Lead Contamination in Drinking Water

Tim AlbaStephanie Chan

Deb DryerJason Faulkenberry

Dan FergusonEmily Levin

Miyoko Sasakura

November 6, 2009

Sources of lead•Water infiltration through lead contaminated soil

• Lead pipes or pipes containing lead (banned in the 1930’s)

•Lead solder (banned in 1986)

•Brass fixtures

Solubility Conditions

• Long stagnation times

• High temperatures

• Freshly exposed plumbing

• Low pH

• Low alkalinity

• Soft water

Water Soluble forms of Lead

• Cerussite (PbCO3)

• Hydrocerussite (Pb3(OH)2(CO3)2)

(hydrated form of lead)

Health Effects of Lead• Natural element in the Earth’s crust

• In US surface and ground water, lead levels range between 5 and 30 ug/L

• Xenobiotic to the human body

Lead can mimic zinc, iron, and calcium

• Normal Humans levels (1999 – 2002):

1.9 ug/dL for children 1 – 5 years

1.5 ug/dL for adults 20 – 59 years

d/L = deciliter = 100 mL

• For the general population:

The most common source of environmental exposure is ingestion of contaminated water.

Lead in drinking water accounts for 14-20% of lead exposure

Health Effects of Lead• Ingested lead is absorbed by the gut and delivered throughout the body via the

circulation system

Adults absorb 3 – 10%

Children absorb 40 -50%

• Lead has a ½ life of 27 days in blood and 30 years in bone

• The main storage site for lead:

Bones (main storage site)

Blood

Soft tissue

• Lead can cross the blood-brain barrier, the placenta, and can be present in breast milk

• Lead is toxic to the hematopoietc stem cells, the renal system, the reproductive system, the cardiovascular system, and the peripheral and central nervous systems.

Health Effects of LeadSymptoms of lead poisoning:

Abdominal pain

Joint pain

Myalgia

Anemia

Fatigue

Headache

Sleep disturbance

Irritability

Malaise

• Symptoms are generally non-specific

• Those exposed may be asymptomatic until blood lead levels are extremely high

The CDCs blood lead level threshold for lead poisoning:Children: > 10 ug/dLAdults: > 40 ug/dL

There is currently no effective way to remove lead from the blood under 30 ug/dL

Health Effects of LeadChildren are the main concern with environmental exposure of lead from

drinking water

Several studies have shown that blood lead levels < 5 ug/dL are associated with:

• Delinquent behavior

• Deficits in IQ

• Learning Disabilities

• Anti-social behavior

• Higher drop-out rates

Health Effects of Lead• A recent study (2003) showed that the relationship between the amount of lead exposure and IQ deficit is not linear

The initial dose in young children does the most damage

• Another study associated childhood lead exposure with region specific reductions in adult grey matter volume

Anterior cingulate cortex:

Executive function

Mood regulation

Decision making

Lead and Copper Rule

• Lead and Copper Rule (LCR) established in 1991

• Rule applies to Community Water Systems (CWSs) and Non-Transient, Non-Community Water Systems (NTNCWSs)– Monitoring at customer taps rather than at entry point

of distribution system– Maximum Contaminant Level Goal (MCLG)=0mg/L– Action Level (AL)=0.015mg/L

• Based upon 90th%-ile level of collected tap water samples—no more than 10% of samples collected from specific tap can be above AL

Monitoring

• Number of sample sites dependent upon distribution system size

• Can reduce the number of times sampling conducted by decreased occurrence of action level exceedance

Action Level

• Upon exceedance of AL– Implement Water Quality Parameter (WQP)

monitoring– Corrosion Control Treatment (CCT)– Source water monitoring/treatment– Public education

• Repeated exceedance of AL– Lead Service Line Replacement (LSLR)

Treatment

• pH and alkalinity control lead solubility– minimum lead release is at pH 9.8 and

alkalinity of 28 mg/L– by adjusting the pH to greater than 9,

plumosolvency is greatly reduced in alkalinities ranging from 10-80 mg/L

– lead leaching was found to be very sensitive to alkalinities less than 50 mg/L

– lead release was found to be insensitive to pH at alkalinities greater than 100 mg/L

Treatment, continued

• pH and alkalinity are easily adjusted by addition of:– lime (CaO)

– slaked lime (Ca(OH)2)

– caustics (NaOH, KOH)

– soda ash (Na2CO3)

Control

• Corrosion Control– Lead service lines– Lead-Tin Solder

• Anodic polarization predominates

– Brass (1 – 7% lead)• First flush predominates

– Natural Organic Matter• Pb2+ - NOM complexes and surface microcrystals

Control, continued

• Disinfection processes– Many treatment processes switching from Free

Chlorine to Chloramines to avoid “known” DBPs– Controversial due to production of “unknown” DBPs– Chloramine residual produces a lower ORP, and

hydrocerrucite controls the solid phase, which releases more lead

– Free chlorine has a higher ORP, a PbO2 controlling solid phase, and therefore less lead release than chloramines

– ORP is a function of pH

Mitigation

• Corrosion Inhibitors

• Passivated Pipes

• Avoid coupling of dissimilar metals

• Avoid grounding household electrical system to the plumbing system

• Replace pipes with Medium Density Polyethylene (MDPE)

• Fluoride control

Reduction in blood lead levels, 1988-2002

“Blood Lead Levels --- United States, 1992—2002.” MMWR: Morbidity and Morality Weekly Report 27 May 2005, 54(20): 513-516

Large water utilities: LCR in 1991 with AL at 15ppb

U.S. EPA 2005b, “Comparison of lead action level exceedances between 1992/93 and 2000/04.” Available: http://www.epa.gov/ogwdw000/lcrmr/pdfs/Comparison of Lead Action Levels.pdf [Accessed 3 Nov 2009]

Percent of Medium &Large Water Systems over Action Level (>15ppb)

U.S. EPA 2005c,“January 2005 Summary of Lead Action Level.” Available: http://www.epa.gov/ogwdw000/lcrmr/pdfs/summary_lcmr_sdwisfed_data.pdf [Accessed 3 Nov 2009]

Case Study (DCWASA)1/2

• District of Columbia Water and Sewer Authority (DCWASA)

• 500,000 customers , 135 million gallons/day to 130,000 locations

• Nov2002 switched to chloramines

• 90% of 6,170 HH >15ppb (LAL)

• Peak with 90% of HH >59ppb (2004)

Case Study (DCWASA)2/2

• DCWASA, EPA and DOH take immediate action

• 2004 Optimal Corrosion Control Treatment (OCCT) study suggests chloramines are to blame

• Released of previously stable lead from services lines and other materials

• Added orthophosphate a passivating agent

Case Study (Philadelphia Schools)

• 2001 study evaluated drinking water lvls in 292 public schools

• 124(42.5%) lvls not exceed action lvl (20ppb)• 28.7% lvls from 20-50 ppb• 11.6% lvls from 50-100ppb • 17.1% lvls of 100ppb or more• Source: service connectors, lead goosenecks,

lead joints or other materials containing lead

Conclusions

• Lead pipes have been used for plumbing systems since Ancient Rome

• Lead pipes are likely to remain in use for many years– Not feasible to replace all currently installed

lead materials– Expensive, impractical– Pipes and fixtures beyond service connection

responsibility of the homeowner

• Traditionally lead is controlled through management of water quality

• Co-compliance with increasingly stringent EPA regulations can cause unforseen corrosion problems

Questions?