Part 6: Practice
Dr. Meg Christensen is the founder of Interior Medicine, a physician-created resource on non-toxic home products and household exposures. Her layer-by-layer analysis of materials and products draws on her background in medicine, biochemistry, epidemiology, and clinical research.
Answer capsule When the label tells you nothing, the chemistry still does. This section is all about predicting whether ingredients in a product are able to impact you. How to predict what a material releases into your home and whether it can reach your body, just from knowing what it's made of. It helps you predict what materials have what types of chemicals in them. Second it walks you through basic chemical behavior as a way to predict if a hazard is actually becoming an exposure.
Soup Ingredients
Most products don't come with an ingredients list. Sometimes you get a Prop 65 sticker, sometimes you just know there's lead in an old vintage lamp because everything from that era had lead in it. Either way you've got a named hazard with no clear sense of whether it should actually worry you.
This section helps you decide by predicting chemical behavior from the material itself. You don't need a chemistry degree, and we'll walk through the patterns so they're clear.
Remember this from Part 4? VOCs, sVOCs, and particles, the three categories that describe how chemicals leave the materials they're embedded in, where they end up around your house, and which routes they take to reach your body. A VOC drifts off as gas and rides the air into your lungs. An sVOC migrates slowly out of plastic or foam, settles into household dust, and gets swallowed when that dust lands on hands or food. A particle stays put until it's physically disturbed, and once it is, it either resuspends into the air in chunks that are usually too big to penetrate deep into the lung or it settles on surfaces where it can later be picked up and ingested.
Lead is a clean example. Lead is a particle, which means in an old painted lamp it sits there until something disturbs it (a damp cloth, a chipped edge, the normal flaking of an aging surface). It doesn't volatilize into the air on its own and it doesn't pass through your intact skin. The exposure path that matters is the one where you touch the lamp, get residue on your hand, and put that hand near your mouth, or where lead-contaminated dust resuspends and a fragment gets inhaled. That's a real route, especially for small kids who hand-mouth as part of normal development, but it's not the same situation as a substance that fills the air on its own.
Formaldehyde works the opposite way. It's a VOC, light enough to leave engineered wood or wrinkle-resistant fabric without anyone doing anything to it, and indoor concentrations climb on their own when those materials are new. No friction step, no hand-mouth step, just air and lungs.
Once you know which category a hazard sits in, you know which questions to ask about it. Is the material new or old, disturbed or undisturbed? Is the room ventilated? Are there small children in the house who put things in their mouths? The category tells you which conditions matter and which ones don't, and that's the foundation for calming down or turning up your concern, depending on what's in front of you.
This section will also help you predict waht materials are likely to have what types of chemicals in them. A ceramic bowl doesn’t emit VOCs into the air. Glue does, though.
VOCs: Substances That Become Gas
Volatile Organic Compounds, or VOCs, are chemicals that change from a liquid or solid straight into a gas at regular room temperature. This is also called “off-gassing.” It happens automatically, without any contact, friction, or heat required. (Though heat can speed up the rate of off-gassing.)
If you've ever noticed the "new car" or "new furniture" smell, you've detected VOCs. Candle scents are VOCs, and even flowers and trees release completely natural VOCs.
VOCs move freely through indoor air. Here are some of the most common VOCs that come from furniture and decor:
Formaldehyde is a common VOC found at home that comes primarily from the glue mixtures used in pressed-wood products like particleboard, MDF, and plywood to keep the wood particles and dust in “wood shape.” This is what most IKEA and other flat-pack furniture is made out of, as well as cabinetry, and some flooring. Formaldehyde is also a component of wood glue, and fabrics are often treated with formaldehyde-releasing resins to keep them wrinkle-free.
Toluene and Xylene are common VOCs that are found in paints, stains, lacquers, and adhesives. They're solvents that keep the paint a liquid. They’re part of the reason why fresh paint has a strong smell that fades over time.
Residual Plastic Monomers & Breakdown Products: plastics release residual monomers that didn't fully polymerize during manufacturing and from degradation products as the plastic breaks down over time with heat and UV exposure. PVC (vinyl flooring, shower curtains, pipes) is the highest emitter among common household plastics. Unlike most other VOC sources, plastic emissions can increase as the material ages, because degradation creates new volatile fragments rather than depleting a fixed reservoir.
Undisclosed VOC Mixtures: Candles, air fresheners, and scented products are composed of mixtures of VOCs that are designed to smell good. This includes synthetic fragrances as well as natural essential oils.
2. sVOCs: Substances That Migrate Slowly
Semi-Volatile Organic Compounds (sVOCs) can be a little hard to wrap your mind around because their behavior is less intuitive. They’re in a separate category than regular VOCs, because sVOCs don't usually become gas and drift away. But, they also aren't locked permanently in place.
The best analogy for how an sVOC moves is like butter left on the countertop. Butter migrates onto the butter dish gradually, driven by heat, friction, and time. Likewise, sVOCs leave products slowly and end up on surfaces, in household dust, and on other objects nearby. Some common sVOCs that come from furniture, curtains, upholstery, and other home products are:
Phthalates: a type of sVOC used as a plasticizer and fragrance carrier. They are not chemically bonded to the plastic, and migrate out of it continuously. Plasticizers are added to PVC shower curtains to make them flexible and fabric-like, and were added to vinyl flooring (including “luxury” vinyl plank) until recently (though these are mostly replaced now by non-phthalate plasticizers.) Phthalates are used as fragrance carriers in candles and other scented home products.
PFAS: (per- and polyfluoroalkyl substances) are also a type of sVOC. PFAS are common in the home as surface treatments applied to upholstery, carpet, rugs, cookware, and food packaging to resist water, oil, and stains. They migrate slowly into dust and onto surfaces.
Flame retardants: added to foam furniture, mattresses, carpet padding, curtain fabric, and electronics. There are hundreds of types of flame retardants, and most of them are considered sVOCs because they’re able to migrate from products into household dust over time.
Heavy siloxanes are sVOCs that are released from silicone-containing products, including sealants, caulks, silicone bakeware and silicone-treated water-resistant fabrics over time. (Lighter forms of siloxanes can volatilize straight into the air as regular VOCs.)
Naphthalene is an sVOC that is not only the active ingredient in traditional mothballs, but is also used in the creation of caulk, carpet pads, and other building materials.
3. Particles: Physical Fragments of Things
Particles, also called Particulate Matter, PM1, PM2.5, or PM10, are solid pieces of material. Unlike VOCs and sVOCs, which are individual chemical molecules, particles are physical fragments composed of lots of chemicals. They are defined entirely by their size, not by their chemistry, and they are generated by friction, abrasion, deterioration, and combustion.
Size determines how they behave. Larger particles (PM10 and above, like dust you can see) settle out of the air relatively quickly and become part of household dust on surfaces and the floor. Fine and ultrafine particles (PM2.5 and PM1) stay airborne for hours and travel freely through the home.
Particles also act as carriers for sVOCs, meaning chemicals like flame retardants and PFAS can catch a ride on particles and move around your house that way.
Microplastics and microfibers are shed from synthetic textiles like polyester curtains, carpet, and clothing during normal use. They are a type of plastic particle released through friction and wear. Microplastics have been found in indoor dust, air, and drinking water.
Foam fragments break off from deteriorating cushions, mattresses, and carpet padding through compression and friction over years of use. Because flame retardants and other chemical additives are embedded in the foam, these fragments can carry sVOCs into dust.
Combustion particles are generated by cooking (especially frying and high-heat methods), burning candles, and gas stoves. These particles are chemically complex: they carry adsorbed organic compounds, metals, radon decay products, and other substances on their surfaces.
Heavy metals are generated when surfaces containing lead, cadmium, or arsenic experience friction, like windows being opened and closed, doors rubbing against lead-painted frames, or scraping an arsenic-containing piece of cookware with a metal spatula. Heavy metals can travel through the home as particles (paint chips and dust), on other particles (adsorbed onto PM2.5), or as particles dissolved dissolved in water. They don’t behave like VOCs or sVOCs.
Asbestos fibers are released from building materials in pre-1980 homes when those materials crumble with age or are disturbed during renovation. Intact, undisturbed asbestos materials are generally stable.
Engineered nanomaterials like nano-titanium dioxide and nano-silver are intentionally manufactured to be extremely small (1 to 100 nanometers). At this scale, they can cross biological membranes that larger particles cannot. They appear in some nonstick coatings, antimicrobial textiles, and paints. By movement behavior, they are particles. But their engineered size gives them access to biological pathways that conventional particles don't reach, which is why they are sometimes discussed as their own category.
Bonus: UVCBs, or When the Categories Mix Into Unknowns
Some substances don’t fit into any of the above categories. They’re complicated mixtures with variable, sometimes completely unknown composition. In regulatory science, these are called UVCBs: substances of Unknown or Variable composition, Complex reaction products, and Biological materials. Fragrance blends, essential oils, and paraffin wax are one of the most common types of UVCBs in homes, all parts of candles.
A single fragrance mixture might include VOCs that off-gas, sVOCs that migrate into dust, and particle-bound compounds, all in proportions that aren't disclosed and may not even be fully characterized by the manufacturer. This is a major gap in chemical regulation, and one reason why "fragrance" as a single line item on an ingredients list can represent dozens of individual chemicals moving through your home in different ways.
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