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Lead poisoning

د.سجال فاضل فرهود الجبوري

METAL TOXICITY

Lead poisoning

Saturnism, plumbism))

Is a medical condition caused by increased levels of the metal lead in the blood .Lead may cause irreversible neurological damage as well as renal diseases ,cardiovascular  effects, and   reproductive toxicity.

INTRODUCTION

Humans have been mining and using this heavy metal for thousands of years, poisoning themselves in the process due to accumulation and exposure. These dangers have long been known, though the modern understanding of their full extent and the small amount of lead necessary to produce them is relatively recent; blood lead levels once considered safe are now considered hazardous, with no known threshold. Lead has also been found in some pool paint - especially those painted by lead-based epoxy paint

Today, most exposure in developed countries is the result of occupational hazards ,leaded paint and leaded gasoline (which continues to be phased out in most countries). Lead poisoning interferes with the normal development of the brain.

Hazard:

    1-inhalation: is the predominant hazard (dust ,fume).

    2-intact skin :organic compounds are absorbed through intact skin.

    Ingestion: mostly environmental. are rarely occupational.

Signs and symptoms:

Symptom of acute poisoning:

Abdominal pain

Constipation

Vomiting

Metallic taste in the mouth

headache

Chronic poisoning:

Peripheral neuropathy rare now) wrist drop.

Sign of anemia

Blue line on the gum due to deposition of lead sulfide in the gingival margin.

Encephalopathy mostly in children&

&rare in adult but still serious complication

HAEMATOLOGICAL FINDINGS

Blood film examination may reveal basophilic stippling of RBC as well as the changes normally associated with iron-deficiency anemia

(microcytosis and hypochromasia). However, basophillic stippling is also seen in unrelated conditions, such as megaloblastic anemia.

MECHANISM OF

TOXICITY

1-Lead  interferes with an essential enzyme delta-aminolevulinic acid dehydratase ,  which is important in the biosynthesis of heme ,the cofactor found in hemoglobin.

 2- inhibits the enzyme ferrochelatase, which catalyzes the joining of protoporphyrin IX and Fe2+ to form heme.

LEAD AS AN

 OCCUPATIONAL HAZARD

1- Lead-related industries such as lead smelting, refining, and manufacturing industries.

2-Home renovation that involves scraping, remodeling, or otherwise disturbing lead-based paint.

3-Hobbies and activities where lead is used.

4- Workers may inhale lead dust and lead oxide fumes, as well as eat, drink, and smoke in or near contaminated areas, thereby increasing their probability of lead ingestion.

SOURCE OF LEAD TOXICITY:

1- children under 12: The main sources of poisoning is from ingestion of lead contaminated soil.

2- ingestion of lead dust or chips from deteriorating lead-based paints.

 This is particularly a problem in older houses where the sweet-tasting lead paint is likely to chip, but deteriorating lead-based paint can also powder and be inhaled.

 3- drinking water. It can come from plumbing and fixtures that are either made of lead or have trace amounts of lead in them.

4-Ingestion of metallic lead, such as small lead objects, will lead to an increase in blood lead levels, and possibly death

5-kohl from the Middle East, India, Pakistan.

6- toys, such as many made in China.

7- folk remedies like Azarcon which contains 95 percent lead.

8-china, dishes, and mugs

LAB TECHNIQUES

1-BLOOD LEAD LEVEL(BLL) ), in (?g/dL).  10 ?g/dL or above is a cause for concern. However, lead can impair development even at BLLs below 10 ?g/dL.

2- Lead in teeth or bones can be measured by X-ray

3-ERYTHROCYTE PROTOPORPHYRIN (EP) increases when the amount of lead in the blood is high.

 The average person has less than 10 microgram per deciliter  or 100 part per billion ppb, of lead in their blood. People who have been exposed to an unusual amount of lead will have blood lead levels higher than 200 ppb—most clinical symptoms of lead poisoning begin at around 100 ppb. The effect on children s mental/cognitive abilities has been noted at very low levels.

                                            TREATMENT

Although the most important part of treating lead poisoning is decreasing exposure to lead, there are some forms of chelation therapy that can be used to reduce existing BLL levels:

DMSA
EDTA
British anti-lewsite

MERCURY POISONING

 mercurialism is a disease caused by exposure to mercury or its compounds. Mercury (chemical symbol Hg) is a heavy metal which occurs in several forms, 1-metalic mercury

2-inorganicmrecury 

3-organic mercury

                                                                                                                                      Hazard of use: Mainly inhalation since Hg evaporated at room temperature

    *80% of inhaled mercury vapor absorbed from the lung, the rate of absorption depend on (particle size& chemical composition).

SIGNS AND SYMPTOMS

 ACUTE POISONING:

Is rare with acute febrile illness few hour after     exposure,cough,dyspnea,tachypnea,,Nausea,vomitting,lethargy,feeling of tightness in the chest,rigor,cyanosis,it resolve spontaneously in mild cases,

                                                                                                                                                                                                                                                                                                          Severe cases: admission to hospital &treatment on respirator.                                                                                                                                                                                                                                       

Chronic poisoning:

    1-Nervous system

    2-kidney

    *Early symptom are vague, dyspepsia &headache, excessive salivation, teeth become loose &drop out,mercury line on gum (dark brown), irretant dermatitis &discrete ulcer (powder holes),

    psychiatric symptoms(inorganic poisoning)

    Neurological symptoms(organic poisoning)

    Tremor is the characteristic disturbance in chronic poisoning (hatter shakes).

    Motor &sensory disorder,(spastic gaithyperactive tendon reflex, sensory parasthesia)

    Erythrism :abnormal state of timidity and can present as neurosis irritability,apathy,headache

    *kidney: Nephrotic syndrome

SOURCES OF MERCURY POISONING:

                                           :                                                                  

 1-The consumption of fish is by far the most significant source of ingestion-related mercury exposure in humans.

2-Exposure to mercury can occur from breathing contaminated air.

3- from exposure to mercury vapor in mercury amalgam dental restorations.

4-improper use or disposal of mercury and mercury-containing objects, for example, after spills of elemental mercury or improper disposal of

Fluorescent light bulbs.

5-Human-generated sources such as coal plants emit approximately half of atmospheric mercury. An estimated two-thirds of human-generated mercury comes from stationary combustion, mostly of coal.

6-non ferrous metal production.

7- mercury production (mostly for batteries). also absorbed from unbroken skin

Mechanisms of toxicity:

1-CNS damage, endocrine system ,kidneys and other organs

and adversely affects the mouth, gums, and teeth.

2-Exposure over long periods  to mercury vapor  results in brain damage and ultimately death.

3- Mercury is toxic to fetuses and infants. It causes serious birth defects ( Minamata disease).

4-Mercury exposure in young children can have severe neurological consequences, preventing  formation of myelin.

5-There is some evidence that mercury poisoning may predispose to Young syndrome (men with low sperm count and bronchiectasis).

DIAGNOSIS;

Diagnosis of elemental or inorganic mercury poisoning involves

1- history of exposure

2- physical findings

3- elevated  blood mercury: concentrations are typically less than 6 ?g/L,

4- If the exposure is chronic, urine levels can be obtained; 24-hour collections are more reliable than spot collections. It is difficult or impossible to interpret urine samples of patients undergoing chelation therapy, as the therapy itself increases mercury levels in the samples.

5-Diagnosis of organic mercury poisoning differs in that whole-blood or hair analysis is more reliable than urinary mercury levels.

Treatment:

1- Removing the source of the mercury is crucial. Decontamination requires removal of clothes, washing skin with soap and water, and flushing the eyes with saline solution as needed.

2- Immediate CHELATION THERAPY for a patient showing symptoms of severe mercury poisoning.

3-Chelation therapy for acute inorganic mercury poisoning can be done with DMSA,2,3 dimercapto-1-propanesulfonic acid (DMPS), D-penicillamine (DPCN), or dimercaprol (BAL). DMSA is the most frequently used for severe methylmercury poisoning, as it is given orally, has fewer side effects, and has been found to be superior to BAL, DPCN, and DMPS.

THIOMERSAL:

A preservative that contains mercury, has been added to vaccines to prevent their deterioration since the 1930s. No adverse effects of thiomersal have ever been proven, although some allergic reactions have been noted. Its use in vaccines has been hypothesized to cause   autistic behaviors.