Yes, lead poisoning could really be a cause of violent crime

[happyslug]

62. Lead paint, and the switch from lead pipe water systems after 1900, better reporting

Most water systems used lead prior to around 1900, Around 1860s a movement started to remove these lead pipe and replaced them with copper, but took 20 years to be implemented and even then it took years for the older lead systems to be replaced by copper.

Now large pipes, in the 1800s, were made of wood (and many are still in use, as long as they never dry out they last a long time), but when it came to pipes in homes, lead was the metal of choice prior to about 1860. My mother's house, built in 1917, still has lead pipe in it (long bypassed), but lead piping was still used in some applications as late as WWI for it was more flexible then copper.

In homes built prior to 1900 lead pipes still show up every so often, if not disturbed lead pipe can last a long time, but the problems with lead were known by 1860 and a movement started to get rid of lead water pipes at that time. Newer homes, built after 1900 for example, tended to have mostly copper piping, but some retain lead in certain locations. Lead pipes were not outlawed till after WWII, and then only in urban areas with building codes.

On top of this lead paint was big prior to the 1920s. but the effect of lead paint had become known by 1900, so that after WWI an international movement occurred to ban such paint. While the US was the only significant manufacturing nation to oppose the ban before, during and after WWI, several paint companies refused to produce lead base paint (For example Pittsburgh Paint, a dominate paint in commercial settings, was known for its non-lead base paint from its purchased by PPG corporation in 1898 and its change of name to Pittsburgh Paint). Most professional painters use Pittsburgh Paints due to its ease of application, its ability to cover other paints even at the cost of the paint being two to three times the price of other paints).

Between the drop in the use of lead in water systems (mostly in the main lines to homes as while as in homes) and the reduction in the use of lead paint after 1900 (Except in industrial settings) would explain the drop in crime in the 1920s. Increase urbanization (movement from the country to the city) which tended to move people into older tenements (With its lead water systems and lead paint) in the 1920s would also explain the increase in crime in the 1930s.

Side note: The FBI keeps National Crime reports today, but it is a compilation of reports given to local police. When surveys are done about crime, the FBI statistics are viewed as unreported except in the case of murder. Furthermore the FBI only started to do such reports in 1930 (and only officially issued the reports from 1935), thus the drop in Crime in the 1920s and increase in crime in the 1930s may just be the effect of someone actually collecting the data. I.e. Data prior to 1935 could and was missed, even for murder, if a local police department decided NOT to file a report. To a degree you have that problem to this very day, but almost all Police department have sent in the data since 1935,

Another problems with records before the 1920s, is that the 1920 Census was the first Census to show more people living in Urban Areas (including Urban Clusters like small towns) then in Rural Areas. Given that Rural Areas, even today, tend to be patrolled by State Police agencies instead of local police, the History of the Nation's State Police is a factor. Pennsylvania adopted the First State Police in the US in 1903, but it was more a labor control mechanism then anything else (The Texas Rangers existed prior to that date, but was more a pseudo-military organization till it was reformed into its present form in 1935).

In the 1920s a new type of State Police come into being, paid by giving tickets to motorists, these were called "Highway Patrols" for that was their duty, to patrol the highways of the state so that the then new state laws governing automobile use was followed. Pennsylvania even adopted one in 1927 (Yes, Pennsylvania had TWO state police forces from 1927 till the late 1930s when the two forces were merged into the "Pennsylvania Motor Police" which changed its name to "Pennsylvania State Police" in 1948).

Other states also adopted State Police Forces or Highway Patrols in the 1920s and 1930s. Most followed the example of the Pennsylvania Highway Patrol, paid by giving tickets, but also providing police services on Rural Highways. As a side factors, such Highway Patrols/State Police forces started to investigate other crimes reported to them outside the jurisdiction of any local police (Which were restricted to urban and suburban areas of the State). By the mid 1930s, you finally had Police Forces governing almost all of the US, something that was NOT the rule 20 years before. In 1915 if a murder occurred in a rural area, it was handled by the County District Attorney or Prosecutor but not the Police for no police existed in that area. This was due to the fact that there was no police force in most of rural America to report the murder from to any national data base. By the mid 1930s that had changed, with the widespread adoption of State Police/Highway Patrols you finally had Police covering Rural Areas of the US and thus a Police Department to report the murder to, and thus a Police Department to send data of crime to the FBI in Washington.

In simple terms, the increase in crime the 1930s may be the result be better reporting of crime. This is especially a factor for the South was and is the most populated rural area of the US (The Rocky Mountain west is larger, but has much lower population compared to the rural South). The South, even in colonial days, were know to be much more violent then the rest of the US. The rural South retain that elevated level of violence, compared to the rest of the nation, to this day (Through it has declined over the last 50 or more years). This violence is more related to who and how the South was settled, then lead, but lead would still be a factor for lead would have made a bad situation worse (and they is some evidence it did).

On the other hand, the South would have had the worse ability to record crime rate in the country until the adoption of State Police forces in the 1920s and 1930s. Thus the increase in crime in the 1930s, may just be the result of the Rural South Finally reporting its crimes to a national data base, thus increasing the crime rate tremendously.

Just a comment that when it comes to crime rates in the US, any statistics prior to WWII is questionable. There was NO law to report such crimes to a central data base and most of the US (in area) did not even have the organization (Police) to gather and send the data to a national data base (The FBi authorized to do so in 1930, did not issue a report till 1935).