Any form of ascorbic acid or vitamin C could cause health problems if ingested in large amounts. Unless you work with ascorbic acid in an industrial setting, your chances of exposure to toxic amounts of powdered vitamin C are small. If you can your own fruits and vegetables, you can use powdered ascorbic acid to preserve the color and freshness of home-grown produce. Using powdered ascorbic acid safely requires only a few basic precautions.
If your diet includes plenty of fresh fruits and vegetables, you should get enough ascorbic acid from food to satisfy your daily needs. Vitamin supplements supply vitamin C in convenient doses from 25 mg to 1,000 mg. Adult men need at least 90 mg daily; adult women need at least 75 mg. Children might need only 15 mg per day. Taking more than 2,000 mg daily causes digestive distress and diarrhea in adults. Children tolerate less. The University of Maryland Medical Center recommends that you ask your family physician for advice before taking more than 1,000 mg of vitamin C yourself, and before giving extra vitamin C to your children.
Ascorbic acid oxidizes quickly if dissolved in water or exposed to humidity. Many supplements provide vitamin C as a dry solid to safeguard potency and increase shelf life of the product. Capsules or chewable tablets of vitamin C store well if protected from moisture, light and heat. Some vitamin supplements supply vitamin C as powder, but already mixed with other ingredients. A spoonful of powdered supplement adds a safe amount of ascorbic acid to your breakfast juice, but one teaspoon of pure ascorbic acid crystals supplies 3,000 mg vitamin C, enough to make an adult ill.
Powdered crystalline ascorbic acid stores conveniently and allows accurate measurement and mixing for use as a food additive. Placing produce in ascorbic acid solutions prevents fruits and vegetables from browning after cutting and peeling. You run a much higher risk of toxic exposure to powdered ascorbic acid if you work in food processing or in the manufacture of pharmaceuticals. Ascorbic acid dust in the air causes sore throats and coughs, reddening of the skin and eyes, and eye pain. Rinse your mouth and eyes with plain water if you're exposed to ascorbic acid dust. Seek medical attention for eye irritation.
If you use crystalline vitamin C at home to improve the quality of your home-canned foods, an accidental spill could expose you and your family to toxic ascorbic acid dust. Misting the spilled powder lightly with water keeps dust out of the air, but wear a particle mask for extra safety. Wear rubber gloves during cleanup and sweep the spill carefully into a container. Wash the spill area afterward with clean water. Don't flush waste ascorbic acid down the toilet. Add the powder to damp cat litter and seal the mixture in doubled plastic bags. Put the sealed double-bag in your trash for pickup, the Hazardous Substances Data Bank recommends.