Fertility

Did Leaded Gasoline Contribute to the U.S. Baby Bust?

Maybe, but it's more likely that Americans chose to have fewer kids.

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LeadedGasolineBronwyn8Dreamstime
Bronwyn8/Dreamstime

The U.S. fertility rate has fallen to a 40-year low of 1.76 children per 100 women, according to the Centers for Disease Control and Prevention (CDC). Is lead to blame?

A new study by three Carnegie Mellon University (CMU) economists says it is. Noting that "increased lead exposure lowers the general fertility rate for women of childbearing age," the trio argues that "reductions in airborne lead between 1978 and 1988 increased fertility rates and that higher lead in topsoil decreased fertility rates in the 2000s." They might be right, but another explanation for the falling fertility rate is more convincing.

Between 1973 and 1996, the U.S. completed the process of totally eliminating lead as an additive in gasoline. As a result, lead concentrations in the atmosphere have dropped by 99 percent since 1980. In their study, the CMU economists look at fertility rate trends in that portion of the population (about 30 percent) where they have adequate data for atmospheric concentrations of lead in the 1980s. They similarly seek to correlate fertility rates in about 70 percent of the population with their exposure to lead in the topsoil after the year 2000.

After taking into account possible confounders—local climate, housing, socioeconomic status, education, nearness to highways, race, poverty, unemployment rates—they calculate that the decline in airborne lead meant 95,000 additional babies would be born annually. They also estimate that cleaning up areas with high concentrations of lead in the topsoil to the median level of contamination would induce an additional 166,000 births annually.

The researchers do find a correlation between seeking out infertility services and living in states with above-average airborne lead concentrations. But CDC data show that the infertility rate for married women fell from 11.2 percent in 1965 to 10.3 percent in 1976 and further to 8.4 percent in 1982, and the use of leaded gasoline was increasing for most of that period. The CDC reports that the infertility rate among married women continued to fall, reaching about 6 percent in 2010, despite the fact that the CMU researchers identify ongoing exposure to lead in topsoil as a contributing factor to lower fertility rates. (I cite infertility rates of married women because that's the longest consistent dataset offered by the CDC.)

Interestingly, data from the 1950s report atmospheric lead concentrations in major cities that were similar to those during the 1980s. Yet post–World War II fertility rates soared, resulting in the baby boom. U.S. total fertility rates fell steeply from the baby boom years, reaching their nadir of 1.74 children per woman in 1976. Total fertility rose to 2.08 children in 1990 and then held more or less steady at around 2 children per woman, rising to a pre–Great Recession peak of 2.12 children in 2007.

The CDC has tracked contraception use among married women from 1965 onwards (adding unmarried later). In 1965, some 63 percent of married women were using some form of contraception, including oral contraceptives, IUDs, and condoms. That rose to nearly 68 percent in 1976, as oral and intrauterine contraceptives displaced condoms. In addition, sterilizations increased from 7.8 to 18.6 percent of women during that decade. In 2008, the CDC reports, 78.6 percent of married women practiced some form of contraception.

Another way to parse U.S. fertility data is to consider just how many children U.S. women on average intended to have versus the actual number that they give birth to. A 2005 study looking at intended and ideal family sizes between 1970 and 2002 finds that both remained stable at just over two children during that period. "Reported fertility intentions of American women approximate the country's contemporary period levels of fertility," notes the study. Adding that their findings show "in the aggregate, both stable intentions across time and an ability to realize those intentions."

A 2010 study that looked at the childbearing intentions of a late baby boom cohort (born between 1957 and 1964) found that the women aimed to give birth to an average of 2.22 children. By 2006, they had given birth to 1.97 children on average. So why did a substantial proportion of Americans in that cohort end up having fewer children than they intended? The researchers highlight the role played by "life-course factors," finding that "both women and men who postponed childbearing or marriage were much more likely to have fewer births than they intended." The study points out that postponement implicates declining fecundity with age, competing nonfamilial activities, and failure to find a suitable marriage partner.

Exposure to lead is undeniably harmful to human health. And perhaps it has contributed to lower U.S. fertility rates. But it seems more likely to me that U.S. fertility rates have fallen largely because Americans are choosing to have fewer children.

For further background, see also my analysis of the claims that exposure to leaded gasoline increased U.S. crime rates.

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  1. Noting that “increased lead exposure lowers the general fertility rate for women of childbearing age,” the trio argues that “reductions in airborne lead between 1978 and 1988 increased fertility rates and that higher lead in topsoil decreased fertility rates in the 2000s.”

    This makes complete sense, assuming that human beings are entirely created by their environments and have no agency whatsoever.

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  2. Fun fact: the guy who invented leaded gasoline also developed some of the first CFCs, and then was strangled to death by a system of pulleys he’d designed to help him get out of bed after he contracted polio.

    1. With a story behind a name like “Thomas Midgley, Jr.” I could see an excellent dark comedy made out of this.

      1. The Coen brothers could do it as sort of an anti-Hudsucker Proxy.

  3. Wasn’t there a theory that the use of leaded utensils and cookware cause the Roman empire to slowly go insane, leading to its downfall? I think there might be something to the lead theory here.

      1. Lead is the only theory that can explain our modern college campuses.

        1. I would be inclined to agree, but the average Millennial hipster Womyn’s Studies major at Oberlin has significantly less lead in their body today than the average randy frat boy at FSU did 30 years ago.

          Unless you are arguing that lead makes you more logical.

    1. As Ron Bailey points out, yes, there is such a theory but no, it does not hold water.

      Lead was in use for hundreds of years before the collapse of the Roman Empire. Lead remained in use during both periods of decline and periods of cultural resurgence. The lead was primarily used in pipes, not cookware. In that environment, lead oxidizes. Unlike iron-oxide (rust), lead oxide actually forms a harder protective layer than the underlying metal. This acts to prevent further oxidation. That means the first users of a lead-based system are exposed to more lead than their successors – the opposite of the pattern that would be necessary for your decline theory to work.

  4. Wow, it’s almost as what people intend to do isn’t the same thing as reality.

  5. They also estimate that cleaning up areas with high concentrations of lead in the topsoil to the median level of contamination would induce an additional 166,000 births annually.

    And there’s the money shot, the phrase that pays. At even a modest few mil per life, that’s half a trillion dollars per annum that can be tossed on to the “benefit” side of the EPA’s cost/benefit analysis of mandating topsoil clean-up of any soil having some arbitrary level of lead in it, undoubtedly some fraction of the naturally occurring lead levels in mountainous areas of the US. And never mind that it’s easy enough to argue that the children who weren’t born were not born in impoverished areas of fly-over country and destined to be a burden on the taxpayer and therefore their not being born is a net benefit. Sure, we may have inadvertently killed the next Einstein or the next Michelangelo – more likely we killed the next John Wayne Gacy or the next Adam Sandler.

  6. HUD should make low income housing out of lead.

    1. And instead of a work requirement for public assistance there should a contraception requirement, right?

      1. I think the U.S. already tried this, actually. Well, maybe it wasn’t a requirement but the thought went that three generations of imbeciles was enough if memory serves.

  7. So here’s a fun question.

    Assume for a moment that lead concentrations in air/soil/etc.-and-so-on did have an impact on fertility rates, IQ, and so-on.

    What’s the “libertarian” response? This kind of long-term indirect harm/damage is a classic case for regulation and government action, but both are things that are normally anathema to y’all. And it’s not like folks are positioned to individually go after individual polluters. The damage is just too wide-spread and difficult to quantify on a personal basis. So what’s the “libertarian” response? How do folks seek justice, how do folks prevent it from happening again, and how do folks mitigate the on-going effects?

    To be clear, I’m not trying to weigh-in on “did it or didn’t it”, as I think we’re largely past the point where it matters, I’m just curious if y’all have any solutions that stay within the confines of your chosen ideology.

    1. So what’s the “libertarian” response?

      I would think that there would be no response because there’s really no solution currently, even if it were a problem. If there’s some small amount of lead lurking in almost everything, then it sounds like something you can’t fix. The only thing may be to hope for some entrepreneur with an innovative product that somehow removes lead from your home or your land. There are already water filters that remove it from water. Besides, if you live an an older house, you’re surrounded by lead-based paint, which isn’t a problem unless you start to try to remove it.

      Why? What sort of government force do you think would rid the entire environment of trace amounts of lead?

      1. When we talk about direct harms from bad products, the libertarian argument is usually “we don’t need regulation, just let folks harmed by the product sue and companies will self-police to preserve their bottom line”.

        What you are telling me here is that there is no way to incentivize companies to not poison the environment, so long as the effects of the poisoning are not immediately evident.

        Is that correct?

    2. Arguably the response in that scenario would be ‘people wouldn’t buy a product that they know is killing themselves, their children, and causing everyone to die off’.

      But, then again, there are guys like Ehrlich out there who would say ‘good, fewer people is better for everyone’ so…I dunno. The odd’s that such a thing would kill everyone is vanishingly small, so I guess I’ll answer ‘evolution’ to this one.

      Those who are resistant to lead shall inherent to Earth.

      It’s a little sarcastic, but also a little truthful in terms of worst-case-scenario.

      1. Arguably the response in that scenario would be ‘people wouldn’t buy a product that they know is killing themselves, their children, and causing everyone to die off’.
        As the son of a life-long smoker, you seem quite wrong.

        Also I think your aim is off, as we’re talking about slow/indirect effects such that in most cases people won’t know that the product is “killing” them, or may not be customers at all.

        1. And what’s your response to the fact that FDA regulations have resulted in more early deaths than they’ve saved? Enjoy your inconsistency.

    3. What’s the “libertarian” response? This kind of long-term indirect harm/damage is a classic case for regulation and government action, but both are things that are normally anathema to y’all.

      You make the erroneous assumption that only the government can regulate. A libertarian society would likely have many regulations, but they’d be regulations on private property. I would expect that in a libertarian society, many of the private roads and private neighborhoods would simply have banned the use of leaded gasoline.

      In fact, several local jurisdictions banned the use of leaded gasoline when it first appeared (local jurisdictions tend to act more like private HOAs); it was the federal government (in response to lobbying) that made the use of leaded gasoline across the country possible.

      So the libertarian response to this is simple and the same as to many other supposed ills of free markets: you are misattributing the problem. As with slavery and pollution, the government wasn’t the solution to a problem created by free markets, rather the government was the cause of a problem that would never have occurred in a libertarian society in the first place.

  8. I blame Robert Plant.

  9. When I think about things that have impacted U.S. fertility rates over the last 40-50 years, there are one or two social advances that come to mind way before “lead” does.

    1. The Internet, for one.

      1. Planned Parenthood and legal abortion, for another. ^_-

      2. Planned Parenthood and legal abortion, for another. ^_-

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  11. This “study” is the type of ridiculous nonsense you get when economists try their hands at toxicology.

    According to CDC NHANES surveys, US blood lead levels have been steadily declining for the past 50 years; if lead were as critical to fertility as the article implies our fertility rate would be going up, not down.

    Furthermore, airborne lead is far more easily absorbed by the body than soil lead, so comparing the two types of exposure is misleading.

    But then “misleading” describes most environmental research nowadays.

    1. you have a passion for lead, or you’re angry at the economists ?

  12. With all the Monsanto GMO’d corn being made into ethanol and mixed with gasoline spewing into the air from the evil internal combustion engine, expect birthrates to fall even farther as the tainted molecules infect our soil and water.

    dOOm is coming for sure, this time.

  13. From the lede: 1.76 children per 100 women,

    Somehow I doubt the birth rate has fallen that far. Typo?

    1. Freudian slip.

      Ron has been on a pro American extinction bender lately. “Yay below replacement fertility rates!”

  14. “Exposure to lead is undeniably harmful to human health. And perhaps it has contributed to lower U.S. fertility rates. But it seems more likely to me that U.S. fertility rates have fallen largely because Americans are choosing to have fewer children.”

    i wonder if the three students who did the lead study have a more underlying agenda, which if they were to state would diminish peer acceptance, and the author of the article engaging in the same type of economic deflection by rebuking the lead theory.

  15. the reality is that women entering the work force from the 1960’s onward is the catalyst.

  16. the labor force participation rate among women has double from 30% in 1948 to 60% in 1999…seems to be the elephant in the room.

    1. It’s not just the labor force participation rate; it’s easy to take a break from a low skill job to have kids. It’s that many of those jobs are professional, highly competitive careers where leaving the job market for a few years comes with high costs.

  17. or giraffe if your name is katie burke.

  18. It’s pretty obvious what’s responsible for the baby bust: women of child-bearing age pursue higher education and careers instead of founding families. If you go to college and grad school in your 20’s and then try to start a professional career in your 30’s, there just isn’t much time left for having kids. A secondary effect is that highly educated women tend to be very selective in who they choose as partners.

    There is, of course, nothing wrong with women to choose to get educated or to choose not to have kids. But in the US and Europe, this isn’t just a choice, it is heavily subsidized by forced transfers of resources from men to women via the government. In a free market without transfers, many women after high school would reach the conclusion that marriage and having kids is a more economically rational choice than making a massive investment in a professional career and then trying to have a kid mid-career.

    The government-mandated social safety net that the US and Europe have also mean that parents simply don’t need to rely on children anymore to help them in old age, so one historically significant motivation for having children also disappears.

    Low birth rates are likely in significant part a consequence of a progressive welfare state. I suppose the problem is self-correcting, in that the same social welfare state simply cannot finance itself anymore when births drop below replacement rate, though dealing with the consequences will be painful anyway.

    1. How do you explain Japan, Korea, Taiwan,Singapore? The birth rates have plummeted but these countries aren’t much of a welfare state. Nor are they particularly feminist. Women stop working after having children. They have homogeneous populations. They have very low out of wedlock births. They are an example of shame culture plus conservatism plus hyper competitiveness plus low social welfare plus low diversity. And they are even more fucked than the US or Europe.

  19. “Between 1973 and 1996, the U.S. completed the process of totally eliminating lead as an additive in gasoline.” Not entirely true. Piston engine (generally small aircraft) still burn 100LL fuel in America. LL meaning low lead. Minor point, but 100LL is still alive and well, the FAA’s attempts to replace it with no lead gas is of course proceeding at the rate of government work— slow at best. I think many race cars at your local dirt tracks and what not still do as well.

    Carry on.

  20. So lead in your gas tank = no lead in your pencil, so to speak?

    Apologies if that joke has already been exhausted. I feel it’s probably running on fumes as it is.

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