Sources of Lead Exposure
Because the element lead has such useful properties it has been used in many items. This means that there are many ways that lead can enter our bodies. As the news media focus on topics that will attract attention to generate advertising revenue, the media do not accurately portray reality and when people get their information from the media, incorrect perceptions of risk and hazard result. Recent media coverage of Flint water has caused many people to regard water as the main source of lead exposure, causing larger sources of lead exposure to be ignored. Unfortunately, many people do not realize that their charming century old home still contains massive amounts of lead.
The human body treats lead as if it were calcium, meaning that lead in the bloodstream can be deposited in bone and teeth. Unfortunately, over a person’s lifetime the lead in the bone comes out back into the bloodstream when bone density is reduced during pregnancy or aging. The blood lead level of the fetus is the same as the blood lead level of the mother. Lead that entered the mother’s body when she was a child comes out of her bones to expose the fetus in the womb. In the human body, lead also behaves as if it were iron, so sometimes ends up in iron bearing molecules and structures such as hemoglobin red blood cells.
In a perfect world, there would be no home or apartment in the U.S. with lead paint, lead plumbing, lead tableware or lead contaminated soil. In a perfect world, no one would live downwind from a coal fired power plant emitting lead or have to breath leaded aviation fuel exhaust. In a perfect world there would be no school full of lead paint and lead plumbing. Unfortunately, the U.S. has a huge number of schools and homes with lead paint and with lead plumbing with yards with lead contaminated soil. Removing 100% of the lead from our dwellings would cost a fortune and the political will unfortunately does not exist to do so. Government policy has been to address the most concentrated sources of lead first and with time address the less concentrated sources. Over the decades tremendous progress has been made.
Toxins can enter human bodies by ingestion, inhalation, crossing the placenta and through the skin. Back in the 1950’s the definition of lead poisoned was much higher. People breathed in lead just by breathing the air due to the heavy use of leaded gasoline. People ingested lead when eating canned food, due to the use of lead solder releasing lead from the solder into the canned tuna, tomato soup, etc. People were exposed to lead from the use of lead pigment in house paint. Most of the rest of the world banned lead in house paint in the 1920’s, unfortunately the U.S. did not until 1978. An extremely unfortunate policy choice has been to give occupancy permits for lead based on massive quantities of lead paint merely being covered up by a coat of latex paint. Many people misinterpret this occupancy permit to mean that there is no lead on the building, instead of meaning that the lead is intact at the time of inspection. Given the behavior of multiple layers of lead paint, the residential lead paint does not remain intact for long.
First, the good news! It may not feel like it, but the severity of lead poisoning has been decreasing. Today fatalities due to lead poisoning are not common in the U.S., whereas in the 1950’s they were common. Remember, the fatalities in Flint were not due to lead exposure, but to Legionnaire’s disease acquired from inhaling the water droplets when water was run, such as in a shower. The news media greatly under-reported the role of Legionnaires disease with Flint. Families can take steps to reduce exposure to lead by avoiding dangerous choices, such as not removing lead paint with a blowtorch or scraping; these activities are dangerous. Over the last century blood lead levels have greatly decreased in the U.S., partly as an unintended consequence of urban smog efforts mandating catalytic converters, which are damaged by leaded gasoline. The motivation to using unleaded gasoline was originally to reduce urban smog, not to reduce the amount of lead that people breathed into their bodies. Additionally, the mandate to line food cans with plastic has greatly reduced the amount of lead going into food.
In general, lead pigment in paint from our dwelling is the most concentrated source of lead exposure. It is not necessary to eat a visible paint chip to get lead poisoned, a toddler with normal hand to mouth activity can get lead poisoned just from the ambient household dust on their fingers. Given the enormity of the housing lead pigment problem, for decades the U.S. has had a policy of slap a coat of lead free latex paint on top of the multiple layers of lead paint. It doesn’t take long before the multiple layers of paint start peeling, exposing the lead. Friction surfaces such as doors and windows that are opened and closed generate lead dust. The window wells between storm window and the interior window
Even ambient household dust in new housing in the St. Louis region can be rich in lead. There is an expression in the lead poisoning prevention community that urban areas wouldn’t need street lights if lead glowed in the dark, since our urban soils are so contaminated with lead. St. Louis soil got a “double whammy” because in addition to our soil being contaminated from decades of leaded gasoline use, there were multiple lead smelters in the city of St. Louis. Housing also is a source of soil lead, often lead paint chips scraped from a home went into the soil. Carpeting and rugs concentrate the lead bearing soil particles in a home, making it available for toddlers to ingest it with normal hand to mouth activity. There was a case in St. Louis where a child that lived in a new home was lead poisoned. The lead case worker eventually figured out that the child was lead poisoned from petting the family dog. The family dog spent time outside and loved to roll in the dirt. Just from the normal hand to mouth activity and petting the dog, the child was lead poisoned.
In general, people tend to underestimate lead intake from food. Lead can leach out from food containers into the food. Old dishes, imported dishes and old leaded crystal beverage containers contain lead that can leach into the food. Food grown in soil can take up the lead in the soil. Soils contain low levels of naturally occurring lead, but human activities have greatly increased the lead levels of soils. Commercial crops can be grown in soil with lead levels above natural background from the previous use of lead arsenate pesticides, which were commonly used before the development of DDT. Decades of use of leaded gasoline also contribute to lead that enters food crops directly from the soil. Building demolitions add lead to the soil. Old bottles of vintage wine have a lead foil seal covering the cork. The lead can react with the atmosphere, releasing powdery lead compounds which can end up in the wine glass if not wiped away before opening the bottle.
A perception exists that tap water is a more dangerous source of lead exposure than dwelling paint. In lead paint, lead is the major element. Lead in household water is generally present on the parts per billion level, thus it would be necessary to drink an awful lot of water to get the same amount of lead as from from lead dust from lead pigment. This is the chemical formula of a commonly used lead pigment (PbCO3)2•Pb(OH)2
In general, lead in tap water come from the plumbing associated with the residence. In many places the service line that connects the dwelling to the water main bringing water from the treatment plant is made of lead metal. Additionally, within the dwelling lead can be found in the plumbing fixtures, lead solder connecting copper pipes and in the galvanized pipes. The amount of lead that leaches out of the plumbing into the water depends on many factors. Natural river, lake and groundwater composition varies greatly by region depending on the local geology. Any St. Louis resident with a coffee maker knows that a calcium carbonate scale builds up on the heating element with hardly any use.
Lead sources can sometimes be “fingerprinted” that is, distinguished by looking at the relative proportions of the lead isotopes.
Further information can be found in these sources:
TED talk on multiple lead sources
Lead poisoning fatality of Sudanese immigrant Sunday A. video including lead isotope fingerprinting Forensic Files Season 11 Episode 4
Flint NOVA PBS documentary link
Lead isotopes in coal fly ash link
Conversion of drinking water lead level and blood lead level Table 1
Herculaneum MO case study lead isotope fingerprinting sources
Omaha lead smelter Superfund cleanup
Lead in tap water to blood lead level conversion Table 1