Each year, we hear that people are gaining weight and that chronic health problems like obesity, heart problems, and diabetes are on the rise.  It’s commonplace to ascribe these trends to personal lifestyle choices, such as the lack of exercise and diet, as well as the increasingly pervasive nature of fast food and processed, high-sugar foods.

However, there may be additional risk factors that are harder to control, such as genetics, and—as  a provocative new article in PLoS One (open access) suggests—birth order.  Specifically, first-born children might be more prone to these kinds of chronic health issues later in life:

Recent work has suggested that birth order may be a non-modifiable risk factor for obesity. Current evidence suggests that first-born infants grow faster than later-born infants. Dunger et al. suggest that the in-utero growth of first-born babies may be restrained as they have lower birth weight and accelerated post-natal catch-up growth, both of which are risk factors for obesity and cardiovascular and metabolic diseases, in adult life. However, whether first-born individuals have elevated metabolic risk in adulthood remains unknown. A recent study found that first-borns had a 4-fold risk of increased fat mass in early adulthood compared to later-borns. Neither of these studies evaluated the magnitude of metabolic risk induced by such greater weight and adiposity.

…Here we investigate the associations of birth-order with metabolic phenotype in early adulthood using data from a birth cohort of Brazilian young men. We tested two hypotheses. First, we wanted to confirm that first-born status was associated with low birth weight and faster infant growth. Second, we tested the hypothesis that metabolic risk was increased in first-borns compared to later-borns.

What did they find? What implications might their work have for public health given the kinds of global population changes we expect over coming decades?

Some results (excerpts):

• After adjusting for family income, maternal education, household assets score and maternal smoking in pregnancy, first-borns had significantly lower mean birth weight.
• First-borns also showed faster weight gains during infancy and had greater mean height and weight at 43 months.
• This greater weight and height tracked into early adulthood, with first-borns being significantly taller and heavier than later-borns.
• Total cholesterol and low-density lipoproteins were higher among first-borns.
• Our analysis suggests that low birth weight does not itself explain the increased metabolic risk associated with birth order. Rather, rapid post-natal weight gain appears most important, although such rapid growth is itself a response to low birth weight. Broadly similar growth patterns have been linked to the occurrence of type 2 diabetes and coronary events in adults.

So why do these patterns happen?  Here is their hypothesis:

The lower birth weight of first-borns can be attributed to materno-fetal physiological interactions. Following implantation, cells from the outer layer of the blastocyst, known as trophoblast, invade the maternal endometrium and alter the structure of the arteries that transfer blood to the placenta. Such modification decreases maternal resistance and increases placental blood flow. These changes then impact on the placental dynamics of subsequent pregnancies, such that second-born neonates are well known to have higher average birth weight than first-borns. Dunger et al. suggested that first-born children have higher glucose levels compared to later-borns, an effect most likely due to the combined effect of insulin resistance due to the increased adiposity and to the possible in utero programming of the insulin glucose axis. Thus, the increased adult body weight and adiposity of first-borns is likely to be induced at least in part by the maternal constraint of intra-uterine growth. However, other mechanisms may also be important. There is preliminary evidence in animals and in humans, that the novel experience of the first pregnancy could raise the level of apprehension in primigravid women, thereby potentially affecting the growth of the foetus via modulation of the vascular and endocrine functions of the feto-placental unit. Maternal emotional stress is an established risk factor for low birth weight, intrauterine growth retardation, preterm delivery and still-birth. Specifically, circadian cortisol secretion pattern appears to be distinctive in primiparous women and an alteration of the hypothalamus-pituitary axis (HPA) function could modify maternal glucocorticoids levels and affect foetal development. Possible mechanisms for birth-order effects on foetal growth merit further research.

And what potential implications might this have for the health of the global human population as we approach 9 billion people on the planet by 2050 and move through demographic transitions, such as reduced family sizes (emphasis mine)?

Our findings contribute to understanding of the early origins of adult disease. Our data show that a demographic factor relevant to all human populations can generate variability in both early growth and later metabolic risk. These findings also have important implications for understanding the increasing prevalence of the metabolic syndrome worldwide, where many populations are undergoing demographic change in response to economic development. Globally, there is a trend towards lower fertility rate, such that increasing proportion of individuals will be first-borns. In Brazil, for example, the average number of children per women (total fertility rate) dropped from 6.0 in 1960 to 1.8 currently.

They conclude with several important qualifications:

[A] number of questions still merit attention. For example, studies should describe in more detail the growth patterns that appear to lead to elevate metabolic risk, and identify the optimal time periods for intervention. Studies should also clarify the relative contribution of different possible underlying mechanisms (growth patterns, psychological factors) to the effects that we observed in these samples. Third, more research is required to establish the magnitude of the effect, whether it is similar in men and women, and whether it amplifies with age, as adverse metabolic profile consolidates. In these samples of young adults, the magnitude of the effect was relatively small, but degenerative diseases are expressed primarily from middle age and early-life effects tend to become more important through adulthood.

Siervo, M., Horta, B., Stephan, B., Victora, C., & Wells, J. (2010). First-Borns Carry a Higher Metabolic Risk in Early Adulthood: Evidence from a Prospective Cohort Study PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0013907

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In a forthcoming article in the Proceedings of the National Academy of Sciences, Patric Allard and Monica Colaiácovo use a nemotode (round worm) system to explore how BPA damages genetic processes in animals.

BPA ranks among the highest production volume chemicals with a global annual production scale of ≈4 million metric tons. It is commonly used in the manufacture of several polymers, including polycarbonate and epoxy resins. Thus, BPA is found in a variety of items such as plastic bottles, the lining of both food and beverage cans, and dental sealants. Consistent with its widespread presence, urinary BPA is detected in >90% of the population in the United States. Higher levels of urinary BPA have been correlated with cardiovascular diseases and diabetes and may be associated with an increased risk for miscarriages.

Their results?

Using these conditions, we observed a sixfold reduction in the mean number of eggs laid (increased sterility) and a dramatic increase in embryonic lethality (97.3%; n = 333) in worms exposed to 1 mM BPA compared with vehicle. Furthermore, none of the rare larvae observed either reached adulthood or survived after 3 d in culture (100% larval lethality). Taken together, these phenotypes indicate that BPA impairs C. elegans reproduction and are suggestive of errors in chromosome segregation.

Why was this?  They found that worms exposed to BPA had dysfunctional DNA repair mechanisms that ordinarily fix breaks in genetic material.  It turns out that BPA exerts hormone-like effects and turns off the gene that makes the DNA repair proteins.

Without these repairs, the animals were not able to produce eggs (in an important cell division process called meiosis) with normal genetic material.  This led to incorrect chromosome alignment and separation in the cell division of embryonic worms.

Bottom line:  Exposure to BPA caused these worms to become sterile and exhibit elevated emrbyonic mortality.

There’s always a challenge in using lab animal models to extrapolate to human health.  One of the main criticisms of these kinds of studies is that the exposure concentrations are different than what people are experience on a daily basis.  The authors address this (emphasis mine):

We examined the internal levels of BPA following our exposure protocol and found that worms contained on average 2 μg/g of unconjugated BPA. These levels were within the range or lower than the internal free BPA levels detected in maternal kidneys, liver, and uterus, as well as in fetal liver and total fetal homogenate of pregnant rats perfused with a single dose of BPA at 10 mg/kg. Data on nonblood tissue levels of BPA both in rodent models and in humans are scarce and intraorgan concentrations in the BPA study on mouse meiosis were not measured, making direct exposure comparison difficult. However, it is likely that both our results and those of Susiarjo and colleagues represent the reproductive outcome following elevated BPA exposure. Therefore, our studies bear relevance to occupational exposure studies in humans, and particularly to fetal and neonate exposure levels, as suggested by the up to 10 times higher levels of BPA detected in premature infants in neonatal intensive care units.

Patrick Allard and Monica P. Colaiácovo (2010). Bisphenol A impairs the double-strand break repair machinery in the germline and causes chromosome abnormalities Proceedings of the National Academy of Sciences : 10.1073/pnas.1010386107

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In 40 years, there will be about 3 billion additional people living on the Earth (~9.5 billion total).   With all of these new folks, it’s easy to think about the added demands of energy, food, and water required to sustain their lifestyles.  And in terms of climate warming, it’s hard to escape the fact that significantly greater energy consumption will lead to rising rates of carbon emissions, unless there’s a shift to decarbonize the economy.

In this week’s early Edition of the Proceedings of the National Academy of Sciences (open access), Brian O’Neill and colleagues note that emissions are not just controlled by the sheer size of the human population but also by important demographic changes.

For example, how might an aging or more urban population affect emissions?  How about changes in household size?  Modelers of carbon emissions don’t usually ask these kinds of questions, so the conventionally projected emissions might be off if these additional demographic details matter.

The researchers developed a global economic model (Population-Environment-Technology, or PET) in which they specified relationships between demographic factors like houshold size, age, and urban/rural residency and economic factors like the demand for consumer goods, wealth, and the supply of labor.  Here’s a bit more on how this works:

In the PET model, households can affect emissions either directly through their consumption patterns or indirectly through their effects on economic growth in ways that up until now have not been explicitly accounted for in emissions models. The direct effect on emissions is represented by disaggregating household consumption for each household type into four categories of goods (energy, food, transport, and other) so that shifts in the composition of the population by household type produce shifts in the aggregate mix of goods demanded. Because different goods have different energy intensities of production, these shifts can lead to changes in emissions rates. To represent indirect effects on emissions through economic growth, the PET model
explicitly accounts for the effect of (i) population growth rates on economic growth rates, (ii) age structure changes on labor supply, (iii) urbanization on labor productivity, and (iv) anticipated demographic change (and its economic effects) on savings and consumption behavior.

Although there are some exceptions, households that are older, larger, or more rural tend to have lower per capita labor supply than those that are younger, smaller, or more urban. Lower-income households (e.g., rural households in developing countries) spend a larger share of income on food and a smaller share on transportation than higher-income households. Although labor supply and preferences can be influenced by a range of nondemographic factors, our scenarios focus on capturing the effects of shifts in population across types of households.

To project these demographic trends, we use the high, medium, and low scenarios of the United Nations (UN) 2003 Long-Range World Population Projections combined with the UN 2007 Urbanization Prospects extended by the International Institute for Applied Systems Analysis (IIASA) and derive population by age, sex, and rural/urban residence for the period of 2000–2100.

What did they find?

Although a shift to older and more urban household types occurs in all regions, changes in urbanization levels are most pronounced in China, sub-Saharan Africa, and the ODC [Other Developing Countries] region. Changes in household age strongly affect the European Union (EU) and other industrialized countries (OIC) regions as well as Latin America. Household size changes are largest in India, ODC, and Latin America.

….Results show that the effects of changes in population composition can have a significant influence on emissions in particular regions, separate from the effect of changes in population size. Aging can reduce emissions in the long term by up to 20%, particularly in industrialized country regions. Aging affects emissions in the PET model primarily through its influence on labor supply. In the model, aging populations are associated with lower labor productivity or labor force participation
rates at older ages, which (ceteris paribus) leads to slower economic growth. In contrast, urbanization can lead to an increase in projected emissions by more than 25%, particularly in developing country regions, also mainly through effects on labor
supply. The higher productivity of urban labor evident in the household surveys implies that urbanization tends to increase economic growth. Although other studies find that, controlling for income, urban living can be more energy efficient, survey data for urban households include income effects and therefore result in increased emissions.

In most regions, changes in household size have little additional effect on emissions beyond those already captured by aging (older households are also typically smaller). This result could be because of limitations in our household projections, which include household size changes driven by aging and urbanization but only capture the effects of behavioral change on household size in China and the United States. In China, reduced household size leads to lower emissions, a direction of influence counter to previous results. The reduction is driven primarily by the fact that large
households in older age categories typically have greater per capita labor supply (and income) than smaller households, because they include adult children of working age. Thus, aging, combined with a decline in household size, leads to a reduction in
per capita labor supply as older households become composed primarily of the elderly.

And the overall take-home message on emissions reductions?

[R]educed population growth could make a significant contribution to global emissions reductions. Several analyses have estimated how much emissions would have to be reduced by 2050 to meet long-term policy goals such as avoiding warming of more than 2 °C or preventing a doubling of CO2 concentrations through implementation of a portfolio of mitigation measures characterized as “stabilization wedges”. Our estimate that following a lower population path could reduce emissions 1.4–2.5 GtC/y by 2050 is equivalent to 16–29% of the emission reductions necessary to achieve these goals or approximately 1–1.5 wedges of emissions reductions. By the end of the century, the effect of slower population growth would be even more significant, reducing total emissions from fossil fuel use by 37–41% across the two scenarios.

O’Neill, B., Dalton, M., Fuchs, R., Jiang, L., Pachauri, S., & Zigova, K. (2010). Global demographic trends and future carbon emissions Proceedings of the National Academy of Sciences, 107 (41), 17521-17526 DOI: 10.1073/pnas.1004581107

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There has been a lot published recently on the source of happiness and what constitutes the good life, with many articles focusing on levels of personal income that mark tipping points, such as the recent claim that we need $75,000 to be happy.

In this week’s Early Edition of the Proceedings of the National Academy of Sciences (open access), Bruce Headey and colleagues describe how happiness is also being explored in terms of fundamental differences between psychological and economic theory:

Research on life satisfaction or happiness used to be a minor branch of psychology, became a major branch, and then in the past decade has attracted huge interest among economists. Some of these economists now use satisfaction measures as proxies for the outcome which economic agents are assumed to maximize—namely, individual utility. But the assumptions and findings of psychologists and economists are contradictory.

In one corner, psychological theory:

The dominant theory in psychology is probably still set-point theory…[which] holds that long-term adult happiness is stable—it has a setpoint—because it depends mainly on genetic factors, including personality traits molded and expressed early in life. It has been shown that major life events can temporarily change happiness levels, but that most people revert to their previous setpoint within a year or two. The theory can be summarized by saying that, “We are all on a hedonic treadmill”.

…An obvious implication is that neither individual choices nor public policy can make a substantial long-term difference to happiness.

In the other corner, economic theory:

Economists who, following the recent advice of the Commission on the Measurement of Economic Performance and Social Progress, now intend to use direct satisfaction-based measures of utility [happiness] must necessarily assume the opposite. There is no point in deploying such measures if individual preferences, behavioral choices, and public policy could not increase long-term satisfaction.

Research on happiness (relabeled as subjective utility) by economists developed rapidly in the 1990s, ironically just as setpoint theory became dominant… Economists have not developed a counter theory, but pursue a strategy of seeking to account for variance in life satisfaction due to individual utility maximizing behavior and policy interventions.

Economists have also developed explanations for why happiness may not appear to change over time that have nothing to do with happiness set points:

…Contrary to what a layperson might suppose, modern economists, starting with Richard Easterlin (the Easterlin paradox), have repeatedly claimed that money does not buy much happiness, especially in wealthy Western countries. The paradox
has been challenged…but critics have never been able to show that long-term income growth produces long-term gains in happiness. This nonoutcome arises mainly because rising incomes are subject to social comparisons with the neighboring Jones’s, whose incomes also keep going up. People adapt to their own and their neighbors’ new levels of income by raising their expectations, with the result that no lasting increase in happiness occurs.

How do you study these ideas?  By using an enormous data set:

…The German Socio-Economic Panel Survey (SOEP) provides by far the longest data series available worldwide. It reports interviews with a very large national representative sample aged 16 and over, who have answered questions about their life satisfaction every year from 1984 to 2008.

What did they find, and who cares?

During this quarter-century, large numbers of respondents recorded substantial and apparently permanent changes in satisfaction…[T]he scale of change indicates that set-point theory is seriously flawed. A key implication is that the economist’s goal of enhancing (subjective) utility via changes in individual behavior and public policy is not condemned to inevitable failure by human psychology. Nonfixed, nongenetic factors, including individual choices and public policy, may influence satisfaction levels, or utility so measured.

The authors go on to talk more about life factors that drive happiness, showing that things people can change about their lifestyle matter as much or more than personality traits or being married—things we might consider to be fixed in our lives.  Some we’ve heard before, but other insights are new and interesting (emphasis mine):

…[W]e have shown that life goals, religion, and personal choices matter for happiness. Key choices relate to one’s partner, the tradeoff between work and leisure, social participation, and healthy lifestyle. Life goals and choices have as much or more impact on life satisfaction than variables routinely described as important in previous research, including extroversion and being married or partnered. If we use these last two variables as benchmarks, it appears that partner’s level of  neuroticism, one’s own commitment to family and altruistic goals, church attendance, participation in social events, and regular exercise are all equally or more important than being extroverted.

…For both men and women, doing fewer paid hours of work than they want apparently has close to the same impact on life satisfaction as not being married/partnered. For women, being obese actually reduces life satisfaction more than not having a partner.

…people who find themselves working much more or less than they want are significantly less satisfied with life than those who come close to making their preferred tradeoff between work and leisure. For both men and women, being underworked is much worse than being overworked, presumably because lost consumption rankles worse than lost leisure.

…people who consistently prioritize non–zero-sum altruistic goals or family goals are more satisfied with life than people who prioritize goals relating to their own careers and material success. Giving priority to altruistic goals is strongly associated with higher life satisfaction, whereas family goals are also satisfaction enhancing. Corroborating some previous research, it appears that prioritizing success and material goals is actually harmful to life satisfaction.

Headey, B., R. Muffels, and G.G. Wagner (2010). Long-running German panel survey shows that personal and economic choices, not just genes, matter for happiness Proceedings of the National Academy of Sciences : 10.1073/pnas.1008612107

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In the same issue of Population and Environment as the previous post, another article, by Chenyang Xiao and Dayong Hong— Gender differences in environmental behaviors in China—shows some interesting cultural differences compared to the study of the American public:

China represents the third largest economy and the highest level of
national carbon dioxide emissions when compared to other nations across the globe.
Yet, little social science research has focused on the environmentally oriented
behaviors of Chinese nationals, key to understanding levels of environmental
impact. This study examines, in China, gender differences in environmentally
oriented behaviors, environmental knowledge, and general environmental concern.
Making use of path analyses, we identify a pattern of gender differences similar to
common findings in the West: women demonstrated greater participation in environmental behaviors inside of the home (e.g., recycling), while outside of the home (e.g., environmental organization donations) no gendered patterns were exhibited.  However, Chinese women expressed lower levels of concern than men—a finding opposite of most Western studies. Also distinct from other settings, in China, higher levels of knowledge regarding environmental issues did, indeed, translate into proenvironmental behaviors—thereby not exhibiting the knowledge-behavior gap
demonstrated elsewhere.

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In my series on why people don’t engage climate change, we saw major socioeconomic and demographic differences in how people perceive climate change.

In the current issue of Population and Environment, Aaron McCright authors an article, The effects of gender on climate change knowledge and concern in the American public, in which he examines whether women and men perceive climate warming differently:

This study tests theoretical arguments about gender differences in scientific knowledge and environmental concern using 8 years of Gallup data on climate change knowledge and concern in the US general public. Contrary to expectations from scientific literacy research, women convey greater assessed scientific knowledge of climate change than do men. Consistent with much existing sociology of science research, women underestimate their climate change knowledge more than do men. Also, women express slightly greater concern about climate change than do men, and this gender divide is not accounted for by differences in key values and beliefs or in the social roles that men and women differentially perform in society. Modest yet enduring gender differences on climate change knowledge and concern within the US general public suggest several avenues for future research, which are explored in the conclusion.

McCright shares additional insights in a Michigan State University news story covering the article:

“Men still claim they have a better understanding of global warming than women, even though women’s beliefs align much more closely with the scientific consensus,” said McCright, an associate professor with appointments in MSU’s Department of Sociology, Lyman Briggs College and Environmental Science and Policy Program.

The study is one of the first to focus in-depth on how the genders think about climate change. The findings also reinforce past research that suggests women lack confidence in their science comprehension.

“Here is yet another study finding that women underestimate their scientific knowledge – a troubling pattern that inhibits many young women from pursuing scientific careers,” McCright said.

Understanding how the genders think about the environment is important on several fronts, said McCright, who calls climate change “the most expansive environmental problem facing humanity.”

“Does this mean women are more likely to buy energy-efficient appliances and hybrid vehicles than men?” he said. “Do they vote for different political candidates? Do they talk to their children differently about global warming?”

McCright analyzed eight years of data from Gallup’s annual environment poll that asked fairly basic questions about climate change knowledge and concern. He said the gender divide on concern about climate change was not explained by the roles that men and women perform such as whether they were homemakers, parents or employed full time.

Instead, he said the gender divide likely is explained by “gender socialization.” According to this theory, boys in the United States learn that masculinity emphasizes detachment, control and mastery. A feminine identity, on the other hand, stresses attachment, empathy and care – traits that may make it easier to feel concern about the potential dire consequences of global warming, McCright said.

“Women and men think about climate change differently,” he said. “And when scientists or policymakers are communicating about climate change with the general public, they should consider this rather than treating the public as one big monolithic audience.”

McCright, A. (2010). The effects of gender on climate change knowledge and concern in the American public Population and Environment, 32 (1), 66-87 DOI: 10.1007/s11111-010-0113-1

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That’s the title of a new article¹ by Suzanne Petroni in the latest issue of Population and Environment (subscription required). She begins by acknowledging the complex history between these issues:

There is, in the field of population and reproductive health, a present debate around the merits and deficiencies of bringing the issue of global population growth back to the public agenda. Many see the current attention to the issue of climate change as an opening in which to make the case that global warming can not be alleviated or reversed without slowing population growth. They believe that linking population growth and climate change will help governments to see the exigency of the matter, and will place family planning back into the political realm as an urgent matter of national and environmental security….

But others worry that focusing on the environmental impacts of demographic change places at risk the hard-fought and long-developed global consensus that individual rights and empowerment are what matters most in fostering just and sustainable development. They fear that a renewed focus on the impacts of the growth of our global population poses a risk of drawing the international community back to numbers-driven policies and programs, which have not always prioritized individual interests…

• [D]oes the right of the community to live on a healthy planet trump the right of the individual to decide for him or herself, without external pressure, their own desired level of fertility?
• Does the United States, which emits a hugely disproportionate amount of greenhouse gases, have a right to suggest that other countries reduce their rates of population growth in order to somehow compensate for our profligate and consumptive lifestyles?
• How can we best balance a duty to future generations with the values of individual freedom and equality among the planet’s current occupants?
• And, while coercive means of population control have been widely condemned in most parts of the world, does making the ‘‘population-climate change connection’’ run the risk of countries seeing population control as an ‘‘easy fix’’ to the environmental challenges we face?

In light of these huge questions, what are her recommendations?

She begins with implicit reference to Commoner’s and Ehrlich’s I = P * A * T tool, where impacts (I, in this case greenhouse gas emissions) equal population (P) times Affluence (A) times technological impact (T, in this case the carbon intensity, or the amount of carbon emitted per dollar spent on economic activity).

If we want to reduce environmental impact I (greenhouse gas emissions and warming in this case), she argues that we have so far done so by focusing primarily on reducing T through new technology.  Why?  Because reducing A is not an easy proposition when three billion people live on less than $2 per day.  And reducing P has been politically difficult.  She describes how the current mode of thinking leads to difficulties but that if we try to be a bit more creative, we can work around the challenges:

Undeniably, if the IPCC or others were to approach the population issue with any suggestion of coercion as a means to limit population growth, they would likely find near-unanimous support for their decision to avoid the issue. But is there room for an ethical argument to slow population growth through voluntary family planning as a way to lessen climate change? Can we speak of environmental preservation, individual rights, justice and slower population growth in the same breath?

Some excerpts:

• While consumption is clearly the primary driver of environmental degradation, including climate change, it appears evident that population growth, both in industrialized or developing countries, is a contributing factor. If population growth is proven to be destructive to public health and the natural environment, then governments have an obligation to intervene to lessen this damage.
• Engendering support among the American public and policymakers for voluntary family planning—at home and abroad—is indeed a worthy and important task. Contrary to the arguments of Malthus and Hardin that providing assistance to those in need will lead to greater population growth, rampant starvation, declining health outcomes and environmental degradation, the consequences of voluntary family planning over time have rather been quite the opposite. Given adequate information and access to services, couples around the world have chosen to have fewer children, thereby contributing to better health outcomes and diminished negative impacts on the environment…It is thus quite morally acceptable to promote greater investments in international family planning, with appropriate caution. Most critically, population and family planning policies must prioritize freedom and justice, and must be made with the individuals at the core, because in the end, it is individuals—not abstract millions—with whom we share the planet.
• Further, population policies must advance a broad range of social needs, and not be adopted in isolation. As the nation’s top ethicists concluded in 1971, ‘‘The ultimate goal of a population policy should be human welfare, and not only such proximate goals as a reduction of population growth rates’’ (Institute of Society, Ethics, the Life Sciences 1971)
• Investing in the education of girls, the conservation of natural resources and in other socio-economic programs aimed at improving the quality of life of individuals and families around the world will contribute to the outcomes we want: a healthy planet that can be sustained for generations to come. And it will do so by contributing to the general welfare in an ethical and principled manner.
• Moving the discussion forward in a just and ethical manner also requires emphasizing first and foremost a responsibility on the part of Americans to act to mitigate the harm that we ourselves are doing to the global environment. If we take seriously a duty to leave a healthy planet for future generations, our current patterns of consumption must change. Such a focus has not only practical benefits, but political ones as well. Namely, if we wish to be a credible voice for solving the challenge of climate change, we must give primacy in our dialogue to reducing our own country’s production of emissions.
• Done well, a thoughtful and deliberative dialogue around the contribution of voluntary family planning to mitigating climate change can help Americans to better understand the significant role that the United States plays in the world; not solely as consumer and polluter, but also as an important member of a global commons, and yes, as a beneficent donor. If embarking upon such a discussion leads to greater support for renewed US contributions in this area, it will achieve a great deal of good.

She also cautions that connecting population and climate change has its risks:

Perhaps of greatest concern is the prospect of somehow enabling a return to the coercive policies of the past (and present, as in the case of China), which have been proven unjust and damaging to the rights of many individuals, couples and communities. Articulating a close interrelationship between rates of population growth and greenhouse gas emissions poses the prospect of countries which are under pressure to reduce their emissions to consider a ‘‘simple’’ solution to climate change: reducing their rates of population growth. If done without proper regard for human rights, such policies could turn coercive and prove devastating to individual rights and well-being, all in the name of environmental stewardship.

Perhaps more subtly, making this argument in the United States could encourage individuals in this country to blame—wrongly—population growth in the developing world for the problem of climate change…It would be highly unethical to enable the transference of responsibility to the poorest people in the world for a problem towards which the United States has been the primary contributor. Wealthy nations, including the United States, must resist the temptation to shift such culpability, just as they must resist pressuring poorer countries to remain so in order that those living in rich nations do not suffer.

It cannot be left unstated that raising the issue of population growth in the United States would inevitably provoke the similarly controversial issue of immigration.

The risk of alienating a key base of supporters in the form of feminists and human rights advocates around the world is very real if advocacy arguments are not tendered cautiously.

¹Petroni, S. (2010) Policy review: thoughts on addressing population and climate change in a just and ethical manner. Population and Environment DOI 10.1007/s11111-009-0085-1

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Lydia DePillis has an interesting article over at The New Republic based on a new report from the United Nations.

Is climate change gender-neutral? Not according to the U.N. Population Fund, which earlier today released a report arguing that women suffer disproportionately from the impacts of global warming. Especially in developing countries, they can’t flee changes like desertification and sea-level rise as easily as young men, who aren’t as tied to children and households. They’re often caught up in civil conflicts ignited by scarce resources. And they’re more likely to fall victim to diseases caused by wetter weather patterns.

But on the flipside, the report argues, women are also in the best position to help mitigate both the causes and effects of rising temperatures—which is why policies to empower women, like targeted microloans and reproductive healthcare, shouldn’t be treated as separate from climate policy.

…Think of it as Nick Kristof meets Tom Friedman: keeping “women’s issues” separate from “climate issues” is a huge missed opportunity.

I love this conclusion.  It’s one of the things that environmental studies (ES) programs in higher education need to focus on—better connections to groups not traditionally affiliated with ES, such as Gender and Women’s Studies, Africana Studies, Psychology, Religion, visual and performing arts, etc.  For major environmental challenges like climate warming, everyone needs to be part of this conversation.

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Every day, we are exposed to a cocktail of synthetic chemicals from consumer products.  How harmful are these?  In an earlier post, I described how risk analysis is an important scientific process for determining exposure, effects, and overall risk of these chemicals.

One thing missing from these analyses is how people respond to information about their chemical exposure.  In a recent issue¹ of the Journal of Health and Social Behavior, Rebecca Altman and colleagues addressed this by analyzing what they call the “exposure experience” of women in Cape Cod, MA—an area with elevated breast cancer rates.

What did they find?

As part of a larger analysis (Silent Spring Institute’s Household Exposure Study), they measured 120 homes for 89 chemicals that could affect hormones.  They also measured blood and urine concentrations in a sample of female residents.

They found that after receiving the chemical concentration data about their homes, participants concluded one or more of the following statements:

• Synthetic chemicals can be detected in household air and dust, and in human samples such as urine (e.g., “There’s chemicals everywhere in this place!”)
• Most homes have chemicals.
• Homes contain a variety of different chemical compounds.
• Even banned substances, such as the pesticide DDT, were detected.
• There are numerous sources for chemicals found in urine, blood, and household air and dust.
• Many common, household sources of chemical exposures are unregulated or understudied.

The response of many of the women included follow-up questions like

• Do these results signal a problem?
• What is “acceptable”?
• Where are these chemicals coming from?
• And, what should I do?

Altman and colleagues argued

In response to these circumstances, study participants reached out to others. As indicated in the previous excerpt, participants contacted the scientists, but they also queried friends and family (e.g., a friend with cancer, a daughter with a medical degree, or a son with scientific training). They shared study results with their physicians or oncologists. Some participants consulted Internet resources or local libraries. One participant copied the results for her landscaper, who had applied pesticides to her lawn and garden. Yet, as these participants reported, their friends and contacts—including their physicians—had few new insights to offer. Left unresolved were lingering questions: Participants’ narratives reflected puzzlement over how to interpret levels and make appropriate responses.

The research team noted that the participants were surprised by the number of chemicals detected in air and dust, and they weren’t sure where they could come from because the women perceived themselves using few chemicals.  It turns out, as Altman’s team discovered, they were actually using several products containing these chemical, illustrating the disconnect between consumer culture an its associated chemical exposure risks.

Another trend:  One of the first reactions of the participants was to attribute chemical levels to historical uses in the home, often citing the age of the home.  But, again, this reflects the tendency to look for explanations beyond current consumption patterns.

They also found that participants may have underestimated the threat of chemical concentrations in their homes.  When examining a graph showing the chemical concentrations in their home relative to all other participants’ homes and the EPA guideline level, many participants shrugged off their results as “average” when their home fell in the middle of the data values even when all of the data were above the EPA safety guideline.  As Altman noted,

[f]or most participants, this perception of “average-ness” allayed concerns of health risk.

When the participants were concerned about the levels of chemicals in their homes, Altman argued that they sometimes fell victim to bad mental models of what to do:

• technological fallacy—that it’s simply a matter of cleaning them up
• consumption fallacy—that it’s simply a matter of switching products, when in reality (1) it’s often not clear how to do this, (2) there may be no good alternatives for certain products, or (3) switching may do no good.   When one woman learned that she had pesticides in her urine, despite eliminating them from her home and eating organically, she was understandably shocked:
  It was overwhelming to know how many chemicals they found in my house, especially like I’ve already said, I’ve made really conscious efforts to eliminate so many things [pesticides]—my lawn, everything on the food that I eat. I have a water filtration system that cost me a thousand dollars to, you know, to purify my water. I’ve made so many, many little things like that … and to know that even so many years after my diagnosis, to know that I’m still being exposed. It’s overwhelming.

Interestingly, when confronted with the notion that chemical levels remained high even after efforts to reduce them, several of the participants began controlling them symbolically, for example, by dissociating pesticides sprayed in the neighborhood with those found in their homes or bodies.

Bottom line:

One of the conclusions that Altman draws is that scientists conducting risk analyses need to think about the context/starting assumptions that people have regarding scientific exposure data.  Specifically, it’s not enough for scientists to think about how to present uncertainty in the data; they also need to understand the “unique social and historical setting” in which the data are interpreted.

These stories make a compelling case that sociologists are (should be) an important part of the risk analysis process.

Related post: Do our daily routines put our health at risk?

¹Altman, R. (2008) Pollution comes home and gets personal: Women’s experience of household chemical exposure. Journal of Health and Social Behavior 49(4): 417-435.

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Photo credit:  http://www.flickr.com/photos/tzofia/ / CC BY-NC-ND 2.0

Prerequisite posts:

• Why don’t people engage climate change?  Overview
• Why don’t people engage climate change?  Problem 1: Environmental Literacy
• Why don’t people engage climate change?  Problem 2: Communication

In earlier posts, we examined climate change engagement as problems of environmental literacy and communication.  There is no doubt we can do better with both of these.  But as we will see, proponents of environmental literacy and communication make a mistake if they believe engagement is simply a matter of getting more information to people.  Science, it is believed, will speak for itself.

Unfortunately, it often doesn’t.

A political scientist recently told me that before the age of 25, people use information to shape their value system and perceptions of the world.  After 25, they start cherry picking information that simply reinforces these beliefs (hence the world of cable news).

Although this is is a rough generalization, it suggests that a person’s values development may have a shelf life.  It also reveals why issues like climate change may not resonate with people cut from certain ideological cloths—no matter how much information they encounter.

The psychology, sociology, and ethics literature has a lot to say about this problem.  For simplicity, I want to pull out four challenges I think are among the most common and important with respect to climate change…

Challenge 1: Problems that are global in nature and distant in the future are not considered urgent

Matt Nisbet’s article¹ that we looked at last time contained another Pew poll that came out earlier this year, asking Americans which issue should be Obama’s top priority:

If you look at how priorities of Americans are changing over the past two years, some pretty obvious trends show up:

• It’s the economy—people are worried about their jobs.
• At the bottom of the table, the percentage of people who think protecting the environment is a top issue has fallen from 57% to 41%.
• Climate warming is dead last, falling from 38% to 30%.

These kinds of data are not new.  Quality of environment is generally a latent concern for most people.  But when asked to rank the importance of things like climate change against other issues that are personal (economy, health care) or are easily manipulated for political gain (terrorism, deficits), environmental concerns usually lose.

Update: The new Bureau of Labor Statistics data out today are grim:

Challenge 2: Cultural identity shapes perceptions and responses to environmental issues

Earlier this year, the Yale Project on Climate Change and the George Mason University Center for Climate Change Communication published a report¹ called Global Warming’s Six Americas 2009: An Audience Segmentation Analysis (Maibach et al. 2009).

There were a number of important outcomes of this study that have wide-ranging implications for climate change, environmentalism, and environmental studies programs.

The first interesting point is that they identified six clusters of Americans falling along a spectrum from alarmed to dismissive about climate change:

There are three larger groups here:

• Those that get climate warming—the alarmed and concerned (54%)—make up a majority of Americans.
• The cautious and disengaged (31%) are on the sidelines, either not sure about climate change or not perceiving it to be a salient issue.
• The doubtful and dismissive (18%) are the climate warming skeptics and deniers.

So what do these groups mean in terms of engagement with and commitment to climate warming?

These statistics are eye-opening:

• A full 82% of Americans have not yet engaged climate warming personally.
• Almost half (49%) have not yet been convinced that warming is happening or they are actively hostile towards it.

Who are these folks relative to what a “typical” American looks like demographically?

These data are also eye-opening.  You can read the demographic breakdowns in the figure, but a number of things stand out:

• This is why climate warming is also an issue of race, gender, class, education, and religion. All of these frames shape personal values regarding climate warming.  It means that we need to do a better job of engaging all of these constituencies.
• People of color are falling out disproportionately in the disengaged group.
• Blue-collar folks are in the cautious group on the sidelines.
• Religion is a correlate with those doubtful or dismissive of climate warming as well as those disengaged.

Challenge 3:  People don’t see personal harm arising from climate change within their lifetimes

The Maibach article also speaks to this challenge.  In the figure below, they ask two questions:

• How much do you think global warming will harm you personally (left panel)?
• How much do you think global warming will harm future generations (right panel)?

As you can see in the left graph, there’s a lot of brown (only a little and not at all) and gray (don’t know).  More people think they will die from cancer, a heart attack, or an auto accident than being harmed by climate warming.

However, when the audience thinks about future generations, they think that there is greater risk of harm.

This distinction may help with the climate change communication challenge in the earlier post.  In fact, if you’ve had a chance to see climate modeler James Hansen talk recently, this is one of his pitches.  He frames the impacts of warming in terms of the harm his grandchildren will experience.

Challenge 4: Some climate-impacting behaviors are easier to change than others

Dramatic reductions in carbon emissions in a short period of time are going to require significant behavioral changes in transportation, diet, and powering our lives.  Unfortunately, we are creatures of habit.  And our lifestyles are locked in based on things like how our homes, cities, and roads were designed decades ago and the kinds of transportation available to us.

As mentioned in an earlier post, a paper out this week by Tom Dietz and colleagues suggested that policy measures like cap and trade could take years to implement.  Why not take a look at how much readily available technologies in U.S. homes could potentially reduce emission in the short term?

How much of a difference could households make? According to Dietz et al., they are

• 38% of the overall US carbon emissions
• 8% of global emissions
• larger than the emissions of any single country except China

So if we could modify behaviors associated with household energy use, we might be able to bring about relatively quick and possibly large reductions.  The outlook is mixed, however, as suggested by this table:

Some main points:

• Home weatherization is behavioral low-hanging fruit.  People are willing to do these things because they both save money and are good for the environment (probably in that order).  The good news is that there are sizable reductions that can be achieved.
• Driving is the tough nut to crack.  People are simply unwilling to change driving behavior or carpool.  The bright spot here is fuel efficiency.  People are willing to drive cars with better gas mileage, so this behavior should continue to be encouraged with tax credits for hybrid and electric vehicles.

Related posts:

• Why don’t people engage climate change?  Overview
• Why don’t people engage climate change?  Problem 1: Environmental Literacy
• Why don’t people engage climate change?  Problem 2: Communication

¹References:

• Dietz, T. et al. (2009) Household actions can provide a behavioral wedge to rapidly reduce U.S. carbon emissions. PNAS 106(44):18452-18456.
• Maibach, E. et al. (2009) Global Warming’s Six Americas 2009: An Audience Segmentation Analysis. Yale Project on Climate Change and the George Mason University Center for Climate Change Communication
• Nisbet, M. (2009) Communicating Climate Change: Why Frames Matter for Public Engagement. Environment 51(2):12-23.

Photo credit:  http://www.flickr.com/photos/pagedooley/ / CC BY 2.0