accomplished nothing the fire will accomplish in four minutes. The polymer chains hold until they don't. At 250 degrees the chlorine atoms detach as hydrogen chloride gas. The carbon backbone collapses. You are one of the fragments: sixty nanometers of black carbon carrying chlorinated compounds that required the fire to exist. Methyl chloride. Vinyl chloride. Chlorobenzene. None of them were in the siding. None of them existed ten seconds ago.

The house has more to give. At 300 degrees the polyurethane foam in the attic decomposes, releasing isocyanates and a yellow smoke that smells like nothing a forest produces. At 600 degrees those isocyanates fragment into hydrogen cyanide. The treated deck lumber surrenders its chromium and arsenic. The electronics give up copper, zinc, lead. Flame-retardant in the children's mattresses releases polybrominated diphenyl ethers. And from the combination of carbon and chlorine at temperature: dioxins, specifically 2,3,7,8-tetrachlorodibenzo-p-dioxin, molecules that existed in no material in the house and exist now only because the house is burning. No forest fire yields you. You carry a thousand times more hydrogen chloride than any particle a Douglas fir could, and dioxins at concentrations a forest fire would need a hundred thousand times the fuel to generate. You carry a chemistry that trees cannot make.

Convective heat lifts you in a column of combustion gases. As the plume cools, heavier molecules condense onto your surface. Polycyclic aromatic hydrocarbons settle into your carbon lattice: chrysene, benzo[a]pyrene. Your carcinogenic load is now roughly twenty times that of a particle born from burning Douglas fir. The plume flattens at the inversion layer and drifts southeast across the development, across a four-lane road, across the parking lot of a grocery store where the asphalt holds the day's heat and bags are being loaded into a trunk and the air is 34 degrees and carries an acid sharpness underneath something sweet and chemical, a combination the tongue tries to sort and cannot because no living body has ever had a name for the taste of a burning house, and you enter past the nostrils, past the turbinate bones that catch larger particles and route them to the throat in mucus, but you are too small for impaction, sixty nanometers passes the nasopharyngeal region the way water passes through chain-link, past the pharynx, the larynx, into the trachea where the mucociliary escalator moves its carpet of mucus upward trapping what it can, but you are smaller than the spaces between cilia and at your size the dominant force is Brownian motion, the random collision of gas molecules batting you deeper with each impact, and the airway branches and branches, twenty-three generations of branching, each passage narrower, the air slowing, the walls closer, and you are still descending past the terminal bronchioles where the last cilia stand into the respiratory bronchioles where the walls open into thin sacs and the air barely moves and you drift by diffusion, sideways, until you touch the wall of an alveolus, one of four hundred eighty million, seventy square meters of surface folded into a space the size of two fists, each alveolus wrapped in capillaries so narrow that red blood cells deform to pass through, and the barrier between air and blood is a single Type I pneumocyte stretched to twenty-five nanometers in places, thinner than the wavelength of visible light, and the cell takes you in through the cell itself, the membrane wrapping around you, pulling you into the cytoplasm in a vesicle, the tight junctions between cells sealed shut, carrying you through and releasing you on the other side where the capillary blood is waiting, where gas exchange reaches equilibrium in a quarter of a second, where the distance between air and blood has always been as little as two tenths of a micrometer, which is to say the barrier between the atmosphere and the interior of a living body has always been almost nothing, a membrane so thin it cannot be seen with light, and now the almost-nothing has been crossed and the blood carries what it received within sixty seconds, carries it past the heart and into systemic circulation where it distributes to the liver, the spleen, the bone marrow, and a fraction of what was deposited in the nasal passage takes the older pathway, the one that bypasses blood entirely, traveling up the olfactory nerve from the mucosa directly into the olfactory bulb, arriving in brain tissue within hours, and none of this registers as sensation, none of this trips an alarm, because you were built to exchange gas across that membrane and the membrane does not distinguish, and you will not feel the particles peaking in your blood between ten and twenty minutes while you settle the bags so the eggs sit flat, will not feel the ones your kidneys filter into urine pooling against the epithelium of your bladder, or the ones the mucociliary escalator caught and carried upward and you swallowed into your stomach and intestine where their cargo dissolves against the wall of your proximal colon, and you will not feel the benzo[a]pyrene releasing from its carbon carrier in the warm pH of your blood, entering a cell in your lung epithelium where cytochrome P450 enzymes, the ones your body makes to metabolize foreign compounds, convert it to benzo[a]pyrene-7,8-diol-9,10-epoxide, which binds directly to your DNA, forming an adduct at guanine, bending the double helix at the point of attachment, and when the cell divides it reads the damaged template and writes a thymine where a cytosine should be, a G-to-T transversion, and if this happens at codon 248 or 273 of the TP53 gene, the gene whose only job is to tell damaged cells to stop dividing, the cell that should have stopped does not stop, and meanwhile the dioxin from the siding is activating the aryl hydrocarbon receptor which upregulates the very enzymes that convert benzo[a]pyrene to its carcinogenic form, so two compounds from two different materials in the same burning house cooperate inside your cells in a way they never cooperated inside the wall, the dioxin accelerating the machinery that makes the PAH lethal, while in other cells the benzo[a]pyrene is rewriting methylation patterns across your genome, silencing tumor suppressor genes by adding methyl groups to their promoters, stripping methyl groups from proto-oncogenes to wake them, and none of this will be visible for years, not in any scan or blood draw, not until a cell in your lung or your bladder or your colon or your breast or your bone marrow divides once more with its altered instructions and the doubling begins, the doubling that will carry a name, a name whose connection to smoke like this has only just begun to be traced, though the name will not remember the parking lot or the Tuesday or the four minutes it took a house to become something that entered you before you decided to let it in.

You close the trunk. Your throat is tight. Saliva thickens at the back of your tongue, metallic, and you swallow without thinking, which carries the last of what the cilia caught into your stomach. You hold your breath for a moment, though you are not sure why.

Then you breathe.