Blueprint MCAT Full-Length 1: CARS Passage 8 – Lead Toxicity


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Session 206

Today, we’re investigating lead and its impact on public health in CARS practice passage 8 from Blueprint MCAT’s full-length 1.

We’re joined by Armin from Blueprint MCAT, formerly Next Step Test Prep. If you would like to follow along on YouTube, go to premed.tv.

Get your FREE copy of Blueprint MCAT’s Full-Length 1 to follow along: Go to http://medicalschoolhq.net/blueprint. In the menu, click “MCAT,” then “Free Resources.” (That’s an affiliate link, so if you end up making a purchase from Blueprint later on, I get a small commission at no extra cost to you.)

Listen to this podcast episode with the player above, or keep reading for the highlights and takeaway points.

[02:14] Passage Overview

The first paragraph kind of makes you think about 2020. And the idea is to keep your opinions out of it. There are a lot of different perspectives and you want to stay engaged. So definitely be asking yourself questions while you’re reading this passage, but keep your opinions out of it. Just make sure you follow in line with what the author is trying to conclude.

[04:18] Passage 8 (Questions 42 – 47)

Paragraph 1

Public health has classically been associated with sanitation and the spread of communicable disease. Near the turn of the twentieth century, it also focused much of its efforts on lifestyle factors that were associated with disease and disability (e.g. diet, smoking, exercise). Yet despite this, many of the largest impacts of public health have been related to physical and industrial factors. One of the most potent such examples is the presence of lead as an additive in gasoline in the form of tetraethyllead (TEL), used to increase both fuel economy and vehicle performance. While ethanol was already known to have similar effects, be relatively inexpensive, and have low toxicity, TEL was widely promoted beginning in the 1920s, as it was especially profitable for patent holders.

Note: Keep your opinions out of it. But we’re talking about public health. You can already tell the author has some type of negative bias going into this paragraph about TEL. So once you read a paragraph, ask yourself, what was the main idea? And then what can you highlight in the first paragraph that truly identifies and sums up the main idea?

“We don't really want to take notes on the CARS section unless it's a very difficult passage. We want to use the highlighting technique to somewhat create our own mental map.”Click To Tweet

[08:10] Paragraph 2

Lead, even at very low levels that had previously been considered safe, is toxic to many organ systems in the body. Given TEL’s ability to cross both the placenta and the blood-brain barrier, it is especially damaging to the developing fetus and to young children. Lead exposure at almost any level to the developing fetus can result in diminished intelligence and disruption of later behaviors. With the brain’s low-to-nonexistent regenerative capacity, these deficits are lifelong.

Note: The main idea here is that lead is bad. You could highlight stuff here like “toxic to many organ systems.” The author goes and tells us a mechanism of why it’s specifically toxic to these organ systems. It crosses the placenta and the blood-brain barrier. And it can result in this diminished intelligence and disruption of later behaviors for the developing fetus. So that would be pretty much the the the main idea of this second paragraph.

[09:42] Paragraph 3

As it was known as far back as the nineteenth century that lead was a dangerous substance, and as the very first factory producing TEL killed 17 workers due to massive neurotoxicity almost immediately after it began operating, it seems somewhat surprising that lead was ever permitted to enter widespread use as a fuel additive. In a story that has been repeated over and over again, it was a massive lobbying effort by the lead industry, along with decades of funding junk science, that convinced legislators and the public to accept that leaded gasoline was safe. It wasn’t until 1976 that the US government even began to suggest phasing out TEL in gasoline. After a decade of lawsuits in which various industries sought to block the provisions of the Clean Air Act, the government was able to force industries to phase out leaded gasoline.

Note: The main point here is that we knew lead was dangerous, and yet, we still pushed it. It’s tying back to that first paragraph where we pointed out the “especially profitable for patent holders.” You can highlight “it was known as far back as the nineteenth century that lead was a dangerous substance.” And they continued that because of this massive lobbying effort by the lead industry.

[12:00] Paragraph 4

In one of the more remarkable cases of the government’s ability to rein in industry’s misdeeds, the phase-out of leaded gasoline coincided with an 80% decrease in the blood lead levels of children from 1976 to 1992, which also correlated with a six-point gain in the average IQ score, according to Dr. Landrigan’s research. This improvement cannot all be attributed to unleaded gasoline, of course. For much of the early and mid-twentieth century, lead was found in any number of products, including paint, solder used in plumbing systems, and various types of plastics. The lead phase-out in these products coincided with the reduction of TEL as a gasoline additive, so Dr. Landrigan’s six IQ points may well be attributable to a drop in lead levels in our blood from all sources, rather than just gasoline.

Note: So here’s the author refuting that earlier statement saying that it wasn’t just the lead that decreased the removal of lead from the gasoline that led to the six-point gain in average IQ score for children. It could have actually been attributed that we were at the same time removing lead from many different sources. And the author goes by and gives evidence for paint, solder, and plumbing systems. The idea of this paragraph is to show that removing lead is correlated with some good improvements in blood levels and IQ scores.

[15:40] Paragraph 5

The dominance of the car culture in the US makes it unsurprising that improvements to automotive safety has a major positive impact on the death and disability rates in the country. While fuel makers were being pushed to eliminate lead additives, car manufacturers were facing legislators who began requiring the installation and then use of seatbelts. Studies done by the US National Highway Traffic Safety Administration (NHTSA) suggest that a typical lap-and-shoulder seatbelt reduces the risk of death by almost 50% in crashes of all types. Beginning with New York in 1984, all US states (with the exception of New Hampshire) have passed laws requiring drivers to wear seatbelts while driving. In just the decade from 1991 to 2001, NHTSA data reflects that over 100,000 lives have been saved due to seatbelt use.

Note: Now, we’re talking about automotive safety, specifically about seat belts. Does this correlate? Well, this could fall under the idea of public health. So this paragraph talks about public health measures specifically around the automotive industry that has saved lives.

So at the end of the passage, we were able to read a paragraph and see how the next paragraph fit into the previous paragraphs. And this last paragraph, while it was different from lead, it focused more on automotive safety and also the public health.

[18:27] The Main Idea of the Passage

The main point is to highlight public health measures and their impact on our community and our country. Public health is being focused on these bigger industrial factors and more. Once we read a passage, we reflect back on the main idea, and we’re ready to go into the questions.

“When you read a question, stop. Reword it, and then try to solve it on our own.”Click To Tweet

[19:50] Question 42

The author’s attitude towards the lead industry’s efforts to get TEL included as a gasoline additive can best be described as:

Answer choices:

  1. unsurprised that an industry would risk people’s health for the sake of profit.
  2. horrified that any company or group of companies would risk people’s health for the sake of profit.
  3. regretful that the author personally profited from the inclusion of TEL as a gasoline additive.
  4. angry that scientists were willing to take money from the lead industry to publish junk science that “proved” that TEL was safe as a gasoline additive.

Reworded question: What does the author think about the shady business of corporate lobbying?

Prediction: Going back to the passage, Paragraph 3 talks about lobbying. The author thinks it’s ridiculous.

Then if we look back at the beginning of the paragraph, the author mentions the TEL factory killing 17 workers due to massive narrow toxicity. The author is tired of this happening.

Thought Process:

Remember, we’re sick and tired of this repeating over and over again. This is nothing new. So here, the author’s attitude is definitely unsurprised.

Correct Answer: A

[26:27] Question 43

The passage implies that which of the following facts demonstrates an unqualified success for public health in America?

  1. Every state has passed laws requiring drivers to wear seatbelts while driving.
  2. Ethanol is now commonly used as a gasoline additive.
  3. Government agencies such as NHTSA are empowered to investigate and punish those failing to meet public health standards.
  4. Reduction in blood lead levels due to removal of lead from products has led to an IQ increase.

Reworded question: What is an example of public health success?

Prediction: Removing lead and the use of seat belts required in almost all states

Thought Process:

The answer is D because it matched one of our predictions that removing lead from products led to an increase in IQ levels.

Correct Answer: D

[30:01] Question 44

Which of the following chemicals, if toxic, would be most harmful, given the information in the passage?

  1. Chemical Q, a grey liquid, which can easily pass through biological membranes and organs and is rapidly absorbed by the skin
  2. Chemical X, which is impermeable to biological membranes, is a gas in its usual form, and, when inhaled, can damage the lungs
  3. Chemical T, a contaminant often found in food, which has been known to weaken bones in the elderly, making them more likely to be injured in a car crash
  4. Chemical Z, a byproduct of plastic manufacturing, which damages the liver but is unable to penetrate into nerve tissue or the brain

Reworded question: What do you think the author believes is toxic?

Prediction: In paragraph 2, the author talked about the effects of lead toxicity to many organs crossing the placenta and the blood-brain barrier damaging the fetus. So we’re going to look for something that has similar properties.

Thought Process:

The answer choice that matched our prediction is A.

Correct Answer: A

[31:39] Question 45

Which of the following, if true, would most weaken one of the arguments presented in the passage?

  1. In the late 1990s, the use of activated charcoal as an effective chelating agent to remove heavy metals from the digestive tract gained widespread popularity.
  2. Beginning in the mid-1970s, the federal government significantly increased investment in public education to improve children’s reading, reasoning, and math skills.
  3. Seatbelt installation had been voluntarily adopted by almost all car manufacturers by the mid-1970s.
  4. In the 1800s, the knowledge that lead was a dangerous substance was limited to a relatively small number of people working in the then-new field of public sanitation.

Note: We cannot predict this one. But be ready to evaluate each answer choice to determine whether it weakens the author’s argument or not.

Thought Process:

Let’s evaluate: 

A – It’s beyond our timeline now because the argument was that lead was being removed and this decrease in blood lead level happens from 76 to 92. And this happened in the late 90s. So It doesn’t really affect the author’s arguments. So we cross this out.

Note: Let’s just reflect back on the author’s arguments. The author’s arguments are: lead is dangerous. There are lobbyists out for profit. We removed lead and we saw improvement in the IQ of individuals. And by requiring drivers to wear seat belts, we have saved many lives. So let’s just keep those in mind as we go on to the next answer choice.

B – One of the arguments is blood levels went down, and it correlated with this increase in IQ. And this potentially says, there’s another reason why IQ went up. And it’s not the lead decrease. Bingo! This could possibly weaken the author’s argument. If you’re running out of time, you can pick this answer choice and move on. But if you still have time, let’s move on.

C – It just talks about seatbelts saving lives. The author is mentioning at the bottom that laws are requiring drivers to wear seatbelts. We could then cross this out.

D – This doesn’t necessarily weaken the author’s argument.

Correct Answer: B

[37:07] Question 46

As the passage describes it, which of the following would most directly fit the “classical” understanding of public health as the field was first developed?

  1. The safety and effectiveness of a vaccine for HPV in preventing not only HPV infection but also the subsequent development of cervical cancer was a primary concern of several physician groups early in the 21st century.
  2. Government officials warned about the risks of cocaine addiction and overuse as a stimulant as early as the 1880s.
  3. Boards of physicians were routinely consulted about the dangers of radiation exposure when nuclear power plants were first being constructed in the mid-twentieth century.
  4. Doctors received professional development training that encouraged them to install and use ergonomically-correct furniture in their own offices to reduce the incidence of repetitive stress injuries at work.

Reworded question: What is going to be considered public health classically?

Prediction: The author mentions that classically public health has been associated with sanitation and the spread of communicable diseases. And then expanded to focus on lifestyle factors. So classically, it’s just been sanitation and the spread of communicable diseases.

Thought Process:

A – Does this mention the spread of communicable diseases? Possibly.

B – It’s not associated with communicable diseases, but lifestyle factors.

C –  Communicable diseases and sanitation? This is more a physical and industrial factor so let’s cross this out.

D – Not related to communicable diseases

So, A is the correct answer.

Correct Answer: A

[40:20] Question 47

Given the views described in the passage, the author would most likely be in favor of which of the following proposals?

  1. A federal administration proposes removing regulations on the grounds that they are burdensome and that those in the industry have the expertise needed to set voluntary guidelines to ensure the safety of the public and their workers.
  2. A country passes a law which creates a universal ban on the use of lead in any product or industrial application at any level, even in cases in which the alternative is a chemical that is potentially more harmful.
  3. A senator puts forth a draft of legislation calling a halt to any new patents being issued until more stringent safety regulations can be put in place, requiring new patent holders to demonstrate that their devices would not harm the public.
  4. A new piece of legislation empowers the relevant federal agencies to requisition funding to investigate potential junk science that is leading to negative impacts on public health.

Reworded question: Based on the author’s arguments, so what else would they argue?

Prediction: The main idea is putting the interest of public health first, and not the interests of corporations. So we’re gonna have that prediction as we go into the answer choices.

Thought Process:

A – This is not what the author or any brilliant person would assume.

B –  The first half of this is okay. And then if the student didn’t read the rest of the, which proves this one wrong, they can get trapped with that one. So we cross out this one because of the last part.

C – Our prediction was that we want to put the public health interests first, over any corporation interest now. C is saying requiring new patent holders to demonstrate that their devices would not harm the public. And it’s any patent holder and it seems extreme. We have to ask ourselves, does the author believe that all new patent holders should be stopped until they prove, or is it just specific patent holders? So we have to keep that in mind that this could be somewhat extreme. So now between C and D, D is the better answer choice.

We can’t assume that the author is tired of capitalism, right? The author is tired with specific areas that capitalism has, you know, empowered or hasn’t really stopped. But in all of capitalism as a whole, we can’t really, you know, make that conclusion.

Specifically, we’re looking for people to act in the best interest of public health. And that’s stopping junk science. Junk science is something that led to TEL being used in gasoline. So if we stop that, legislators would be less likely to be swayed by pseudoscience, and more likely to be swayed by what’s important and what’s beneficial for public health.

Correct Answer: D

[45:58] Final Thoughts

'As you're going throughout the passage, ask yourself these engaging questions to stay engaged.'Click To Tweet

Reading these CARS passages allows you to explore other pathways that you probably wouldn’t have taken on in another universe. So here’s your opportunity. Instead of seeing it as being boring, be interested in it.

Links:

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