Where did the problem with the formaldehyde occur

Formaldehyde can be added as a preservative to food, but it can also be produced as the result of cooking and smoking. Formaldehyde also occurs naturally in the environment. Humans and most other living organisms make small amounts as part of normal metabolic processes. Formaldehyde is also a byproduct of combustion. When burning natural gas, kerosene, gasoline, wood, or tobacco, formaldehyde is produced. Automobile exhaust is a common source of formaldehyde in our environment. Tobacco smoking in the home is another source of the chemical in the indoor environment.

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