Environmental Diseases By: K.Mozaffari , MD, AP, CP

INJURY BY PHYSICAL AGENTS Mechanical Thermal

MECHANICAL TRAUMA Abrasion Contusion Laceration Incised wound Puncture wound (Gunshot wounds)

Abrasion Superficial epidermal tears Bleeding under skin

Contusion (Bruise) Blunt object RBC extravasation Intact skin discoloration

Laceration Tear or streching of tissue Jagged & irregular edges Intact bridging Vessels

INCISED WOUND Made by a sharp instrument Bridging vessels are severed

Puncture Wounds Made by a long narrow instrument Penetrating: pierces tissues Perforating: traverses tissue to form an exit wound (Gunshot wounds)

Long distance & Close range

THERMAL INJURY Thermal burns Hyperthermia Hypothermia

Thermal burns 5000 deaths/yr in the U.S Many victims are children Factors: Depth Percentage Inhalational injury Effective therapy

Thermal burns A-Full-thickness: III & IV degree Epidermis & dermal appendages lost White, charred, dry or anesthetic B-Partial-thickness: I & II degree Appendages are spared Pink, mottled & painful Blisters form

If > 50 % of body surface: potentially fatal If > 20 %: hypovolemic shock & edema Inhalation of heat & gases 1-Water-soluble: forms acids or alkalis with upper airway obstruction (chlorine, sulfur oxides, ammonia) 2-Lipid-soluble: deeper airways with pneumonitis (nitrous oxide, plastics)

Burn sepsis →organ failure (leading cause of death) P.aeruginosa - S.aureus – Candida Cellular & humoral defenses fail Endotoxin from local site Renal failure, ARDS & septic shock Hypermetabolic state

Hyperthermia Heat exhaustion : most common, sudden onset Heat Cramps: → Exercise leads to cramps Electrolyte loss & nl core body temperature Heat exhaustion : most common, sudden onset water depletion→ collapse (spontaneously resolves) Heat stroke: temperature & humidity Sweating ceases → core body temperature: Vasodilation ,muscle necrosis, arrhythmias & DIC

Hypothermia ambient & body temperature At 90°F : loss of consciousness, bradycardia & AF Direct effects: crystals form Indirect effects: Slow onset ( Trench foot): edema & later atrophy with fibrosis Sudden onset ( Gangrene) :ischemia & later exudation

ELECTRICAL INJURY Burns (amperage & path within body) VF, cardiorespiratory arrest Tetanic muscle spasm of chest wall High voltage: Extensive burns, medullary paralysis

Electromagnetic fields ( EMFs ) The formerly believed relationship between increased risk of cancer & EMF failed to be confirmed But when intense they can cause burns Also interfere with pacemakers

Injury by ionizing radiation Waves: X , δ Neutrons & particles: proton, α , β DNA is the most important target types: 1-direct injury 2-indirect injury ( free radicals) Lipids of cell membrane & enzymatic proteins are also targeted

Roentgen: unit of X or δ that ionizes a specific volume of air (exposure measured) Rad =1cGy (centigray): 100erg energy/g tissue absorbed LET: (energy loss) electron volt/µm α > β > δ , X

α:restricted to a superficial area but with heavy damage δ:less damage over a deeper course Body cell types: 1)vulnerable,high turnover: GI,BM, lymphoid 2)slower turnover: liver ,endothelium 3)nondividing:myocardium,brain Tissues have many cell types with complex effects ( vessels in the CNS)

Radiotherapy Nl cells have faster repair than tumoral cells Oxygen effect (free radicals): center of tumors are less vascular → less effective therapy High dose given to a small field is better tolerated than small dose in larger fields Alters gene expression : MYC,FOS,TNF induction TP53 activation : apoptosis

Morhpology Molecular level: DNA breaks lead to apoptosis by TP53 Deletion, translocation, fragmentation, polyploidy, aneuploidy

Morhpology Nuclear level: Swelling, condensation, clumping, apoptosis Giant cells, pleomorphism At high doses, pyknosis & lysis are quick markers of cell death

Morhpology Cytoplasmic changes: Swelling mitochondrial distortion ER degeneration cell membrane breaks

Morhpology Early vascular changes: dilation→ endothelial swelling, vacuolation, wall necrosis, thrombosis rupture→ endothelial proliferation & medial thickening→ luminal obliteration Later, interstitial fibrosis leads to scarring & contractions

Acute vascular injury Fibrinoid necrosis edema

Chronic vascular injury Subintimal fibrosis Lumen is occluded

Radiation fibrosis of breast stroma Pleomorphic residual tumoral cells with multinucleation

Mediastinal fibrosis Pericardium is thick after radiation in a case of lung ca

Chronic radiation dermatitis Epidermal atrophy Dermal fibrosis Subcutaneous vessels (telangiectasia)

Radiation effects on organ systems Lymphopenia & shrinkage of lymphoid systems (thymus)

Radiation effects on organ systems Granulocytes first rise, then fall to zero in the 2nd wk Platelets are similarly affected but with some delay Red cell precursors → anemia in 2nd -3rd wk (RBCs are resistant )

Malignant transformation: Sublethal high doses: -Hiroshima & Chernobyl victims -radiologists Prolonged low-dose exposure: -radon daughters (α) : lung ca

Total-Body Irradiation Even small doses can be devastating 100-300 rad: acute radiation syndrome Lethal range begins at 200 rads Death is certain at 700 rads without Rx

syndromes Dose (rad) Manifestations Hematopoietic 200-500 N&V cytopenias GI tract 500-1000 Severe sx diarrhea Hemorrhage Cerebral >5000 Listlessness drowsiness Convulsions Coma & death

MCQ 1 Which type of wound is produced by rubbing in which only the epidermal layer is removed? 1-laceration 2-abrasion 3-contusion 4-incision

MCQ 2 The primary target of ionizing radiation is? 1-RNA 2-DNA 3-Lipids 4-Proteins

MCQ 3 What is this lesion?

Abrasion

MCQ 4 Which cells are resistant to radiation? 1-gastrointestinal tract cells 2-lymphocytes 3-red blood cells 4-granulocytes

MCQ 5 A Full-thickness burn is not… 1-Pink, mottled, painful 2-anesthetic 3-III & IV degree 4-White, charred or dry

MCQ 6 What are the lesions?

Contusion (Bruise)

MCQ 7

laceration

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