USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 351:

  Several groups of organic compounds are associated with serious toxic effects when highly toxic and dangerous as a solvent; used in the manufacture of rubber, dyes, and lubricating oils

  A. nitrosamines

  B. epoxy compounds

  C. PCBs

  D. formaldehydes

  E. organophosphorus compounds

  Correct Answer: A

  Nitrosamines are highly toxic and dangerous to handle when used as solvents. Toxic amounts may be absorbed without warning because danger signals such as specific odor or irritant effects are lacking. The manufacture of rubber, dyes, lubricating oils, explosives, insecticides, and fungicides, as well as the electrical industry, all have associations with these substances. Nitrosamines have animal carcinogenic properties and have been transmitted transplacentally in rats.

• Question 352:

  Several groups of organic compounds are associated with serious toxic effects when used as insecticides and responsible for more deaths on a worldwide basis than any other group of insecticides

  A. nitrosamines

  B. epoxy compounds

  C. PCBs

  D. formaldehydes

  E. organophosphorus compounds

  Correct Answer: E

  Organophosphorus compounds have been widely used since the 1950s as insecticides, both in national pest control programs and domestically. They have been responsible for many deaths on a worldwide basis, despite the lives initially saved by control of mosquitoes and malaria. From the point of view of the environmental toxicologist, it was perhaps fortuitous that many pests began to develop resistance to the substances fairly early in the use of these compounds. More recently, concern for environmental control has further limited their use; studies have attributed carcinogenic properties to several of these pesticides.

• Question 353:

  Several groups of organic compounds are associated with serious toxic effects when used in transformers because they withstand high temperatures

  A. nitrosamines

  B. epoxy compounds

  C. PCBs

  D. formaldehydes

  E. organophosphorus compounds

  Correct Answer: C

  PCBs were extensively used in the manufacture of electrical transformers until production was halted in the mid-1970s. The first sign of chronic exposure to these substances is the appearance of an acne- like eruption with inflammatory pustules. Other effects are eye irritation and GI disturbance. The substances are persistent, and more than 25% of the population in the United States was discovered to have residues of greater than one part per million (ppm) in adipose tissue. Dietary exposure of the general population has been alleged to occur through milk, eggs, cheese, meat, and fish

• Question 354:

  For each organism causing food-related illness, choose the corresponding average incubation period. What is the average incubation period of Salmonella?

  A. under 4 hours

  B. 824 hours

  C. 1236 hours

  D. 12 hours to 6 days

  E. 13 weeks

  Correct Answer: C

  Knowing the incubation period (average and range) of a pathogen can be important in determining the source of infection in food-borne disease. Knowing what food was eaten on the day of an attack of food poisoning may not help in establishing C. botulinum as the cause of illness, since certain strains of S. aureus cause food-borne disease by the production of enterotoxin. As no time is required after ingestion for the growth of colonies in the infected host, and the toxin affects the vagus nerve in the stomach, the incubation period is under 4 hours. C. perfringens, formerly known as Clostridium welchii, causes food-borne disease, after 824 hours when enterotoxin is released when C. perfringens passes from stomach to intestine. Meat prepared in bulk for consumption at a banquet or in an institution is a possible source. Spores that survive incomplete cooking may start reproducing during cooling and may persist if subsequent rewarming is not completed to a temperature above 60°C (140°F) required to kill the organisms. Salmonella has an incubation time of 1236 hours. It may also survive in meat and other products if cooking is inadequate and heat does not penetrate below the surface of the food. The organisms multiply in the gut of the infected host, and low infective doses may therefore have longer incubation periods

• Question 355:

  For each organism causing food-related illness, choose the corresponding average incubation period.

  What is the average incubation period of Staphylococcus aureus:

  A. under 4 hours

  B. 824 hours

  C. 1236 hours

  D. 12 hours to 6 days

  E. 13 weeks

  Correct Answer: A

  Knowing the incubation period (average and range) of a pathogen can be important in determining the source of infection in food-borne disease. Knowing what food was eaten on the day of an attack of food poisoning may not help in establishing C. botulinum as the cause of illness, since certain strains of S. aureus cause food-borne disease by the production of enterotoxin. As no time is required after ingestion for the growth of colonies in the infected host, and the toxin affects the vagus nerve in the stomach, the incubation period is under 4 hours. C. perfringens, formerly known as Clostridium welchii, causes food-borne disease, after 824 hours when enterotoxin is released when C. perfringens passes from stomach to intestine. Meat prepared in bulk for consumption at a banquet or in an institution is a possible source. Spores that survive incomplete cooking may start reproducing during cooling and may persist if subsequent rewarming is not completed to a temperature above 60°C (140°F) required to kill the organisms. Salmonella has an incubation time of 1236 hours. It may also survive in meat and other products if cooking is inadequate and heat does not penetrate below the surface of the food. The organisms multiply in the gut of the infected host, and low infective doses may therefore have longer incubation periods

• Question 356:

  For each organism causing food-related illness, choose the corresponding average incubation period. What is the average incubation period of C. botulinum?

  A. under 4 hours

  B. 824 hours

  C. 1236 hours

  D. 12 hours to 6 days

  E. 13 weeks

  Correct Answer: D

  Knowing the incubation period (average and range) of a pathogen can be important in determining the source of infection in food-borne disease. Knowing what food was eaten on the day of an attack of food poisoning may not help in establishing C. botulinum as the cause of illness, since certain strains of S. aureus cause food-borne disease by the production of enterotoxin. As no time is required after ingestion for the growth of colonies in the infected host, and the toxin affects the vagus nerve in the stomach, the incubation period is under 4 hours. C. perfringens, formerly known as Clostridium welchii, causes food-borne disease, after 824 hours when enterotoxin is released when C. perfringens passes from stomach to intestine. Meat prepared in bulk for consumption at a banquet or in an institution is a possible source. Spores that survive incomplete cooking may start reproducing during cooling and may persist if subsequent rewarming is not completed to a temperature above 60°C (140°F) required to kill the organisms. Salmonella has an incubation time of 1236 hours. It may also survive in meat and other products if cooking is inadequate and heat does not penetrate below the surface of the food. The organisms multiply in the gut of the infected host, and low infective doses may therefore have longer incubation periods

• Question 357:

  For each organism causing food-related illness, choose the corresponding average incubation period.

  What is the average incubation period of Clostridium perfringens?

  A. under 4 hours

  B. 824 hours

  C. 1236 hours

  D. 12 hours to 6 days

  E. 13 weeks

  Correct Answer: B

  Knowing the incubation period (average and range) of a pathogen can be important in determining the source of infection in food-borne disease. Knowing what food was eaten on the day of an attack of food poisoning may not help in establishing C. botulinum as the cause of illness, since certain strains of S. aureus cause food-borne disease by the production of enterotoxin. As no time is required after ingestion for the growth of colonies in the infected host, and the toxin affects the vagus nerve in the stomach, the incubation period is under 4 hours. C. perfringens, formerly known as Clostridium welchii, causes food-borne disease, after 824 hours when enterotoxin is released when C. perfringens passes from stomach to intestine. Meat prepared in bulk for consumption at a banquet or in an institution is a possible source. Spores that survive incomplete cooking may start reproducing during cooling and may persist if subsequent rewarming is not completed to a temperature above 60°C (140°F) required to kill the organisms. Salmonella has an incubation time of 1236 hours. It may also survive in meat and other products if cooking is inadequate and heat does not penetrate below the surface of the food. The organisms multiply in the gut of the infected host, and low infective doses may therefore have longer incubation periods

• Question 358:

  Which of the following institutions is involved in mounting international control programs for the eradication of communicable disease?

  A. Food and Drug Administration (FDA)

  B. United States Department of Agriculture (USDA)

  C. Environmental Protection Agency (EPA)

  D. United Nations Food and Agriculture Organization (FAO)

  E. World Health Organization (WHO)

  Correct Answer: E

  In the United States, the organization of food and water control is complex. Among the federal control agencies, the EPA is the most recent, and in many ways the most active and powerful. This agency has now set up an elaborate system of regulation and control of the use of pesticides (which until 1970 was the responsibility of the USDA) and has banned the marketing of chlorphenothane (DDT) for use in the home. The FDA has authority to remove food from the market if it contains pesticides (e.g., PCBs in fish) in excess of the action levels set by the EPA. The FDA also retains the authority to remove from the market any food with inappropriate additives, that contains substances harmful to human health, that is stored in unsanitary conditions, that has decomposed, or that is not fit for consumption.

  The USDAenforces wholesomeness standards that it sets for the production and sale of meat. International control is assisted by the WHO. This agency has mounted control programs for the eradication of communicable disease with conspicuous success in the case of smallpox. It also publishes the International Statistical Classification of Disease (ICD-9).

• Question 359:

  Which regulatory agency enforces standards in the sale of meat?

  A. Food and Drug Administration (FDA)

  B. United States Department of Agriculture (USDA)

  C. Environmental Protection Agency (EPA)

  D. United Nations Food and Agriculture Organization (FAO)

  E. World Health Organization (WHO)

  Correct Answer: B

  In the United States, the organization of food and water control is complex. Among the federal control agencies, the EPA is the most recent, and in many ways the most active and powerful. This agency has now set up an elaborate system of regulation and control of the use of pesticides (which until 1970 was the responsibility of the USDA) and has banned the marketing of chlorphenothane (DDT) for use in the home. The FDA has authority to remove food from the market if it contains pesticides (e.g., PCBs in fish) in excess of the action levels set by the EPA. The FDA also retains the authority to remove from the market any food with inappropriate additives, that contains substances harmful to human health, that is stored in unsanitary conditions, that has decomposed, or that is not fit for consumption.

  The USDAenforces wholesomeness standards that it sets for the production and sale of meat. International control is assisted by the WHO. This agency has mounted control programs for the eradication of communicable disease with conspicuous success in the case of smallpox. It also publishes the International Statistical Classification of Disease (ICD-9).

• Question 360:

  Catfish caught in a freshwater stream in Florida has been identified as exceeding the action level for polychlorinated biphenyls in fish (PCBs). Which regulatory agency is responsible for defining these action levels?

  A. Food and Drug Administration (FDA)

  B. United States Department of Agriculture (USDA)

  C. Environmental Protection Agency (EPA)

  D. United Nations Food and Agriculture Organization (FAO)

  E. World Health Organization (WHO)

  Correct Answer: C

  In the United States, the organization of food and water control is complex. Among the federal control agencies, the EPA is the most recent, and in many ways the most active and powerful. This agency has now set up an elaborate system of regulation and control of the use of pesticides (which until 1970 was the responsibility of the USDA) and has banned the marketing of chlorphenothane (DDT) for use in the home. The FDA has authority to remove food from the market if it contains pesticides (e.g., PCBs in fish) in excess of the action levels set by the EPA. The FDA also retains the authority to remove from the market any food with inappropriate additives, that contains substances harmful to human health, that is stored in unsanitary conditions, that has decomposed, or that is not fit for consumption.

  The USDAenforces wholesomeness standards that it sets for the production and sale of meat. International control is assisted by the WHO. This agency has mounted control programs for the eradication of communicable disease with conspicuous success in the case of smallpox. It also publishes the International Statistical Classification of Disease (ICD-9).