mos 3344 ch.6

acute toxicity chronic toxicity local toxicity

acute toxicity —an effect that manifests itself immediately following exposure or very shortly thereafter chronic toxicity —an effect that manifests itself some time after the exposure (possibly months or even years) local toxicity —the effect of an exposure at the point of contact systemic toxicity —an effect that occurs at some location remote from the point of contact

control of exposures

engineering controls administrative controls —personal protective equipment (PPE) personal hygiene practises medical surveillance refer to figure 6.2 page 160 for engineering, work practises, and medical control measures

inorganic solvents (2 categoiries)

fall into 2 classes: acids and bases acids —most common include HCL, sulphuric acid, and chromic acid, are highly corrosive and are used for refining na processing metals, usually cause burns bases —also referred to alkalis, these chemicals include potassium hydroxide, sodium hydroxide, and sodium chloride

biohazards

hazard created by exposure to biological material, include mould, fungus, bacteria, and viruses

chemical agents

hazards created by one or more chemicals

8 general characteristics or properties that make solvents effective but at the same time hazardous and toxic

low surface tension high vapour pressure low boiling point low heat of vaporization high volatility ability to dissolve fats flammability vaporization

organic solvents biological agents

organic solvents —manufactured by combining carbon with other elements biological agents —natural organisms or products of organisms that present a risk to humans 2 most common diseases resulting from biological agents are Legionnaires' disease and aids

ototoxicity

ototoxicity is defined as having an adverse in harmful effect on the nerves and or bones required for hearing and balance

skin absorption

refer to p.151 for how blisters are formed

chemicals may enter the body by 4 routes of entry:

respiration (inhalation), skin absorption, ingestion, and skin penetration

synergistic effects occur when

the result of two factors taken together is greater than the sum of the two

aerosols

—airborne respirable contaminants, such as liquid droplets or solid particulate, dispersed in air, that are of a fine enough particle size to remain suspended for a time

the potential degree of seriousness of the hazard is determined by its

toxicity or its explosive properties which are defined in terms of flammability and reactivity chemicals exist in 3 stages: solid, liquid, gas

inhalation

5 basic levels of protection or defence within the respiratory tract: the nose, which is lined with hairs called cilia which act as a coarse filter medium, the second is the interior of the nasal passage where turbinates are found turbinates (spiral or spongy sections of the respiratory system that have a centrifugal effect to help remove aerosols, act as humidifiers and heat exchangers third is father back in the throat, where the hairs or cilia are coated with a thick fluid called mucus which traps the finer particles fourth level is the lung passages such as the bronchi and the bronchiole fifth level consists of myriad tiny air sacs, called alveoli located at the ends of the lungs' air passages, called the alveolar ducts these sacs contain small cells called macrophages, which dispose of any impurities via the lymph system

dose

dose —the degree of exposure and possible reaction with time, usually the basis for the values that are developed for threshold limit values

7 types of contaminants:

dust, fume, smoke, mist, vapour, gas, liquid

low surface tension high vapour pressure low boiling point low heat of vaporization high volatility ability to dissolve fats flammability vaporization

low surface tension —allows a solvent to spread evenly and quickly to provide excellent wetting of the contact surface high vapour pressure —increases with temperature; this in turn increases the volume or concentration of a generated vapour or gas low boiling point —the lower the boiling point (temperature at which the vapour pressure of a liquid equals atmospheric pressure), the greater the rate of evaporation or generation of vapours from a liquid, useful when cleaning or painting b/c the solvents can evaporate quickly at room temperature, allowing the article to dry or tack off efficiently low heat of vaporization —the amount of heat or energy required to change a liquid into a gas or vapour...the less heat required high volatility —the main test of a solvent's effectiveness is the speed at which it will evaporate, the greater the volatility, the faster the evaporation and the greater the health and fire risk ability to dissolve fats — when solvents are in contact with the skin, the skin's surface oils are dissolved, unprotected skin becomes susceptible to infection and other trauma, skin contact with solvents is one of the major causes of dermatitis (the inflammation of the skin from any cause) flammability —one of the main hazards associated with solvent use, since all organic solvents are flammable chemical specifications usually list 4 characteristics that relate to flammability: flash point —the lowest temperature at which a liquid gives off enough vapour to form an ignitable mixture with air and produce a flame with a source of ignition lower explosion limit —the smallest fuel-air mixture that is ignitable, expressed as a percentage upper explosion limit —the highest fuel air mixture that is ignitable, carbon monoxide is 74% auto-ignition temperature —the lowest temperature at which a flammable fuel air mixture will ignite from its own heat source refer to p.154 for classification of toxic substances (12) vaporization —most solvents will form very large volumes of vapour from a small amount of liquid

ingestion

not as bad as through the skin or the lungs target organs —tissues or organs that are most affected by exposure to a particular substance surfactant layer — layer of liquids in the digestive tract and elsewhere that modify or reduce the surface tension within the conductors —intestine, blood vessels —to allow material —blood, food, stools, and so on to move easily