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Lead in Drinking WaterSTARTING IN EARLY 2015, Flint, Michigan entered the news spotlight for having high levels of lead, a toxic substance, in the drinking water provided by the city. Flint pediatrician, Dr. Mona Hanna-Attisha, found that the proportion of infants and children with elevated levels of lead in their blood nearly doubled after the city switched to a new water source.

Infants and young children face well-known dangers when exposed to lead. Even at low levels, lead exposure in early development aff ects brain development and leads to problems with learning and behavior. These brain eff fects appear to be permanent.

The Centers for Disease Control lists the two biggests sources of environmental lead contamination as lead-based paint in homes built before the 1970’s and lead in soil from use of gasoline with a lead additive to boost performance. (Leaded gas was outlawed in the U.S. after 1996.) The Flint situation has drawn media attention to drinking water as a source of environmental lead. The USA Today news network reviewed EPA data and reported that since 2012, nearly 2,000 water systems across the U.S. have had elevated lead levels in tap water samples.

How much lead is harmful?As scientists have learned more about the eff ects of lead on the developing brains of children, ideas about how much lead is harmful have changed. In May 2012, the U.S. Centers for Disease Control and Prevention (CDC) announced that 5 micrograms per deciliter (µg/dL) is now the level of lead

at which notifi cation of parents and follow-up actions, including eliminating sources of lead in the child’s

environment, are recommended. This new level is half the previous level of 10 µg/dL. The graph above shows

how the level of lead considered harmful to children has changed

since 1960.

Why is lead toxic?Lead is toxic because it is very similar to another metal —calcium— that is essential for many important cell functions. You may have been told to drink or eat calcium-rich foods for strong bones and teeth, which is certainly important, but calcium does much, much more.

BONE

NEURONS

MUSCLE

BLOOD

Once lead enters your body through ingestion (eating or drinking) or inhalation (breathing), cells absorb lead in the same way that they absorb calcium. Once in cells, lead interferes with normal cell functions that depend on calcium.

The many jobs of calcium

• Calcium is involved in the coagulation of blood.

• Calcium is essential for muscle contraction.

• Calcium helps maintain normal blood pressure.

• The fl ow of calcium ions between nerve cells is essential for brain development and function.

• Calcium is the main component of bones and teeth.

1960 – 1970 1970 – 1985 1985 – 1991 1991 – 2012 2012 – present

Blood lead levels considered harmful to childrenBlood lead level (µg/dl)

60

30 25

10 5

+

2Lead in Drinking Water

How does lead get into water?Have you ever gone fi shing? You might have tied a small piece of lead metal called a sinker to the fi shing line to help it sink into the water. A lead sinker would be pretty useless if it dissolved in water! The same goes for plumbing pipes made of copper, iron, or lead metal. These pipes couldn’t carry water if the metal dissolved in water!

So…if these metals don’t dissolve in water, how does lead get into drinking water? The answer depends on the diff erence between copper, iron, or lead atoms and copper, iron, or lead ions. Atoms of copper, iron, or lead rarely go into water, but ions of these metals do.

An atom becomes an ion through a chemical reaction. In the reaction, negative particles (electrons) are lost by one atom or ion and gained by another atom or ion. For example, metal atoms of copper, iron, or lead can lose electrons to O

2 (oxygen), Cl

2 (chlorine), or H+

(hydrogen ion).

The pictures below show how lead atoms from a pipe can become ions and get into the water. A substance is called “corrosive” when it breaks down metal through a chemical reaction. In the example below, vinegar is the corrosive material. In the case of Flint, Michigan, chlorine was a corrosive material in the water that caused lead ions to form and enter the water.

Pb Pb

Pb Pb

Pb Pb

Pb Pb

Pb Pb

Pb Pb

solid lead pipe

H

HO

H

H

O

HH

O

HHO

H+

H+

–OAC

–OAC

HOAC

HOAC

solid lead pipe

BEFORE

HOAC = vinegar (Vinegar is slightly corrosive.)

Some HOAC is present as H+ + –OAC

water �owing through lead

pipe

Pb Pb

Pb Pb

Pb Pb

solid lead pipe

Pb Pb

Pb Pb

Pb

solid lead pipe

Pb2+

H

H O

H

H

O

HH

O

HHO

–OAC

–OAC

H—H

H—Hrepresents hydrogen gas about to �oat away

HOAC

HOAC

AFTER

water �owing through lead

pipe

You’ve probably seen what happens when iron metal loses electrons to oxygen. This chemical reaction forms that orange � aky stu� that we don’t want to see on our cars. Yes, rust! Rust is a compound made of iron ions joined to oxygen ions.

The “BEFORE” picture shows a lead metal pipe containing neutral atoms (Pb) with water (H-O-H) and vinegar (HOAC) molecules fl owing through it. Some of the vinegar is separated into ions (H+ and OAC–).

The “AFTER” picture shows that an atom of lead has lost two electrons, is now an ion (Pb2+), and has left the metal pipe and entered the water. The hydrogen ions gained the two electrons from the lead and joined together to form hydrogen gas (H-H).

3 Lead in Drinking Water

Why can lead mimic calcium? Lead can mimic calcium in cells because lead and calcium are both metals that readily form an ion with a charge of 2+.

A 2+ charge means that the calcium ion is missing two of the electrons found in the calcium atom. The charge of an ion is an important factor in its interactions with other ions and compounds.

The 2+ charge allows calcium ion to form a connection or “bridge” between two other ions or compounds. In bones and teeth, this calcium bridging forms a very hard mineral called hydroxyapatite. This bridging capability also allows calcium ion to be involved in transferring nerve signals, helping muscles move, and maintain blood pressure and coagulation.

Because they have the same 2+ charge, lead ions enter the body in the same way as calcium ions. Lead ions can substitute for calcium ions in bones, nerves, and muscles, but once in place, they don’t work exactly the same way. For example, lead ions do not correctly transfer nerve signals the way calcium ions do.

calcium atom (Ca) calcium ion (Ca2+)

Ca Ca

2+

Ca Ca

2+

lead atom (Pb) lead ion (Pb2+)

Pb Pb

2+

Pb Pb

2+

Can we test for metals in liquids?We’ve just discussed the ability of 2+ calcium ions to form connections or bridges between compounds. Other 2+ metal ions can form these connections. Another name for this process is crosslinking.

We can use a material called sodium alginate to test whether 2+ metal ions are in a liquid. Sodium alginate is made up of long strands of a natural polymer from seaweed with sodium ions attached. When dissolved in water, these strands fl ow freely around each other. If we add sodium alginate to water containing calcium 2+ ions, the calcium ions replace the sodium ions and form crosslinks between the polymer strands. The sodium alginate is now calcium alginate, and instead of fl owing freely, calcium alginate is a thick, gooey gel. Other 2+ metal ions also crosslink with alginate. Adding sodium alginate to liquids containing 2+ ions of copper, iron, or lead results in the the alginate forming a gel. So, the formation of gel is a positive test for the presence of these metal ions. If we add the sodium alginate slowly in drops, rather than stirring it in, the crosslinking process produces small gel balls.

Na+

Na+

Na+

Na+

Na+

Na+

Na+Na+

Na+Na+

Na+

Na+Na+

Na+

Ca2+

Ca2+

Ca2+

Ca2+

Ca2+

Ca2+ Ca2+

sodium alginate dissolved in water calcium alginate is a geladd calcium chloride solution

Ca2+

Alginate’s gelling property makes it a good food thickener, helping products such as pudding, ice cream, and sauces become thicker and feel more creamy in customers’ mouths.

In its elemental form, calcium is a metal found in group 2A on the periodic table. Calcium metal reacts with water to form calcium 2+ ion and hydrogen gas. In our bodies, which contain a lot of water, calcium couldn’t exist as a metal, and is present in the form of calcium 2+ ions. Ions dissolve in water because water is polar.

4Lead in Drinking Water

Good nutrition to battleenvironmental toxicants.

Developed by

through funding from

Grant number R25 OD011090

Fighting the e� ects of lead exposureAvoiding exposure to lead, especially for young children, is always the goal, but in environments with more risk of lead exposure, food choices can actually help fi ght the eff ects!

Dr. Mona Hanna-Attisha, the Flint, Michigan pediatrician who reported on elevated blood lead levels in local children, has recommended that local families focus on diets rich in calcium, iron, and vitamin C. Here’s why eating these foods helps:

Absorb less lead: Before something we ingest gets into our bloodstream and cells, it must be absorbed by the digestive system. Scientifi c research shows that increased intake of calcium and iron decreases the absorption of lead by the digestive system. So, even if you are exposed to lead and possibly ingesting it, getting enough calcium and iron means less lead will be absorbed. The vitamin C keeps iron in the +2 ion form where it is better absorbed by the body.

Bethany Thayer, director for the Center for Health Promotion and Disease Prevention at Henry Ford Health System, supports the role of diet, but adds that just having food in your stomach will decrease the absorption of the lead. She recommends that children at risk of lead exposure eat more frequent but smaller meals throughout the day.

Release less lead: The process of bone remodeling releases calcium into the blood. If the bones contain lead, lead is released at the same time. Getting enough calcium in the diet reduces the amount of calcium your body needs to get from bones. If less bone remodeling is needed to provide calcium, less lead is released. Nutrition is especially important in periods of stress or during pregnancy, when more calcium is released from bone.

Bone — An accidental lead bankBecause of its ability to mimic calcium, some of the lead that enters the body ends up being stored in the bones along with calcium. Medical researchers studying the accumulation of lead in bones sometimes use radiographs (pictures made with X-rays) to view bone lead content.

One of the functions of bone is to provide a storehouse of calcium ions. The hardness of bone might lead you to think it never changes. But bone actually breaks down and rebuilds throughout life in a process called remodeling. During remodeling, calcium ions are constantly leaving dying bone cells, circulating in the blood, and then becoming part of new bone cells.

If bones also contain lead, the lead ions can leave the bones and circulate in the blood just like calcium. When the lead circulates, it can cause problems with cell functions that involve calcium. Because of this “lead bank,” lead can continue to aff ect the body years past the original exposure.

This x-ray shows the knee of a three-year-old girl with a blood lead level of 10.6 µg/dL. The lighter areas show lead accumulation.

The Hurley Medical Center in Flint, MI has created a “Nutrition and Lead” recipe guide. One of the recipes, called Cheesy Hamburger Skillet, includes bell peppers, tomatoes, cheese, and beef. One serving provides a child 1–3 years old with these percentages of the recommeded daily amounts:

• 21% calcium • 24% iron • 386% vitamin C