EXPOSURE CONCEPTS
ROUTES OF EXPOSURE
In a work environment where chemicals are used, an individual may potentially be exposed in three ways:
•inhalation
•skin and eye contact
•ingestion
Inhalation is the most common route of exposure for airborne particulates, gases, and vapors. Inhalation exposures are important because many chemicals that enter the lungs can pass directly into the blood stream and be transported to other areas of the body.
Skin contact can also be a significant source of exposure which can lead to adverse health effects. Some chemicals can be absorbed into the body through the skin while others may cause irritation or rashes (dermatitis). In addition, some chemicals are potential eye irritants.
Ingestion is not considered to be a significant problem in the workplace. Inadvertent ingestion of chemicals may occur if food or beverages are consumed in chemical handling areas or if good personal hygiene practices are not followed, i.e., washing hands before eating, drinking, smoking, etc.
Air contaminants: are chemicals that may be present in the air that could be inhaled and may produce adverse effects. These effects can be divided into two classes:
•acute health
•chronic health
Dose Response: All chemicals are toxic if taken into the body by the right route of exposure and at a high enough dose. As the dose increases, there is a corresponding effect or response.
Chemicals that require large doses or exposure concentrations to produce an adverse effect have a low toxicity, while chemicals that require smaller doses to produce an adverse effect are considered more toxic. For example, acetic acid is irritating to the eyes and upper respiratory system at low concentrations, about 10 ppm. Isopropyl alcohol is not irritating to the eyes until concentrations reach over 400 ppm. Based on this comparison, acetic acid causes an irritation at much lower concentrations than isopropyl alcohol.
AIR CONTAMINANTS
The air within buildings usually contains a variety of air contaminants. These contaminants can originate from outside sources (car/truck exhaust) or emissions from inside sources (office equipment, furnishings, carpet, people, kitchens, janitorial activities).
Whatever the source, contaminants in the air fall into one of two physical states of matter. They are either:
•gases and vapors, or
•solids (particulates)
Gases/Vapors: The difference between gases and vapors is their physical state at standard temperature and atmospheric pressure (STP, 22.5°C, and 760 mm Hg). A gas is in the gaseous state at STP (examples: nitrogen, carbon dioxide, sulfur dioxide). A vapor is a gas from a substance that at STP is a liquid (example, acetic acid).
Particulates: There are several
forms of particulate matter that can be airborne. These include:
•dust
•fumes
•smoke
•mists
Dust results from the application of energy to matter, by grinding, sifting pouring solids, paper cutting, etc. Dust particles have to be small enough and light enough to be airborne.
Fumes are generated by the condensation of particles in the vapor state from heated metals. Fumes are typically smaller than dust, more soluble, and are more physiologically active. Fumes are not generated during normal photographic processing operations.
Smoke results from incomplete combustion and is made up of extremely fine particles, even smaller than fumes. Smoke is extremely complex chemically, containing thousands of chemical substances. Unless something is burning, smoke is not generated during photographic processing operations.
Mists result from the dispersion of fine droplets by aerosolization of any liquid (spray cans, nitrogen agitation of tanks, electroplating). Mists can be formed during the mixing, recirculation or pouring of liquids. Mist can also be generated from foam on the surface of a liquid.
Indoor Air Quality and Ventilation in Photographic Processing Facilities • | 3 |
