Why "all wood dust is bad"

Wood dust in general is classified as a carcinogen (Group 1 by IARC, meaning known to cause cancer in humans) — not because any specific species is carcinogenic, but because chronic exposure to fine particles of any organic material increases nasal and sinus cancer risk. Beyond that, fine dust is a respiratory irritant, and some species carry extractives that sensitise skin or airways.

The worst offenders

Two species deserve special attention:

Western Red Cedar — contains plicatic acid, which causes occupational asthma in woodworkers. If you're working cedar and notice respiratory symptoms (cough, wheeze, shortness of breath), stop immediately. Cedar asthma is permanent.
Rosewood (Dalbergia) — strong sensitiser; even brief skin contact can cause dermatitis, and respiratory sensitisation is possible. Some woodworkers cannot work rosewood at all.

Cutting board safety

Open-grain species (oak, ash) harbour bacteria in their pores and are widely considered unsuitable for cutting boards despite being harder than walnut. Closed-grain species (maple, walnut, cherry) are the safe choice. The calculator flags species as food-safe or not.

Always wear a respirator

The single most important piece of PPE for any woodworker is a fitted N95 or P100 respirator. Sanding is the worst operation for dust exposure — fine particles, high concentration, easily inhaled. Dust collection helps but doesn't catch everything. Wear the respirator.

Limitations

Toxicity varies by individual. Some woodworkers tolerate "sensitiser" woods; others react to species on this list as "safe".
Doesn't account for cumulative exposure or pre-existing conditions.
Doesn't replace professional medical advice. If you have respiratory symptoms, see a doctor.
Tropical species regulations change; verify CITES status before importing exotic woods.

Frequently asked questions

Are pressure-treated woods dangerous?

Modern ACQ-treated lumber is far safer than the CCA-treated lumber of the 1990s, but the dust is still bad — don't sand treated lumber without a respirator, and don't burn the scraps. For cutting boards and food-contact projects, use untreated wood only.

Is walnut toxic to horses?

Yes — black walnut shavings are toxic to horses (laminitis risk). Walnut sawdust and shavings should not be used as horse bedding. For humans working walnut, the dust is mildly irritating but not dangerous; skin reactions are rare.

I had a reaction to a wood I worked. What now?

Stop working that species. Sensitisation is permanent — repeated exposure makes the reaction worse, not better. See a doctor if the reaction is respiratory; even mild wheezing after exposure is worth a checkup.

How do I use Wood toxicity reference step by step without mistakes?

Follow the order given in the usage section: Dust, skin and lung hazards for 14 common woodworking species. PPE recommendations and cutting-board safety notes. The step-by-step part matters less than the unit check that sits inside it. Confirm every unit matches the thing you are actually trying to measure before you press calculate - that single check catches more wrong answers than any other habit, and it costs about ten seconds.

What are the common mistakes when using Wood toxicity reference?

Most common mistakes come down to four habits: entering 20 when the field expects 0.2 because the field is a percentage; leaving a field blank and accepting the default without checking what it stands for; changing one input and reading a result that was calculated before the change; and quoting the output as an exact figure when the page describes it as a reference estimate. Press calculate again after any edit, and treat the number as a reference point rather than a final answer.