Toxicity is complex with many influencing factors; dosage is the most important. Xenobiotics cause many types of toxicity by a variety of mechanisms. Some chemicals are themselves toxic. Others must be metabolized (chemically changed within the body) before they cause toxicity.
Many xenobiotics distribute in the body and often affect only specific target organs. others, however, can damage any cell or tissue that they contact. The target organs that are affected may vary depending on dosage and route of exposure. For example, the target for a chemical after acute exposure may be the nervous system, but after chronic exposure the liver.
Toxicity can result from adverse cellular, biochemical or macromolecular changes.
Examples are:
- cell replacement - fibrosis
- damage to an enzyme system
- disruption of protein synthesis
- production of reactive chemicals in cells
- DNA damage
Building materials
Exposure to building materials, products used for home
improvement, and textiles can cause health problems. For example,
particleboard, insulation, carpet adhesives, and other household products emit
formaldehyde, which can cause nausea, respiratory problems, dry or inflamed
skin, and eye irritation. Newly built homes and the confined spaces of mobile
homes can be a particular problem. Using environmentally safe products-such as
paint that contains a low level of or no
volatile organic compounds (VOCs)-can reduce the
chemical load on your body.
Sick building syndrome and building-related asthma
Experts coined the term "sick building syndrome" to
describe acute symptoms that occur only during time spent in a particular
building and that cannot be explained by any specific illness or cause.
Symptoms include headache, dry cough, dry or itchy skin, dizziness, nausea,
difficulty concentrating, fatigue, sensitivity to odors, and irritation of the
eyes, nose, or throat. Typically the symptoms improve after you leave the
building.
Poor ventilation that restricts fresh air flow inside
can be a cause of sick building syndrome. Carpet, adhesives, upholstery,
manufactured wood, pesticides, and cleaning fluids can give off
volatile organic compounds (VOCs), including
formaldehyde. High concentrations of VOCs can cause cancer. Unvented gas and
kerosene space heaters, woodstoves, fireplaces, and gas stoves can produce
carbon monoxide and nitrogen dioxide.
Outdoor sources of
chemicals can also cause sick building syndrome. Pollutants from cars and
trucks and exhaust from plumbing vents and building machinery can enter a
building through vents.
Building-related asthma is
the term used when symptoms of a diagnosed illness can be linked directly to
airborne contaminants within a building. Symptoms include cough, chest
tightness, and wheezing. Leaving the building may not immediately improve the
symptoms.
Bacteria, molds, viruses, and other biological contaminants
Bacteria and molds can breed in stagnant water that builds up in humidifiers, drain pans, and ducts, or where water collects on carpet, ceiling tiles, and insulation. Humidifier fever is an illness caused by toxins from microorganisms that grow not only in large heating and cooling systems in buildings but also in home systems and humidifiers. Legionella pneumophila is an indoor bacterium that can cause Legionnaires' disease.
Some viruses can survive on household surfaces, such as counters or floors, or they can get spread through the air when an infected person sneezes or coughs. You can help control viruses by:
- Cleaning household surfaces with a disinfectant.
- Having adequate ventilation in your house.
- Having anyone with a viral infection, such as a cold or the flu, cough or sneeze into the bend of the elbow or into a tissue.
references:
http://aquaticpath.umd.edu/appliedtox/module1-factors.html
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