Trace Elements at LLSG Lead (Pb)

Atomic Number:	82
Atomic Symbol:	Pb
Atomic Weight:	207.2
Electron Configuration:	[Xe]6s²4f¹⁴5d¹⁰6p²

TITLE

Lead (Pb)

SYNONYMS/FORMS

Plumbum, lead (IV) hydride

GENERAL INFORMATION

Lead poisoning is one of the most common environmental health problems today, especially in children. Lead can severely damage all parts of the body. The most sensitive organ is the central nervous system, particularly in children. Even short term exposure can cause developmental delays in children (1, 2).
Lead will affect many enzymes systems; those involving ligands with sulfhydryl groups are especially vulnerable. The best-known effect is inhibiting heme production and causing anemia (3). Lead also damages the GI trace, kidneys and the reproductive system. The effects are the same whether it is breathed or swallowed.
Lead is eliminated from the body mainly through the kidneys. Half-life in blood is 30 days, and in bone 20-30 years (3). Lead absorbed in childhood accumulates in bone. Years later, lead stored in bone may be released into blood during pregnancy. Lead can cross the placenta and affect the fetus.

SOURCES/ROUTE OF EXPOSURE

Occupational Exposure:
Lead mining and refining, smelters, welders, glassmakers, scrap metal workers, lead battery manufacturing and recycling, plastic manufacturing, auto repair, and construction work. Lead workers can carry lead back home on hands, clothes and hair, exposing family members.
Non-occupational Exposure:

Drinking water, due to lead solder in water pipes
Paints, dust and soil
Plastic window blinds, ceramic ware, solder in tin cans
Food - plants that absorb lead from air
Asian or Hispanic folk remedies contain high concentration of lead
Hobbies such as pottery, stained glass, preparing lead shot or fishing sinkers
Houses built before 1978 may have lead-based paints, especially those built 1920 -1950.

TOXICITY

Short-term Exposure:
Vomiting, diarrhea, convulsions, coma or even death. Severe cases of lead poisoning are rare in Canada.
Long-term Exposure:
Damage to the nervous system causing impaired mental function, anemia, loss of appetite, abdominal pain, constipation, fatigue, sleeplessness, irritability and headache. Continued excessive exposure, as in an industrial setting, can affect renal and reproductive systems.
No specific group-of symptoms exist. Consider lead poisoning whenever peculiar symptoms that do not match any one particular disease develop, especially in small children. These may include, irritability, excess lethargy, poor appetite, abdominal pain with or without vomiting (without diarrhea), and headaches

MONITORING/CLINICAL INTERPRETATION

Screening of Children
The CDC guidelines recommend universal screening for virtually all young children, maximizing screening of children at high-risk and reducing screening of children and low-risk (4). Children living in the old houses (built before 1950) are at high risk of lead exposure due to the lead paint and should be screened with a blood lead test.

No lead levels in children are deemed safe. In 1991 the CDC defined the blood lead level of 0.48 umol/L (10 ug/dL) was the threshold. However, accumulated evidence shows that blood lead levels greater than 0.12 umol/L (2.5 ug/dL) can affect a child's cognitive skills (5,6). Recently, we established the pediatric reference range for blood lead as <0.10 umol/L (0-16 years old) and defined the alert value and action value as follows:

Whole Blood
Alert Value for Children: >0.12 umol/L
Action Value for Children: >0.48 umol/L
Action Value for Adults: >1.00 umol/L

Erythrocytes
Alert Value for Children: >0.26 umol/L
Action Value for Children: >1.06 umol/L
Action Value for Adults: >2.2 umol/L

Recommend actions to be taken according to Blood lead level (7)

Whole Blood Lead (umol/L)	Action
0.30 - <0.50	Above average in Canadian population: take exposure history
0.50 - 0.75	Repeat blood test now and in 3-6 months; locate source to reduce exposure
>0.75 - 1.00	Refer patient to a pediatrician for lead poisoning assessment
>1.00 - 2.10	Refer patient to a pediatrician immediately. Chelation considered
>2.10	Urgent case management: hospital admission

Recommend actions to be taken according to lead level
Erythrocyte

Lead (umol/L)	Action
0.66 - <1.10	Above average in Canadian population: take exposure history
1.10 - 1.65	Repeat blood test now and in 3-6 months; locate source to reduce exposure
>1.65 - 2.20	Refer patient to a pediatrician for lead poisoning assessment
>2.20 - 4.62	Refer patient to a pediatrician immediately. Chelation considered
>4.62	Urgent case management: hospital admission

Biological Monitoring of Lead Workers

Biological Exposure Index (8)
Lead in Blood: 30 ug/100 mL (1.45 umol/L)

The aim of blood lead monitoring of workers exposed to lead is to maintain a whole blood lead level below 1.5 µmol/L.
A pre-employment screen is recommended to exclude sources of lead other than occupational exposure.

The Occupational Safety and Health Administration (OSHA) has published standards for employees working in industry. Employees with whole blood lead >2.41 umol/L (50 ug/dL) averaged over six months must be removed from workplace exposure (9).

MATRIX CHOICE

Whole blood lead is the best screening and diagnostic test for lead poisoning. It is commonly used for industrial and environmental monitoring (for both acute and chronic exposure).
Erythrocyte lead is a very sensitive marker of lead exposure since over 93% of the lead is bound to hemoglobin in the blood.
Urine, random or 24-h, is commonly used for occupational monitoring.
Hair lead may be used for chronic exposure. However, it is difficult to distinguish whether the lead being measured is from endogenous or exogenous sources, such as from hair treatment products, strong alcohol intake, and tobacco smoke (10) or exposure from the workplace such as the plastics industry and plumbers working with lead solder.

TREATMENT

1. Remove from source of exposure.
2. Chelation therapy with ethylenediaminetetraacetic acid (EDTA).

Precautions: Chelation is not specific to lead and may reduce levels of other trace elements within the body.

REFERENCES

1. http://www.nlm.nih.gov/medlineplus/leadpoisoning.html
2. Effects of lead on human health. http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/environ/lead-plomb-eng.php
3. Toxicity, Lead. http://emedicine.medscape.com/article/815399-overview
4. Preventing lead poisoning in young children. Atlanta, GA: US Department of Health and Human Services, 1991.
5. Canfield RL, et al. N Eng J Med 2003;348:1517-1526.
6. Lanphear BP, et al. Public Health Report 2000;115:521529
7. Sanborn MD et al. CMAJ 2002; 166:1287-1292
8. ACGHI (American Conference of Governmental Industrial Hygienists). Threshold Limit Values for Chemical Substances andPhysical Agents & Biological Exposure Indices, 2008
9. OSHA Lead Standard - Requirements from the General Industry Standards Lead. http://www.osha.gov/SLTC/lead/standards.html
10. Strumylaite, L, et al.. Content of lead in human hair from people with various exposure levels in Lithuania. Int. J. Hyg. and Environ Health, 2004; 207:345-351

TEST INFORMATION/
REFERENCE RANGES


January 31, 2012