Occupational toxicology

Ass. Prof. Laith A. Alrudainy

MBChB, MSc, PhD

Lecture 2

Environmental toxicology

Lead Toxicity

Sources of lead

- Extraction process

- Lead-acid battery manufacture

- Ship breaking

- Car radiator repair

- Welding

- Paint manufacture or application

- Plumbing

- Petrol manufacture

- Plastics manufacture

Biological Fate

Once in blood stream, lead is primarily distributed among three compartments:

• Blood ( 1%).

• Soft tissues ( Kidney, bone marrow, liver, and brain).

• Hard tissue ( the bone and teeth - 95% of the total lead in the body).

Signs and Symptoms

• Acute Toxicity

– Abdominal Colic/ Constipation

– Anemia

Signs and Symptoms

• Chronic Toxicity:

– Joint Aches (Arthralgias)

– High Blood Pressure

– Chronic Renal Failure

– Increase spontaneous abortions . . . Lead can easily cross the placenta

– Mental retardation and behavioral problems in children

Laboratory Evaluation

• The best screening and diagnostic test for lead poisoning is a Blood Lead Level (BLL).

Treatment and Management

• A symptomatic patients with BLL below 25 µg/ dl -------- separation from the source of exposure.

• Patient with blood lead level of 45 µg/ dl or greater ------ chelating therapy immediately.

Treatment and Management

• Chelating Agents:

1) BAL (British Anti-Lewisite) or dimercaprol.

2) CaNa2 EDTA

3) DMSA or succimer.

• Mechanism: Binds and removes inorganic lead from the soft tissues and bones.

Mercury Toxicity

Types of Mercury

• Three Types of Mercury:1) Elemental Mercury

2) Inorganic Mercury

3) Organic Mercury

Sources of mercury

1) Mining Operations

2) Paper Production

3) Medical Instruments:

Thermometer, Blood Pressure Apparatus

4) Dental Fillings:

Amalgams: 50% Mercury with Silver

Health Effects

• Elemental Mercury (mercury vapor):

• Lungs ----- Chemical Pneumonitis.

• Brain ----- Chronic exposure Tremor, Psychological problems

Health Effects

2) Inorganic Mercury:

• Gastrointestinal tract:

Corrosive to mucosal membranes Hemorrhagic Necrosis and rapid fluid loss Shock Death

• Kidneys:

Effects the Proximal Tubule Acute Renal Failure can develop within 24 to 48 hours

Health Effects

3) Organic Mercury/ Methyl Mercury:

Due to high lipid solubility Methyl Mercury easily crosses the placental barrier and blood brain barrier.

Maternal exposure ----- ingestion of contaminated food (fish, grain).

Clinical Triad: Ataxia, Dysarthria, and constriction of visual fields

Clinical Triad: - Ataxia - Dysarthria - Constriction of visual fields

Laboratory Evaluation

• Blood is an appropriate specimen for analysis after acute mercury exposure.

• A 24-hour urine specimen is preferred in cases of chronic exposure.

Treatment and Management

• Chelation therapy has been used successfully in treating patients who have ingested inorganic mercury or inhaled elemental mercury.

• No antidote exist for patient with organic mercury; supportive care is recommended.

Cadmium Toxicity

Exposure pathway

• Smoking:– Cigarette = 1-2 ug Cd

• Industrial Uses:– Industries dealing with

pigment, metal plating, plastics, batteries

Health Effect

• Acute Toxicity:

– Inhalation of Cadmium Fumes

Flu Like Illness that Resolves within 24 Hours

• Chronic Toxicity:

• Kidneys

– Cd ½ Life in Tubular Cells = 10 – 30 years

– Proximal Tubule Dysfunction:

• Proteinuria

• Excretion of Glucose and Amino Acids

• Excretion of Minerals: Phosphate and Calcium

Health Effect

• Skeletal System:

Due to increase Urinary Calcium exertion the bones mobilize calcium stores

Osteoporosis & Osteopenia, "Itai – Itai"

Health Effect

Laboratory Evaluation

• Blood Cadmium

• Urine Cadmium

• Urine Beta- 2 Microglobulin

Arsenic Toxicity

Exposure pathway

• Commercial Sources:– Wood Preservatives Arsenic is

an excellent pesticide, herbicide, and fungicide

• Occupational Sources:– used throughout the semi-

conductor industry.– Arsine Gas is used in computer

chips

Exposure pathway

• After absorption arsenic is bound to proteins in the blood and is rapidly distributed to the Liver, Kidneys, Lungs, and Gastro-Intestinal Tract within 24 hours.

• Two to four weeks after exposure arsenic can be identified in hair, skin and nails

• Acute Toxicity:– 1) Gastrointestinal Tract:

• Most prominent symptoms occur within minutes of ingestion

• Sloughs the entire GI Tract– Difficulty swallowing, intense abdominal pain,

projectile vomiting, Rice- Water Stools, Severe Dehydration

– Develop Shock due to Fluid loss

Health Effect

Health Effect

• Chronic Exposure:

1) Skin:• Hyperkeratosis of Palms and Soles• Increased risk for non-melanoma skin cancer

2) Peripheral Nervous System:• Neuropathy of extremities with a sensory & motor

component

Hyperkeratosis of Palms and Soles ( Arsenic Hand )

Laboratory Evaluation

– Blood: Acute toxicity (24 hours)

– Urine: Indicator of recent toxicity (48 hours)

– Hair: Useful for Chronic Toxicity (Weeks)

Treatment and Management

• Acute Toxicity:

– 1) Supportive Care:• Fluid Replacement

• Gastric Lavage

– 2) Chelating agents

Thank you