Methods of determining toxicity and pollution prevention Toxicity is defined as a measure of how harmful any synthetic or natural substance is to a living organism. The study of toxicity is known as toxicology. A toxic substance is referred to as a toxin. People who study the effect of toxic substances are toxicologists. Much of their work includes testing the effects of chemicals on both animals and nonanimals in an effort to collect data that can be used to determine what levels of the substance may be harmful to people and the environment. Toxicologists have a systematic method of categorizing materials in terms of their toxicity The following graph depicts the general method by which scientists determine the effects of toxins on a living organism That is, in this method, scientists measure the toxin that is consumed by an individual, and a resulting effects of these toxins on the individual, such as mortality , or amount of or the When enough individuals are tested in this method, the results of these studies are plotted on a graph, which can then inform the level of toxicity for the tested toxic chemical or, in some cases, biological agents. For example, Listeria monocytogenes is a food-borne bacterium that causes listeriosis, a rare infection occurring primarily in infants, the elderly, or anyone with a compromised immune system. Pregnant women are also more likely to contract the disease, passing it on to the fetus, which is then at great risk for stillbirth. Because the symptoms of listeriosis are mild in a pregnant woman, the diagnosis may not be made, and, thus, the risk to the fetus is not assessed accurately The following curve illustrates the results of a hypothetical clinical study on 13 pregnant rats. The curve depicts the estimated proportion of stillbhin this rat population as a function of exposure to colony-forming units (cfu) of the L. monocytogenes bacteria 1,00 Note that the X-axis in this curve is based on a logarithmic (log 10) relationship. To read the graph, locate the proportion of stillbirths on the Y-axis intercept it with the solid blue curve, and then find the corresponding X-axis value. The actual exposure amount is interpreted not as a number but as an exponent of 10 0.75 0.50 For example, locate 0.25 on the Y-axis; this proportion means that 25% of the rats will experience stillbirths. 0.25 Extending this proportion to the blue curve on the graph, the corresponding X-axis value is 6, meaning that the exposure of 106 cfu-and not 6 cfu-will result in 25% stillbirths. 0.00 0 2 3 45 67 89 10 11 12 13 L. monocytogenes (log 10 cfu) According to the results of the study, at what exposure will 75% of the rats experience stillbirth? O 107 O 101 109 True or False: This exposure exceeds LD50 True False To reduce exposure to toxins in the environment, people should be more aware of what types of toxins they are exposed to and then implement ways to either prevent or minimize this exposure The following excerpt is from an article describing toxic chemicals in the work environment. Specifically, the article highlights the dangers of polyfluorinated compounds (PFCs). PFCs have been linked to reproductive, developmental, and immune problems in animals and people. Read the excerpt and answer the question that follows. PFC exposure: Office air exposes workers to potentially toxic chemicals-Boston University study John Goddard, February 2012 TORONTO, Canada-"Offices typically feature carpeting, furniture, and other objects treated with stain-resistant coatings that contain polyfluorinated compounds, or PFCs," says a study published in the current Environmental Science & Technology journal. Office workers putting in long hours were found to have higher levels of PFCS in their blood compared to those spending less time in such a building, the study says. All had closed-air ventilation and doors that were closed at night. Levels of a PFC called fluorotelomer alcohol, or FTOH, proved highest in the air of the new buildings and lowest in the air of the old ones, the study says Reproduced with permission Torstar Syndication Services According to the article, what are some simple ways to decrease office worker exposure to toxic substances? Check all that apply. Eliminate carpeting in the office. Encourage workers to take breaks outside. Open the doors and windows from time to time.