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Topic 4

Topic 4. Unit 3 – Environmental Chemistry. Pollution and pollutants. A pollutant is any material or energy that can cause harm to a living thing. Pollution is a change to the environment that that produces conditions that harm living things. A pollutant may not always cause pollution.

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Topic 4

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  1. Topic 4 Unit 3 – Environmental Chemistry

  2. Pollution and pollutants • A pollutant is any material or energy that can cause harm to a living thing. • Pollution is a change to the environment that that produces conditions that harm living things. • A pollutant may not always cause pollution.

  3. How much is that? • The amounts of substances are often said as percent's. • Percent by weight is usually found by taking the grams of a chemical divided by the total grams of the substance x 100%. • %weight = 5 g in 100g = 5% by weight • %weight = 5 g in 500g = 1% by weight • It’s like finding your average on a test.

  4. But what if amounts are really small? • If amounts are small, much smaller than 1% we use different units. • We might use parts per million instead of per hundred (ie. Percent) • Or maybe parts per billion or trillion.

  5. Parts per million (ppm) • Used for very low or dilute concentrations • Usually it simplifies to mg/kg = 1 ppm. • If aqueous 1 kg of water = 1L or 1000mL therefore mg/L also = 1 ppm • Eg. If 2.2 mg of dissolved O2 is found in 250mL of water, what is the ppm of oxygen in the water. • Start the question as a ratio, something over something. • Change the units to get mg/kg or mg/L • Concentration = 2.2 mg = 2.2 mg = 8.8 mg = 8.8 ppm 250 mL 0.250L L

  6. The Danger in the Dose • Toxicity is the ability of a chemical to cause harm. • Acute Toxicity has serious symptoms after 1 dose • Chronic Toxicity has symptoms after the chemical accumulates over time.

  7. Lethal Dose 50 (LD50) • LD50 is the dose of a chemical that will kill 50% of the population it’s applied to. • Different chemicals have different LD50s. • The Gov’t has the responsibility of “acceptable risk” for a substance. Small doses may be o.k. • If rats die from a chemical would it still be ok for humans.

  8. What is a toxin? A toxin is a substance that is capable of inducing adverse effects (i.e. illness, organ dysfunction or death) to living organisms

  9. What is risk? Risk is the probability or likelihood that adverse effects will occur when a living organism is exposed to a toxin.

  10. What determines risk? • Response of the host (based on host’s physiology) • Physical properties of the toxin • Dose or concentration of toxin which includes the amount of the substance, duration of exposure and frequency of exposure • Synergistic effects  combination of different elements or materials

  11. What is the relationship between dose and response? The greater the dose of most toxic materials, the greater the response or reaction Response Dose

  12. How is the toxicity of a substance expressed? - The terms LD50 (lethal dose) or LC 50 (lethal concentration) are used to express the toxicity of a substance. The lower the number, the more toxic the substance. - The LD50 or LC50 is determined by the concentration or dose of a material (g/kg) that results in the death of 50% of a sample group of laboratory animals.

  13. Toxicity rating for LD or LC50? Non-toxic: >15 g/kg (> quart) Slightly toxic: 5-15 g/kg (pint to a quart) Moderately toxic: 0.5-5 g/kg (fluid ounce to a pint) Very toxic: 50-500 mg/kg (teaspoon to an ounce) Extremely toxic: 5-50 mg/kg (7 drops to a teaspoon) Super-toxic: <5 mg/kg (<7 drops) From “Occupational Toxicology”, Michael S. Bisesi, Ph.D., R.S., C.I.H., 1992

  14. OSHA definition of toxic and highly toxic material

  15. What is an exposure limit? • An exposure limit is the concentration of a substance to which most individuals may be exposed to repeatedly without adverse effects • Exposure limits are typically expressed in parts per million (ppm) or milligrams per cubic meter (mg/m3)

  16. Who establishes exposure limits? The Occupational Safety and Health Administration (OSHA) establishes permissible exposure limits (PEL), short-term exposure limits (STEL) and Ceiling limits (C) for chemicals in the workplace. These limits can be found in the Code of Federal Regulations Part 1910.1000.

  17. How does exposure occur?

  18. What is the major route of exposure in the laboratory? The most common route of chemical exposure in the laboratory is through inhalation. Inhalation of toxic gases, vapors, mists, particles, fibers or dust can be absorbed through the mucous membranes and can quickly pass into the circulatory system.

  19. What types of responses are there to toxins? • ACUTE vs. CHRONIC • Acute – the response is immediate and typically reversible • Chronic – the response is delayed or accumulative and is typically not reversible

  20. Examples:

  21. Responses: • Local vs. Systemic • Local – the effect occurs at the point of contact • Systemic – Effect occurs away form the point of contact, typically to an organ or organ system

  22. Examples:

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