lead in new buildings: unc chapel hill marc edwards

Lead in New Buildings:Lead in New Buildings:UNC CHAPEL HILLUNC CHAPEL HILL

Marc EdwardsMarc Edwards

Background: Lead in New Buildings.Background: Lead in New Buildings.

Preliminary Findings on Lead at UNCPreliminary Findings on Lead at UNC– Focus on the worst samplesFocus on the worst samples– How bad is/was the problem?How bad is/was the problem?

Mitigating the Problem:Mitigating the Problem:– Short-term: Short-term: Minimizing Minimizing

Exposure/FlushingExposure/Flushing– Intermediate-term: Fine-tuning the Intermediate-term: Fine-tuning the

ChemistryChemistry– Longer-term: Changing the Plumbing Longer-term: Changing the Plumbing

CodeCode

The Cause of the ProblemThe Cause of the Problem“Lead Free” Brass“Lead Free” Brass

1986 Safe Drinking Water Act 1986 Safe Drinking Water Act Lead Lead BanBan– Pipes and solders < 0.2% lead by weightPipes and solders < 0.2% lead by weight– Brass < 8% lead by weightBrass < 8% lead by weight

Lead free brass can legally Lead free brass can legally containcontain

up to 8% lead by weightup to 8% lead by weight

Also pumps, valves, water meters, backflow preventors, etc.

Why Leaded Brass in Why Leaded Brass in the First Place?the First Place?

Pb (up to 8% by weight) Pb (up to 8% by weight) addedadded to to brass in order to:brass in order to:– seal leaksseal leaks– improve corrosion resistanceimprove corrosion resistance– ease machining of intricate brass ease machining of intricate brass

devicesdevices

Most modern brass products contain < 3% Pb

Other informationOther information

Higher purity waters (lower alkalinity, Higher purity waters (lower alkalinity, etc) more likely to leach lead from etc) more likely to leach lead from brassbrass

Rainwater and distilled water Rainwater and distilled water extremely aggressiveextremely aggressive

Water at UNC is very pureWater at UNC is very pure Corrosivity mostly countered by Corrosivity mostly countered by

raising pH and adding inhibitorraising pH and adding inhibitor

In most cases In most cases lead leaching lead leaching

from brass from brass drops off with drops off with

age…age…

0

10

20

30

40

3 4 5 10 11 12 17 18 19

Sampling Day #

Pb

(p

pb

)

LCR Action Level: 15 ppb

Test Water

But some waters But some waters are more are more

aggressive to aggressive to brass, and cause brass, and cause lead leaching to lead leaching to rise for a time rise for a time before falling…before falling…

10x

Lower pH-Lower Alkalinity Water more aggressive

0

10

20

30

40

3 4 5 10 11 12 17 18 19

Sampling Day #

Pb

(p

pb

)

LCR Action Level: 15 ppb

Low Alkalinity-Low pH Water

NSF Test Water

UNC LEAD PROBLEMUNC LEAD PROBLEM

UNIVERSITY WAS VERY AGGRESSIVE IN UNIVERSITY WAS VERY AGGRESSIVE IN SEEKING OUT “WORST CASE” SAMPLESSEEKING OUT “WORST CASE” SAMPLES– Removed brass plug to sample water from Removed brass plug to sample water from

backflow preventorbackflow preventor– Removed aerators to sample faucetsRemoved aerators to sample faucets– Sampled hot waterSampled hot water

MANY SAMPLES COLLECTED WITH MANY SAMPLES COLLECTED WITH ALARMING LEVELS OF LEAD (> 500 ALARMING LEVELS OF LEAD (> 500

ppb)ppb)

No alarming lead values came from No alarming lead values came from appropriate samples of drinking appropriate samples of drinking

water….water….

Removing brass plugs and aerators before Removing brass plugs and aerators before sampling, creates metal “turnings,” essentially sampling, creates metal “turnings,” essentially adding fine pieces of brass to samples and giving adding fine pieces of brass to samples and giving high lead valueshigh lead values

Lead values in recent sampling using conventional Lead values in recent sampling using conventional approaches indicates a significant, lower level lead approaches indicates a significant, lower level lead problem, consistent with brass in new builds problem, consistent with brass in new builds

““Beres” SamplesBeres” Samples   6 samples collected afternoon of 2/13/076 samples collected afternoon of 2/13/07 Caudill Labs floors G, 1 and 3 specifically Caudill Labs floors G, 1 and 3 specifically

the Men's restroom faucets and the the Men's restroom faucets and the drinking fountains in the SW corridordrinking fountains in the SW corridor

No building flushing at the time and No building flushing at the time and representative of water people were representative of water people were drinking (but not first draw)drinking (but not first draw)

5 of 6 samples tested:5 of 6 samples tested:Highest lead was 3.3 ppbHighest lead was 3.3 ppb

““Beres” Samples (Cont’d)Beres” Samples (Cont’d)

  143 – 313 ppb Cu143 – 313 ppb Cu 25 - 270 ppb Zn25 - 270 ppb Zn

Evaluation of Copper Speciation and Water Quality Factors That Affect Aqueous Copper Tasting Response Jonathan D. Cuppett, Susan E. Duncan and Andrea M. DietrichChemical Senses 2006 31(7):689-697; doi:10.1093/chemse/bjl010

Group taste threshold for Group taste threshold for CuCu+2+2 = 400 ppb = 400 ppb

The lower level lead problem The lower level lead problem has responded well to flushing has responded well to flushing

and cleaning of aeratorsand cleaning of aerators

Building pipes were not thoroughly Building pipes were not thoroughly cleaned with aerators off when cleaned with aerators off when commissioned, or if it was cleaned, it commissioned, or if it was cleaned, it was not successfulwas not successful

Flushing drops lead by removing Flushing drops lead by removing sediments and hastening formation sediments and hastening formation of protective film on brassof protective film on brass

CAUSE OF THE LOW CAUSE OF THE LOW LEVEL LEAD LEVEL LEAD PROBLEMPROBLEM

8.0 x 10-3 in2/mL

Meringue dezincificationMeringue dezincification

> pH 8.2> pH 8.2 High Ratio High Ratio

– ClCl--:HCO:HCO33--

Hot WaterHot Water

Zinc enriched scale forming in brass from home with complaint elsewhere in water system

Turner DiagramTurner Diagram

(15 mg/L hardness, 14 mg/L Cl-)

OWASA Lead StudyOWASA Lead Study(12 waters x triplicate (12 waters x triplicate

conditions)conditions)

PreliminaryPreliminary Trends Trends

(OWASA RESEARCH)(OWASA RESEARCH)

0

2

4

6

8

10

12

14

16

18

pH 8.3, 0.2 PP pH 7.7, 0.2 PP pH 7.7, 0.5 Zn o-P

Le

ad

(p

pb

)

t = 6 daysUnusual problem canget betterat lower pH!

LegislationLegislation

Lead Free Drinking Water ActLead Free Drinking Water Act– Would reduce allowable lead to 0.25%Would reduce allowable lead to 0.25%– Reintroduced a few weeks agoReintroduced a few weeks ago

CA Assembly Bill 1953CA Assembly Bill 1953– Limits the amount of lead in brass at Limits the amount of lead in brass at

wetted surfaces to < 0.25%wetted surfaces to < 0.25%

AcknowledgementsAcknowledgements

UNC AdministrationUNC Administration OWASAOWASA