Acute Exposure is a short contact with a chemical, ranging from a few seconds to a few hours. Even though short, it may result in long-term effects, dangers, sources of pollution.
Chronic Exposure is continuous or repeated contact with a toxic substance over months or years. Some chemicals can build up in the body with a long-term exposure, causing effects possibly not seen with acute exposure.
Dose: The amount of a substance that enters or contacts a person is called a dose. The greater amount of a toxic substance that a person is exposed to, the more likely that person will suffer negative health effects. The size of the individual is a factor in calculating the dose; children or small framed adults may be affected by a lesser amount than persons with larger bodies.
Effects: A chemical exposure can produce an effect at the site of contact (local) or elsewhere in the body (systemic), and those effects can be immediate or delayed.
Nonspecific - some toxics are nonspecific and cause damage on contact, wherever that contact is. Acids are a good example of this. However nonspecifics may also move and have effects throughout the body.
Specific chemicals attack only certain organs or systems. Each organ and organ system has different functions and characteristics, therefore the effects of a toxic substance on each system will need to be evaluated separately.
Immediate effects can occur at the site of contact or elsewhere on the body. They may be reversible or subside after the exposure stops, but others do not go away.
Delayed effects may take months or years to appear and can result from either acute or chronic exposure. This lag time between exposure and the display/discovery of effects is called the latency period. Delayed effects may be temporary or permanent.
Exposure Medium is the term for the method of "delivery" of the chemical to the body. The amount of a substance in the air we breathe, the water we drink, or the food we eat is called a concentration. The standard reporting format is in parts per million (ppm), milligrams per liter (mpl) and milligrams per cubic meter (mpcm). The concentration helps calculate the dose.
Hazardous - Some chemicals are hazardous because of their physical properties. They may explode or burn easily, or react violently when exposed to certain other chemicals. A chemical may be toxic, hazardous, or both.
Routes of Exposure: A chemical can cause health problems after it contacts or enters the body. Some chemicals are more or less toxic, depending on the route of exposure. For example, touching lead will not harm the body because it is not absorbed by the skin; however breathing or swallowing lead dust is harmful.
There are three (3) primary routes of exposure:
Inhalation or breathing of gases, vapors, dusts, or mist is very common. Chemicals can enter and irritate the nose, air passages, and lungs. They may be deposited in the airways or absorbed into the bloodstream by the lungs. Blood circulation can then carry chemicals throughout the body.
Ingestion refers to chemicals that get in or on food, utensils, or anything that can be placed in the mouth or swallowed. Once swallowed, some chemicals may be absorbed into the bloodstream and carried throughout the body.
Direct contact with substances that touch the skin or eyes result in absorption into the bloodstream. Damaged skin can allow chemicals to enter the body more easily or infections to occur.
Sensitivity to chemicals: Not all persons are equally sensitive to chemicals and therefore they may not be similarly affected. Some factors that affect sensitivity include: genetic make-up, allergies, age, illness or health, diet, alcohol use, pregnancy, and drug use.
Toxic Substances can be poisonous or impair health. Any chemical, including common household products, can be toxic or harmful under certain conditions. People are generally concerned about chemicals like polychlorinated biphenyls (PCBs) and dioxin which can be found at some hazardous waste sites. Products that we use daily, such as household cleaners, prescription and over-the-counter drugs, gasoline, alcohol, pesticides, fuel oil and cosmetics, can also be toxic.
Toxicity of a chemical: Toxicity is measured by the effect it produces and its potency, or strength. One chemical may have no noticeable effects during exposure, but cause cancer years later; another may cause vomiting upon exposure, but have no known long-term effects. The more potent a chemical is, the more toxic. If smaller amounts of Chemical A can cause greater effects than larger amounts of Chemical C, Chemical A would be considered more toxic. Potency, and therefore toxicity, can be affected by the chemical's breakdown once it is in the body. The body can metabolize (or change) the chemical into another chemical/s that may have more or less toxicity than the original chemical.
"Hurricane Katrina Sludge"
"The Hurricane Katrina tidal surge and flood waters entered New Orleans through breaches in flood walls and levees and transported the contaminated sediment onto the land surfaces, streets, yards, parks, and to the inside of homes, schools, churches, and businesses.
"The contaminated sediment sludge originated in the bottom of water bodies in the path of the hurricane; these included lakes, rivers, and estuaries that had been contaminated by many decades of discharge from industry, business, municipalities, and agricultural runoff.
"The contaminated sediments contained elevated levels of toxic heavy metals arsenic, lead, mercury, cadmium and chromium, polynuclear aromatic hydrocarbons such as Benao(a) pyrene, and a host of gram positive and gram negative micro-organisms.
"Contact with the contaminated sediment sludge layered on surfaces resulted in health impacts such as respiratory illnesses, asthma, allergic reactions, skin rashes, and skin infections that did not respond to normal antibiotic treatments.
"More than two years after the landfall of Hurricane Katrina, the health impacts are still being experienced by people that come in contact with the sediment sludge."
Wilma Subra, m.S. in Microbiology/chemistry; President of Subra Company