Question

1. Exposure/dose:

a. Define and discuss the significance and differences between exposure-response evaluation and dose-response assessment.

b. Give an example of how each would be used.

2. Define the following terms and describe how they are used.

a. RfD

b. RfC

c. NOAEL

d. LOAEL

e. MDD

3. Formaldehyde is a chemical that has been known to be present in certain types of flooring.

a. List the chemical properties of formaldehyde.

b. List the physical properties of formaldehyde

c. List the toxicological properties of formaldehyde.

d. What are the pathway(s) of exposure to formaldehyde as a result of its use in interior finishes and the risks that people may be exposed to, if any.

Answer 1

b) Formaldehyde is a colorless gas with irritating and strong odor. It can be present in many forms as gas (natural state), solid as paraformaldehyde and as aqueous solutions in the form of formalin - formaldehyde in methanol or water and aqueous solution of paraformaldehyde. It has boiling point of -21degree celsius. It is completely soluble in water and up to 55% soluble in ether, acetone, benzene, and alcohol.

c) Toxicological properties of formaldehyde

• Formaldehyde interacts with the molecules on cell membranes and in tissues and nucleic acids, inturn disrupts cellular functions. Its high concentration precipitates proteins resulting cell death.
• It is rapidly absorbed in the respiratory tract as well as in GIT leading to the formation of formic acid and hence imbalances the pH, disrupting cell functions
• It is associated with respiratory sensitization, contact dermatitis and cancer.
• It is classified as senstizer, as its exposure to the skin results in primary skin irritation and allergic dermatitis.

d) Formaldehyde is used in the production of adhesives used in fiberboard and particle board, and is also found in foam insulation and textile finishing treatments. Formaldehyde sources include furniture and wooden products containing formaldehyde-based resins, paints, wallpapers, glues, adhesives, varnishes and lacquers; household cleaning products such as detergents, disinfectants, cosmetics such as liquid soaps, shampoos, nail varnishes, insecticides and paper products.

• Formaldehyde is rapidly absorbed in the respiratory and gastrointestinal tracts and metabolized to formate in the upper respiratory tract.
• It can penetrate human skin and induces allergic contact dermatitis.
• Inhalation of formaldehyde leads to the formation of DNA–protein crosslinks in cells at the site of contact.