Exposure to air pollution is linked to an increase in violent crime

The researchers were careful to correct for other possible explanations, including weather, heat waves, precipitation, or more general, county-specific confounding factors."

https://www.sciencedaily.com/releases/2019/10/191003114007.h...

Say what? You should write these scientists and explain, I'm sure they've never heard of this concept!

The authors are aware of this and attempt to control, mainly by assuming that all confounding effects are either constant or cyclical:

"We include county-by-year-by-month-by-day of the week fixed effects to control for county level unobservables that are either constant over time, such as state and county-level policies, or that are time-variant, such as changes in population density, demographic composition, seasonal variation in pollution or crime, or changes in state and county-level policies that limit pollution or crime enforcement. These fixed effects also control for cyclical within-week, within-county variation in pollution and crime. Thus, our data allows us to compare for example, the effect of changes in pollution within a series of Mondays within a given county within a given month. We argue that changes in pollution across a series of Mondays within a county-month, conditional on weather controls, is random and thus exogenous to crime."

I'm not at all convinced this holds true, however - lots of systems with humans in it are chaotic rather than cyclical. I imagine if you did a plot of population over time, it would be very noisy. All it takes is a bit of aperiodic noise in the population, and tight correlations between population/crime and population/pollution, and their effect is rendered void.

[0] https://xkcd.com/552/

[1] http://bayes.cs.ucla.edu/WHY/

"Pollution and crime rates may have common correlations with location and time-varying unobservables. For example, PM2.5 or ozone levels and crime rates may be correlated with county-level covariates such as traffic density, population density, demographics, and industrial activity. Failing to control for such covariates will lead to biased estimates of γPM and γo.

Our identification strategy explicitly addresses omitted variable bias in several ways.

First, we show that endogeneity with respect to violent crimes and pollution can be addressed by including a series of high-dimensional fixed effects. In our primary specification, we include county-by-year-by-month-by-day of the week fixed effects to control for county level unobservables that are either constant over time, such as state and county-level policies, or that are time-variant, such as changes in population density, demographic composition, seasonal variation in pollution or crime, or changes in state and county-level policies that limit pollution or crime enforcement. These fixed effects also control for cyclical within-week, within-county variation in pollution and crime. Thus, our data allows us to compare for example, the effect of changes in pollution within a series of Mondays within a given county within a given month. We argue that changes in pollution across a series of Mondays within a county-month, conditional on weather controls, is random and thus exogenous to crime.

Second, crime has been shown to respond to changes in temperature, and temperature is generally correlated with air pollution (Field 1992; Jacob et al. 2007; Ranson 2014). Thus, failure to adequately control for temperature, and weather more generally, will lead to biased estimates. To address this concern, we include temperature and precipitation splines in our primary specification, we provide robustness checks with alternative functions of temperature, and in Section 5.3 we perform a series of tests to show that our results are not confounded by unaccounted for variation between temperature and air pollution. For example, we show that effect of PM2.5 on violent crime is larger at lower temperatures, opposite of the effect of temperature alone."

Reading the title, I was expecting this to be a long-term relationship, and to happen at extremely high levels of air pollution. Particularly since the study on China last year showing that exposure to PM2.5 has lasting cognitive effects, which found variation at levels far higher than anything found in the US. And ozone at approved levels (but not PM2.5) has been linked to long-term cognitive decline.

Instead, this is claiming day-to-day variation based on that PM2.5 levels that are 25% of the EPA 24-hour exposure threshold, and even below the annual EPA standard. If you told me that air pollution below the EPA safe thresholds had a noticeable impact on cancer or emphysema rates, I wouldn't be surprised at all. But this is wild - a 5% increase in violent crime based on a day of pollution! For reference, one violent crime study I just checked finds that violent crime is about 10% higher in the summer than the winter in a cold city, and late-night crime (past midnight) is about 5% higher on weekends than weekdays. So 15 micrograms of PM2.5 is about as impactful as "people stay up late and get drunk on weekends".

It's an effect so bizarrely strong that my first reaction is to assume the study is bad or confounded. Except... all the obvious patterns don't work, and the controls look solid. Unpleasant weather keeps people inside and reduces (outdoor) crime. Shared causes like high human activity should have raised property crime rates. The effect looks stable across all kinds of temperature and crime subsets. If there is a confounder, it's presumably something strong and interesting.

> Pollution levels can easily rise by much more than that.

Very true, although I note that the effect doesn't seem to continue across the whole range studied. I wonder why effect falls off, and what happens in places that are always this polluted?

And even excluding road rage as the mechanism for violence, 10% more people doing actions all over the place can also just cause violence.

It is related to arguement from ignorance and Dunning-Kreuger effect in that it often assumes their comprehended issues are the end of all problems and that the objections may already be implicitly handled. Listing everything explicitly in exhaustive detail technically addresses it but would be both inefficient and bad communication from how overloaded it would get.

That said assuming uncovered issues are implicitly covered is itself a fallacious inference. It may be dickish pedantry that is wrong based upon incomplete information but not illogical given what is known and communicated.

This doesn't mean it is impossible, as rain might e.g. still be correlated with less traffic. The nature of a hidden variable is exactly that its indirect correlations would be not pinpoint-able in the data.

But IMHO this paper does a decent job of trying to account for lots of dimensions, and trying identify the existence of dominant hidden variables from the data at hand.

This is far from a rush job or a 'spurious correlation' piece of work, and its results most certainly are interesting and a very good basis for further investigation into an important observation. I'd even go further and say that these results warrant societal value systems that subscribe to the precautionary principle to take this on board in further decisions about pollution in populated areas.

Perhaps simply not drawing false conclusions from them would be better.

Exposure to air pollution seems to my intuition like it lowers a persons level of consciousness, and the lower a persons level of consciousness (the further down The Spiral Dynamics model they are) the more prone they are to violence.

Lead fucks people up. Always has, always will. Pretty easy to trace a relationship between lead concentrations and societal disfunction.

https://en.wikipedia.org/wiki/Lead%E2%80%93crime_hypothesis

So yes the incidence of cancer was higher in that area, but as soon as you controlled for population density, that effect disappeared.

Stuck with me as the 'most dangerous place' was a group of flats near the house I lived in at that time. I guessed it might be due to population density and was relived to find that was the case some time later.

I'd wager the ones with the pollution are going to eat each other's faces at a much higher rate than those without.

For giggles and to test some fall of Rome hypotheses, run a 3rd cage where the water comes through lead pipes.

This doesn't mean the future of science is in jeopardy. It just means more study is required and jumping to alter policy or make decisions based upon these studies, well, requires further study! :P

I don't understand why technical people waste their time complaining about this stuff. We all have the acumen to read, understand, and debate research.

Theory and speculation have a place in science.

Saying "no" to everything is no different than saying "yes" to everything from a logical perspective.

The typical "correlation doesn't imply causation" retort we see denialists level is a classic example of how people tend to use a phrase to avoid a reason-driven conversation about correlations (of which causal relationships are a subset) and instead shut down the entire topic.

The core of skepticism is inquiry, not denial. And modern Reactionary skepticism (because that is what it has evolved into now: a kind of reactionary culture clique) is all about stopping any inquiries it isn't predisposed to prefer.

I was warned off eating the food I grew in my garden in London as historically people threw their ash into their gardens, so the soil their can be pretty polluted.

You seem to be stickler for the rules, so I can’t understand your position on this.

Which is why this paper and most of the comments in this thread reek of falsities and unfounded bias. Which is the norm here now.

Hi dang.