ddt is an insecticide that was used extensively quizlet

DDT can cause damage to the organs through prolonged or repeated exposure. Which answer best describes what can be concluded from the results of this experiment? World War II propaganda poster featuring a soldier applying DDT.t. In which regions would the HbA/HbS genotype be associated with an overall fitness DISADVANTAGE, and why? However, the Stockholm Convention on POPs did not ban its use entirely. In contrast to when I was the crab, if thicker shells evolved here it was just by chance. (Suspension, in contrast to cancellation, is the more severe action taken against pesticide products under the law.) The null hypothesis, which states there is no heterozygote advantage. Q6.6. Being at the top of the food chain, humans ingest DDT from food crops that were sprayed with it in the field. The ______ does most of the focusing of light in the eye. How is it possible that the population evolved toward thicker shells, even though mutations toward thinner and thicker shells are equally likely? If the frequency of HbS is 0.1, then what is the expected frequency of HbA/HbS heterozygotes? Why didn't you see this in your experiment? Consider Seely's study as a whole, assess how well her data provide support for the hypothesis that evolution by natural selection had occurred in flat periwinkles. Q3.19. Are the proportions of snails with different shell thicknesses in the histogram similar to the sample of snails you examined on the previous page? If you need to go back and make any changes, you can always do so by going to our Privacy Policy page. The histograms below show data obtained by a student playing crab in the Darwinian Snails simulation. The publication in 1962 of Rachel Carson's Silent Springstimulated widespread public concern over the dangers of improper pesticide use and the need for better pesticide controls. ddt-is-an-insecticide-that-was-used-extensively-quizlet, ddt is an insecticide that was used extensively quizlet, ddt is an insecticide that was used extensively in the mid-1900s to kill mosquitoes quizlet, https://williamheald226kff.wixsite.com/afpsychevan/post/12858420-live-sound-audio-react-logo-shareae-com-zip, https://rodenbough996.wixsite.com/gravrorubti/post/little-girls-on-the-beach-and-pool-30-073-imgsrc-ru, https://torym8larsh.wixsite.com/imharenzoi/post/winter-boy-2-131-imgsrc-ru, 2023 by LULU. Q5.8. Was her prediction supported by the data? Opponents to DDT, admitting that there may be little evidence of direct harm to man, emphasize other hazards connected with its use. By clicking Accept All Cookies, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Many students predict that once crabs are present, offspring snails will have thicker shells than their parents because this will help protect them. ks xI,jr 3'qulMm84]N>0UbP*''(No3ANN?BxZ@ &PS(-W;(I[jwN L/iUPYvA YBy*]|OBequ+m: 9:W0 . Previous findings showed that daughters of the women who had more DDT in their blood had a much heightened risk for breast cancer and increased prevalence of obesity, while sons had heightened risks for testicular cancer. Under the auspices of the United Nations Environment Programme, countries joined together and negotiated a treaty to enact global bans or restrictions on persistent organic pollutants (POPs), a group that includes DDT. After 1959, DDT usage in the U.S. declined greatly, dropping from a peak of approximately 80 million pounds in that year to just under 12 million pounds in the early 1970s. The reason why DDT was so widely used was because it is effective, relatively inexpensive to manufacture, and lasts a long time in . (National Report on Human Exposure to Environmental Chemicals and Updated Tables). Flat periwinkle shell thickness affects periwinkle survival when crab predators are present. Please email. DDT's insecticidal action was discovered by the Swiss chemist Paul Hermann Mller in 1939. Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website. While it is effective as an insecticide, its potent toxicity isnt limited to insects. Environmental Protection Agency. This observation led her to hypothesize that longer horns offer more protection against predation than do shorter horns. It consisted primarily of DDT application to the interior surfaces of rural homes or entire premises in counties where malaria was reported to have been prevalent in recent years. Q3.25. Elizabeth MacLennan is a fact checker and expert on climate change. There may be evolution of shell thickness, but not through natural selection and not necessarily toward thicker shells. Why are the observed and expected frequencies of heterozygotes more similar to each other in the slightly wet region than they are in very wet region? In the above example, which genotype is represented by q2? There is currently no evidence in humans that DDT causes cancer or reproductive problems; however, workers exposed to large concentrations during application have reported a variety of neurological effects. As a result, today, DDT is classified as a probable human carcinogen by U.S. and international authorities. The chemical does not easily break down and is known by scientists to accumulate in the tissues of animals. Cookies used to track the effectiveness of CDC public health campaigns through clickthrough data. This substance is reasonably anticipated to be a human carcinogen based on evidence of carcinogenicity in experimental animals. It still sees limited were found to be lasting . DDT and DDE are stored in the body's fatty tissues. Traces of DDT have been recovered from dust known to have drifted over 600 miles and in water melted from Antarctic snow. She holds a Bachelor of Science in Microbiology with a minor in Health Management and Policy. Why Wont the EPA? Centers for Disease Control and Prevention. Q6.8. The population should now have only thick-shelled snails. DDTs trade names and identifiers include: Exposure to DDT can cause symptoms such as: DDT is highly toxic, and it may be fatal if inhaled, swallowed, or absorbed through the skin. Cohn said she fears that we wont learn until decades from now about chemicals being used widely today that could be doing irreparable harm to our health. This is a sign that toxic chemicals are a multigenerational issue similar to climate change, she toldSierra. In August 1969, DDT usage was sharply reduced in certain areas of USDA's cooperative Federal-State pest control programs following a review of these programs in relation to environmental contamination. Headache, dizziness, nausea, vomiting, incoordination, tremor, mental confusion, hyperexcitable state. On March 14, 1975, the Administrator denied the State of Louisiana a request for emergency use of 2.25 million pounds of DDT on 450,000 acres of cotton to control the tobacco budworm in 1975. DDT is an insecticide that was used extensively in the mid-20th century to control a variety of pests, including bed bugs. Environmental Health Perspectives, vol. They then pass this mutation to their offspring. Which of the following statements is FALSE? No. formulation and application activities) workers should wear protective clothing (like neoprene gloves and an apron) and a self-contained or supplied-air respirator with a full facepiece and operated in positive-pressure mode. Q2.7. The report was requested by Montrose Chemical Corporation, sole remaining manufacturer of the basic DDT chemical. Still, DDT remains in use in some countries. She returned every week for 12 weeks to measure survival of tagged lizards. In all of these future populations, the cystic fibrosis allele still exists at a low frequency. It is up to individual countries to decide whether or not to use DDT. Since the introduction of DDT for mosquito control in 1946, DDT resistance at various levels has been reported from more than 50 species of anopheline mosquitoes, including many that spread malaria. (Reminder: the calculator generates expected frequencies, not observed frequencies. A population that has no variability in a heritable trait will only evolve if, There are mutations in the genes for that trait. As a result of growing environmental concerns, numerous countries around the world came together as part of the United Nations Environment Programme to restrict the usage of a broad selection of persistent organic pollutants (POPs), a group that includes DDT. 103, no. What is your observed p (frequency of HbA) at 100 generations? According to the Centers for Disease Control, in 2020 an estimated 241 million cases of malaria occurred worldwide and 627,000 people died, mostly children in the African Region. A major difference among finch species is in their beaks: both size and shape vary greatly. Horned lizards use their horns to defend against predatory birds. After Carson's alert to the public concerning the dangers of improper pesticide use and the need for better pesticide controls, it was only natural that DDT, as one of the most widely used pesticides of the time, should come under intensive investigation. "Global Status of DDT and Its Alternatives for Use in Vector Control to Prevent Disease." Some bed bugs were resistant to DDT by the 1940s. Shell thickness did change in some of the trials, but the direction and magnitude of change is not consistent. What is the difference (literally) between your observed and expected frequencies of heterozygotes? who would win in a fight libra or sagittarius; advanced spelling bee words for adults; san antonio spurs coaching staff 2021; The U.S. Department of Agriculture, the federal agency with responsibility for regulating pesticides before the formation of the U.S. Environmental Protection Agency in 1970, began regulatory actions in the late 1950s and 1960s to prohibit many of DDT's uses because of mounting evidence of the pesticide's declining benefits and environmental and toxicological effects. How do you interpret your results for the dry region with no sickle-cell disease? Sign up for email updates on nature, environmental politics, living well, and doing good. On the basis of information acquired during these sessions, the Administrator concluded that the potential for an economic emergency existed in 1974 and that no effective alternative to DDT was available. DDT (Dichloro-diphenyl-trichloroethane), for many years one of the most widely used pesticidal chemicals in the United States, was first synthesized in 1874. It was initially used with great effect to combat malaria, typhus, and the other insect-borne human diseases among both military and civilian populations. While initially DDT was an incredibly effective insecticide, its widespread use quickly led to the development of resistance by many insect pest species. Cookies used to enable you to share pages and content that you find interesting on CDC.gov through third party social networking and other websites. Suppose the frequency of homozygous HbA/HbA individuals is 0.01 and the frequency of heterozygous HbA/HbS individuals is 0.18. It is not intended as a substitute for professional advice of any kind. A similar application was approved on February 22, 1974, for use of DDT during the 1974 growing season. Also known as dichloro-diphenyl-trichloroethane, it is one of the most effective yet controversial synthetic insecticides ever developed. A small portion of the population had measurable DDT. While it is effective as an insecticide, its potent toxicity isn't limited to insects. Because genetic drift causes random fluctuations of allele frequencies in populations. ddt is an insecticide that was used extensively. Someone has handed you the following graph of changes in the frequency of one allele in a population over time. Q6.9. Bruce Blumberg, professor of cell and developmental biology at the University of California, Irvine, said the story of DDT underscores the failure of companies and regulators to protect public health from the dangers of many chemicals. DDT is an insecticide that was used extensively in the mid-1900s to kill mosquitoes. The alternative hypothesis is supported: There is evidence for a heterozygote advantage. Q3.14. Yes, the population will evolve toward thicker shells, because the snails need protection against predatory crabs. There is no genetic drift. You will be subject to the destination website's privacy policy when you follow the link. In the body, DDT is converted into several breakdown products called metabolites, including the metabolite dichlorodiphenyldichloroethene (DDE). DDT (Dichloro-diphenyl-trichloroethane), for many years one of the most widely used pesticidal chemicals in the United States, was first synthesized in 1874. Yes, some individuals with certain traits are more likely to survive and pass those traits on to their offspring. Consider the following hypothetical scenario: An ancestral species of duck had a varied diet that included aquatic plants and terrestrial plants and insects. %PDF-1.3 DDT has humble origins for a chemical that would eventually reach much of the world. Exposure to DDT did not end when the chemical was banned in the United States almost 40 years ago. Perform the metric conversion: 10 mL = ___________ L. You have been posted to a remote region of space to monitor traffic. USDA - Fire ant queen with Metarhizium anisopliae fungus Bt - common product among organic gardeners to control lepidopteran pests. DDT cant be dissolved in water, but it is easily dissolved in organic solvents, fats, or oils. Fogging DDT to fight malaria, encephalitis, dengue, and zika in Balik Pulau, Penang. known to be very persistent in the environment. Fry, D. M. "Reproductive Effects in Birds Exposed to Pesticides and Industrial Chemicals." What happens to the frequency of the HbS allele? Allele frequencies remain constant from one generation to the next. what is an aquitard quizlet; ketones normal range urine; scala ordering vs ordered; 2-methylpropanal structure; who is the payee in child support. DDT is one of the most controversial chemical compounds in recent history. First discovered in 1873 by a German chemistry student named Othmar Zeidler, the compound did not receive serious attention until a 37-year-old chemist named Paul Herman Muller synthesized it again in 1936. The Convention includes a limited exemption for the use of DDT to control mosquitoes that transmit the microbe that causes malaria - a disease that still kills millions of people worldwide. The Administrator based his decision on findings of persistence, transport, biomagnification, toxicological effects and on the absence of benefits of DDT in relation to the availability of effective and less environmentally harmful substitutes. bvzm8>OIGbBrbe2?p-~CyPk*B=8k:px\2[)s(BR.FWn$40!W[7QVs:?SuNqZwgD[E-jt8Z,=e Mv-.Qs c Varying restrictions were placed on DDT in different States. Evaluate her hypothesis based on the results shown in both graphs above. w/T,8-iP*=# `VL\|bn /fJ;(c2o!1#zdrp%C; OnT (Zh^M Which of the following would be sufficient for the Hardy-Weinberg equation to accurately predict genotype frequencies from allele frequencies? Based on your data and on what you know about the simulated populations, which allele is more likely to become fixed in the small population? q=+100.kJ,w=65kJ. As part of the testing, a 4-mile area was blanketed with the DDT fog. In 1972, EPA issued a cancellation order for DDT based on its adverse environmental effects, such as those to wildlife, as well as its potential human health risks. DDT (dichloro-diphenyl-trichloroethane) was developed as the first of the modern synthetic insecticides in the 1940s. The HbS allele is more likely to persist in wetter regions because the relative fitness of HbA/HbS heterozygotes is higher where there is more malaria. Some countries outside the United States still use DDT to control of mosquitoes that spread malaria. AFTER malaria is cured, the frequency of the HbS allele should decrease in regions with lots of mosquitoes because: Having one copy of the HbS allele will no longer be advantageous in these regions. DDT was so widely used because it was effective, relatively inexpensive to manufacture, and lasted a long time in the environment. (Hint: What is the genotype of people with sickle-cell disease, and how is that genotype represented in the Hardy-Weinberg equation?). % Which snail population has the larger range of variation in shell thickness? DDT was widely used during World War II to protect soldiers and civilians from malaria, typhus, and other diseases spread by insects. All trademarks, registered trademarks and servicemarks mentioned on this site are the property of their respective owners. In August 1971, upon the request of 31 DDT formulators, a hearing began on the cancellation of all remaining Federally registered uses of products containing DDT. DDT is a possible human carcinogen according to U.S. and International authorities. Since it can dissolve in fats, DDT can build up in the fatty tissues of animals exposed to it. Polukranos, Unchained Deathtouch, Okc Thunder Draft Picks 2020, Ddt Is An Insecticide That Was Used Extensively Quizlet, Part 21 Companies Act 2006, . Keeping the crab happy, the student ate 15 snails twice, letting the population reproduce after each feeding bout. Chlorinated hydrocarbons The chlorinated hydrocarbons were developed beginning in the 1940s after the discovery (1939) of the insecticidal properties of DDT. 19, no. A panel of scientists recommended today that the spraying of DDT in malaria-plagued Africa and Asia . The EPA banned DDT in 1972 after an accumulation of research showing harmful impacts to wildlife and potential human health risks, and its now classified as a probable human carcinogen. After the use of DDT was discontinued in the United States, its concentration in the environment and animals has decreased, but because of its persistence, residues of concern from historical use still remain. 'r.TmzI4 These amendments provide EPA with more effective pesticide regulation mechanisms than were previously available under the FIFRA. According to the EPA, DDT can cause liver damage including liver cancer, nervous system damage, birth defects, and other reproductive harm. It was very effective at first, but after a few decades DDT became less effective at killing mosquitoes because many populations had evolved resistance to DDT. In her book, Carson detailed how a single drop of DDT applied to crops lingered for weeks and months, even after a rainfall. A few mosquitoes in the population were resistant to DDT before it was ever used. Use the following passage to answer the next two questions. Biomonitoring data also help scientists plan and conduct research on exposure and health effects. After reconsideration of the March order, in light of a scientific advisory committee report, the Administrator later reaffirmed his refusal to suspend the DDT registrations. Why didn't this happen in your experiment? The chemical is still used in some places, particularly as an indoor pesticide for mosquitoes in areas where malaria remains a major public health concern. Today, nearly 40 years after DDT was banned in the U.S., we continue to live with its long-lasting effects: products. A famous example of biomagnification is with the pesticide known as DDT. This treaty is known as the Stockholm Convention on POPs, which only allowed use of DDT for controlling malaria. ), Q3.16. Q1.8. Shortly thereafter, particularly during World War II, the U.S. began producing large quantities of DDT for control of vector-borne diseases such as typhus and malaria abroad. Although warnings against such hazards were voiced by scientists as early as the mid-1940s, it was the publication of Rachel Carson's book Silent Spring in 1962 that stimulated widespread public concern over use of the chemical. What is your observed HbA frequency at generation 100? Q1.4. It was very effective at first, but after a few decades DDT became less effective at killing mosquitoes because many populations had evolved resistance to DDT. Of the quantity of the pesticide used in 1970-72, over 80 percent was applied to cotton crops, with the remainder being used predominantly on peanut and soybean crops. These cookies perform functions like remembering presentation options or choices and, in some cases, delivery of web content that based on self-identified area of interests. Saving Lives, Protecting People, https://www.epa.gov/ingredients-used-pesticide-products/ddt-brief-history-and-status, Centers for Disease Control and Prevention, Section 2: Biomonitoring helps to shape policies that affect our health, Section 3: Biomonitoring teaches us about nutrition, Section 4: Biomonitoring helps us respond to health emergencies, Section 5: Learn more about biomonitoring, Dioxins, Furans and Dioxin-Like Polychlorinated Biphenyls, NNAL (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol), Organophosphorus Insecticides: Dialkyl Phosphate Metabolites, Per- and Polyfluorinated Substances (PFAS), Polybrominated Diphenyl Ethers (PBDEs) and Polybrominated Biphenyls (PBBs), U.S. Department of Health & Human Services. EPA History: DDT (dichloro-diphenyl-trichloroethane). Which shell thickness are the most common? As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time? This treaty is known as the Stockholm Convention on POPs. Q1.3. On December 13, 1973, the Court ruled that there was "substantial evidence" in the record to support the EPA Administrator's ban on DDT. Crab predation does not result in differential survival, because compared to thin-shelled snails, thick-shelled snails are more likely to survive in the presence of crabs. If the frequency of HbA homozygotes is 0.1, what is the value of p2? Blood serum levels of DDT and DDE in the U.S. population appear to be five to ten times lower than levels found in smaller studies from the 1970s. DDT was used extensively during World War II by the Allies to control the insect vectors of typhusnearly eliminating the disease in many parts of Europe. Her most recent book is Whitewash: The Story of a Weed Killer, Cancer, and the Corruption of Science. Theresearch, which was published April 14 intheCancer Epidemiology, Biomarkers & PreventionJournal, is the latest in a series of findings generated from a relatively unique study that began in the 1960s, when DDT was widely used. After decades of use, evidence of the pesticide's declining benefits and suspected environmental and toxicological effects were becoming causes for concern. Effects of contact with DDT or inhalation may be delayed. Proudly created withWix.com, Ddt-is-an-insecticide-that-was-used-extensively-quizlet. 110, no. Now that you've seen the results of one trial, how do you think the distribution of shell thickness will change over time in future trials without differential survival? It is asynthetic chemical compound that doesnt occur in nature. What is the difference (literally) between your observed and expected frequencies of heterozygotes? Biomonitoring studies of serum DDT and DDE provide physicians and public health officials with reference values. If the proportion of sickle-cell sufferers (HbS-HbS homozygotes) in a population is 0.16, according to the Hardy-Weinberg equation, what is the proportion of sickle-cell carriers (HbA-HbS heterozygotes) in that population? They help us to know which pages are the most and least popular and see how visitors move around the site. also known as dichloro-diphenyl-trichloroethane, used to control insect vectors of disease, DDT in mothers linked to developmental delays in children, UC Berkeley study finds (press release), DDT still poisons people and wildlife in Michigan 40 years after being banned, DDT compounds found at deadly levels in Michigan birds and eggs, Study shows DDT to be toxic to nervous systems of babies, Monsantos DDT pesticide could raise breast cancer risk by 370%, Glucophage uses, health risks, and side effects at NaturalPedia.com, Norvasc uses, health risks, and side effects at NaturalPedia.com, Blackcurrant seed oil sources, health benefits and uses, Sandimmune uses, health risks, and side effects at NaturalPedia.com. http://www.naturalpedia.com/ddt-toxicity-side-effects-diseases-and-environmental-impacts.html. Could individuals of a species look different today than individuals of the same species did many generations ago? In the early 1950s, due to its success in decreasing mosquito populations, the World Health Organization launched the Global Malaria Eradication Program. Which of the following histograms show the correct representation of the snail shell thickness data 4, 7, 2, 5, 4, 3? DDT is still used today in South America, Africa, and Asia for this purpose. Flat periwinkle shell thickness is variable Even though thicker-shelled snails were less likely to be eaten by carbs, their offspring had random shell thicknesses, so the population can't evolve. DDT was also used in buildings for pest control. The hypothesis that longer horns offer greater protection against predation is NOT supported. Which statements below are TRUE when a gene is at Hardy-Weinberg equilibrium? Which of the following is REQUIRED for the process of evolution by natural selection to occur? Although the remaining States have provisions for the "restricted use" classification of pesticides, no specific mention is made of DDT. Because the crabs preferred thinner-shelled snails, only thicker-shelled snails survived to reproduce. Fungal insecticides - used as pesticides since the late 1800's. Needs humidity and a certain temperature to germinate. 3. Beginning in 1967, the Environmental Defense Fund, the National Audubon Society, the National Wildlife Federation, the Izaak Walton League and other environmental groups became increasingly active in initiating court proceedings leading to the restriction of DDT use at both local and Federal levels. As many years went by, the environment changed such that the aquatic food sources were much more plentiful than those on land. Cystic fibrosis deaths should be more common in regions with tuberculosis. International Programme on Chemical Safety. Q1.14. Now that you've seen two different examples of reproduction with mutation, do you think that the pattern of mutations is random, or directional? For your data from the Very Wet region, what is HbS persistence? For insect-eating birds, this poses a significant problem. Journal of Military and Veteran Health, vol. Considering the above example, if there were 20 offspring in the next generation instead of only 1 or 2, the probability of losing the HbS allele would be Lower, because with more offspring, there is a greater chance that at least one HbS allele will end up in an offspring. 0|9|zG> D@2|/AA>6bcY/4v$$u>[s*k+T.7&rNq `m9(St;_;WJMz+;']oohjx2)|5[|:.^GA+k|)udg(Kqls )>-Gl}#m1[l1d=)$)vQZ!ml ^@N~$/]P>t]o%4X%8:c\}~%98Myr p\&=^uouQq^nu^ft)>"Dqq#/c pc19~ 2022-06-30; wreck on 1942 crosby, tx today DDT got into the . A researcher observed that lizards living in areas with predatory birds have longer horns than those in areas with no predatory birds. Many students predict that the snail shell thickness would still evolve even without variation because the snails need protection against predatory crabs. What Are Persistent Organic Pollutants (POPs)? Q2.3. 1940s DDT was used as the first modern synthetic insecticide to control insect in agriculture, housing, institutes and to combat . Cost, ease of use, species of mosquito, and chemical resistance all play a part in a countrys decision on which insecticide to choose, however, the final factor is whether or not the chosen product works to reduce disease. DDT (dichloro-diphenyl-trichloroethane) was introduced in the 1940s as a highly effective insecticide designed to combat the spread of malaria, typhus, and other diseases carried by insects. Q2.6. Since then, studies have continued, and a relationship between DDT exposure and reproductive effects in humans is suspected, based on studies in animals. 7, 1995, pp. Because of the decision not to suspend, companies were able to continue marketing their products in interstate commerce pending the final resolution of the administrative cancellation process. Which snail population has the larger average shell thickness? This regulatory measure, as well as others which followed, was reaffirmed and extended in June 1970, when the Secretary issued an order banning use of 16 types of pesticides, including DDT, on any lands or in any programs managed by the Department's bureaus and agencies. Many other chemicals are now known to be EDCs, and both Cohn and Brody said we could head off many health problems by curtailing use. The bodys fatty tissues store DDT and DDE. The relative fitness advantage to being heterozygous depends on the chance of being exposed to malaria. A .gov website belongs to an official government organization in the United States. Assume that a population of one of these finch species is undergoing evolution by natural selection with respect to beak size and shape. Also known as dichloro-diphenyl-trichloroethane, it is one of the most effective yet . In regions where malaria does not occur, individuals who are heterozygous HbA/HbS have a fitness advantage over those who are homozygous for the normal hemoglobin allele (HbA). Most villagers have neither disease because they have the HbA/HbS genotype. Is there any variation in shell thickness among the snails now? However, its use has declined due to its persistence in the environment and potential for causing health problems. DDT is an insecticide that was used extensively in the mid-1900s to kill mosquitoes. Both the pros and cons of DDT use were considered by four Government committees who issued the following reports: (1) may 1963, "Use of Pesticides," A Report of the President's Science Advisory Committee (PSAC); (2) November 1965, "Restoring the Quality of Our Environment," A Report of the Environmental Protection Panel, PSAC; (3) May 1969, Report of the Committee on Persistent Pesticides, Division of Biology and Agriculture, National Research Council, to the Agriculture Department; (4) December 1969, Mrak Commission Report.