A chemical burn ensues after contact with or ingestion of a toxic agent. Since chemicals are found in many products used at home and at the workplace, there is significant potential for injury.
Presentation
The common injury sites are the face, eyes, arms, hands, and legs. Many burns are small and require mild treatment in the outpatient setting. Note that the extent of the wounds may not be as apparent visually.
The presentation may be unpredictable and even deceiving. The clinical picture may feature any of the following signs at the site of contact: redness, irritation, burning, pain, numbness, blister formation, or darkened skin. Symptoms may include a cough, dyspnea, or emesis. If the eyes are affected, there is a risk of visual loss.
Patients with severe injuries may experience weakness, dizziness, loss of consciousness, dyspnea, and a cough. Additionally, life-threatening manifestations include hypotension, seizures, and arrhythmias.
Physical exam
The severity is determined by the depth and the percentage of the affected body surface according to charts available to clinicians. For example, in adults, the arm comprises 9% of the body surface.
The classification of burns
The depth of damage is as follows:
First-degree burns are superficial and involve the epidermis. Furthermore, second-degree injuries describe an extension into the dermal layer. This depth may be categorized as superficial or deep depending on the level of damage in the dermis. Finally, third-degree burns encompass the epidermis, dermis, and the underlying fat layer. Additionally, other structures are also affected such as hair follicles, sweat glands, and nerve endings.
All first-degree burns are considered minor. Also, second-degree injuries that involve less than 10% of the body are minor.
Moderate and severe burns are comprised of injuries sustained to the face, hands, feet, or genitals, as well as second-degree burns that affect greater than 10% of the body surface and all third-degree burns.
Entire Body System
- Weakness
This is a weak acid, and, in dilute form, it will not cause immediate burning or pain on contact. [emedicine.com]
- Inflammation
A first-degree burn is superficial and causes local inflammation of the skin. Sunburns often are categorized as first-degree burns. The inflammation is characterized by pain, redness, and a mild amount of swelling. [medicinenet.com]
While so-called lipid-laden macrophages are seen in cases of lipoid pneumonia, they can also form because of general inflammation and damage to the lungs. [scientificamerican.com]
If you can get into a dermatologists office, we would probably do what we sometimes call a quick fix – a steroid shot which would get rid of the inflammation in the fastest time possible. [realself.com]
Furthermore, there is high possibility of a poor prognosis, which includes inflammation, hypertrophic scar formation and pigmentation associated with its misuse. [ncbi.nlm.nih.gov]
- Burning Pain
After a 3-hour surgery, the patient complained of burning pain over the back at the recovery room. Physical examination revealed a 9 x 11 cm area of skin lesion partially thickened amid on the middle of the back suggestive of chemical burn. [ncbi.nlm.nih.gov]
Next day, he had burning pain with edema on his forehead, and his pain got worse. He presented to our hospital. A physical examination revealed yellowish-gray crust adherent to skin ulcers on his forehead. [ci.nii.ac.jp]
Half an hour into the procedure she experienced a stinging, burning pain on the scalp localized to the region where the dye chemicals were applied and she put her head under cold, running water to ease the pain. [medicaljournals.se]
However, significant burns require emergent care and stronger pain medications. [symptoma.com]
Respiratoric
- Cough
Symptoms include itching, bleaching or darkening of skin, burning sensations, trouble breathing, coughing blood and/or tissue necrosis. [en.wikipedia.org]
The 118 victims were mostly young men with 5%TBSA deep thickness burn of both lower extremities, including 31 patients who had additional light coughing. Of 58 patients who were finally hospitalized, 42 patients received surgical treatment. [ncbi.nlm.nih.gov]
[…] or shortness of breath Vomiting In severe cases, a person may develop any of the following symptoms: Low blood pressure Faintness, weakness, dizziness Shortness of breath or severe cough Headache Muscle twitching or seizures Cardiac arrest or irregular [ehsdb.com]
[…] or shortness of breath In severe cases, you may develop any of the following: Low blood pressure Faintness, weakness, dizziness Shortness of breath Severe cough Headache Muscle twitching or seizures Irregular heartbeat Cardiac arrest Chemical burns can [webmd.com]
- Pneumonia
What they did not find was evidence of lipoid pneumonia, which occurs when fats enter the lungs. [statnews.com]
Simon said, “You have pneumonia, and you’re going to the hospital.” julie bosman And he was in the hospital for a week. [nytimes.com]
- Aspiration
There is high concern about aspiration, increased tissue damage with retching, and a strong possibility of exacerbating a bad situation. [statpearls.com]
Gastrointestinal
- Vomiting
[…] your healthcare provider right away if any of these occur: Swelling or pain gets worse Redness gets worse Fluid or pus drains from the burn area Fever of 100.4°F (38°C) or higher, or as directed by your healthcare provider Wound doesn't heal Nausea or vomiting [fairview.org]
Symptoms of a chemical burn include abdominal pain, breathing difficulty, bright red or bluish skin and lips, headache, weakness, dizziness, seizures, unconsciousness, nausea, vomiting, hives, itching, rash, blisters, swelling and pain where the skin [livescience.com]
[…] include: Abdominal pain Breathing difficulty Bright red or bluish skin and lips Convulsions (seizures) Dizziness Eye pain, burning or watering Headache Hives, itching, swelling, or weakness resulting from an allergic reaction Irritability Nausea and/or vomiting [mountsinai.org]
[…] symptoms include: Redness, irritation, or burning at the site of contact Pain or numbness at the site of contact More serious symptoms that warrant seeking immediate medical attention include: Formation of blisters or black dead skin at the contact site Vomiting [walkermorgan.com]
Some lesser known signs of a chemical burn are: Blurred vision Vomiting Shortness of breath In more severe cases, burn injury victims have been known to exhibit symptoms such as: Dizziness Headache Low blood pressure When all of the immediate dangers [fortheinjured.com]
- Nausea
[…] advice Call your healthcare provider right away if any of these occur: Swelling or pain gets worse Redness gets worse Fluid or pus drains from the burn area Fever of 100.4°F (38°C) or higher, or as directed by your healthcare provider Wound doesn't heal Nausea [fairview.org]
Syncope can either occur suddenly without any warning symptoms or can be preceded by sweating, nausea, blurred vision, pale skin and lightheadedness. +What Causes Syncope? +How Is Syncope Diagnosed and Treated? + + + + + + + + [biotronik.com]
Symptoms of a chemical burn include abdominal pain, breathing difficulty, bright red or bluish skin and lips, headache, weakness, dizziness, seizures, unconsciousness, nausea, vomiting, hives, itching, rash, blisters, swelling and pain where the skin [livescience.com]
[…] symptoms may include: Abdominal pain Breathing difficulty Bright red or bluish skin and lips Convulsions (seizures) Dizziness Eye pain, burning or watering Headache Hives, itching, swelling, or weakness resulting from an allergic reaction Irritability Nausea [mountsinai.org]
- Diarrhea
The most common side effects caused by garlic range from gastrointestinal upset, nausea, to heartburn to diarrhea. It has also been reported to show platelet dysfunctions leading to postoperative bleeding and spontaneous epidural hematoma. [srmjrds.in]
Cardiovascular
- Thrombosis
This intra-arterial infusion avoids the disadvantages of local infiltration therapy; however, it is an invasive procedure that may result in arterial spasm or even thrombosis. [reliasmedia.com]
Eyes
- Blepharospasm
Symptoms The most common symptoms are severe pain, epiphora, blepharospasm, and reduced visual acuity. Irrigation Early irrigation is critical in limiting the duration of chemical exposure. [eyewiki.aao.org]
Ocular Burns Chemical burns to the eyes are common and considered true ocular emergencies requiring immediate treatment.10 Early signs and symptoms of eye burns include tearing, rubbing, redness, pain, and blepharospasm. [reliasmedia.com]
- Lacrimation
Death resulting from lacrimator agents. J Forensic Sci 1978;23:527-530. 68. Thornburn KM. Injuries after use of the lacrimator agent chloroacetophenone in a confined space. Arch Environ Health 1982;37:182-186. 69. Blain PG. [reliasmedia.com]
Musculoskeletal
- Contusion
Airbags can produce abrasions, lacerations and contusions through the physical force of the rapid expansion. They can also produce alkaline chemical burns. [emedicine.com]
- Fracture
(disease), 039880, fracture, 頭蓋骨, ズガイコツ, skull, 023457, 洗浄, センジョウ, cleaning(washing), 004352, cleaning, ワセリン, ワセリン, vaseline, 022125, 治療法, チリョウホウ, therapy, 040918, 保存療法, ホゾンリョウホウ, conservative treatment, 057663, 合併症, ガッペイショウ, complication, 054094 [togodb.biosciencedbc.jp]
Product involved Nature of the product, concentration and length of exposure: sometimes specific first aid measures (rinsing time, antidote, …) Other Age and health status of the injured person, possible other lesions associated with the accident (fractures [santemontreal.qc.ca]
[…] the field of endodontics as lining of cavities, indirect and direct pulp capping, dressing after pulpotomy, dressing of the root canal between appointments, prevention of root resorption, repair of iatrogenic perforations, treatment of horizontal root fractures [srmjrds.in]
Skin
- Blister
"She has blisters from her finger to her elbow and is in so much pain." [thesun.co.uk]
[…] roundup.jpg 2 606 × 2 525; 1,93 MB Blister-arm.jpg 350 × 235; 7 KB Blister-back.jpg 379 × 224; 9 KB Charakteristische Brandwunde von Wasserstoffperoxid H2O2.jpg 864 × 864; 123 KB Chemical burn injury..jpg 300 × 226; 56 KB Chemical burns follwong Israeli [commons.wikimedia.org]
If the burn has blistered or has removed the top layer of skin, you have a second-degree chemical burn. [healthfully.com]
Don't break blisters open. Broken blisters could get infected. If a blister breaks open by itself, blot up the liquid, and leave the skin that covered the blister. This helps protect the new skin. Try not to scratch the burn. [myhealth.alberta.ca]
- Ulcer
This study reports a unique case of a Marjolin ulcer in a patient who presented with periocular sebaceous cell carcinoma 16 years after a lye chemical burn. [ncbi.nlm.nih.gov]
A physical examination revealed yellowish-gray crust adherent to skin ulcers on his forehead. The crust was removed with surgical debridement, followed by topical ointment of alprostadil alfadex. His ulcer healed in 1 week. [ci.nii.ac.jp]
Alendronate-related oral mucosa ulcerations. J Oral Pathol Med 2000;29:514-8. 17. Krasagakis K, Krüger-Krasagakis S, Ioannidou D, Tosca A. Chronic erosive and ulcerative oral lesions caused by incorrect administration of alendronate. [srmjrds.in]
- Formication
[…] acid burn 11719311 - Formic acid burn 11719308 - Chemical burns 11719306 - Chemical burns 11684175 - Detergent burn to child's eye 11672832 - Mustard gas burns,War War I 11719310 - Formic acid burn 11618228 - Mustard gas burns,First World War 13418091 [sciencephoto.fr]
We report on a 26-year-old woman who during early infancy (6 months) suffered from a chemical burn of the skin and upper airways due to spill of formic acid powder. [ncbi.nlm.nih.gov]
The pharmacist should be closely involved when burns are caused by medications like podophyllotoxin, formic acid or topical salicylic acid. [statpearls.com]
Formic acid is used in the tanning industry as well as in glue making. It creates a deep eschar that does not protect the body from systemic effects. Some total-body effects include lung problems, kidney failure and breakdown of hemoglobin. [autoaccident.com]
- Skin Lesion
Physical examination revealed a 9 x 11 cm area of skin lesion partially thickened amid on the middle of the back suggestive of chemical burn. After conservative treatment, she was discharged uneventfully 4 days later. [ncbi.nlm.nih.gov]
The lesions are typically erythematous with blister formation. The skin damage continues as long as the agent remains in contact with the skin and, for this reason, the blister should be debrided and drained and copiously irrigated with water. [reliasmedia.com]
The specific components of garlic responsible for skin lesions remain unknown. Garlic contact dermatitis, type IV allergic reactions limited to epidermis, has been attributed principally to diallyl disulfide, allyl propyl disulfide, and allicin. [srmjrds.in]
- Eczema
An invisible spot on the thin-layer chromatography plate gave a test eczema and was further investigated with gas chromatography-mass spectrometry. DPGDA was detected in the spot. [ncbi.nlm.nih.gov]
In some cases, contact urticaria can be demonstrated only on damaged or previously eczematous skin, and it can be part of the mechanism responsible for maintenance of chronic eczemas الصفحة 416 - Loveless SE, Ladies GS, Gerberick GF, et al. (1996) Further [books.google.com]
Urogenital
- Kidney Failure
Some total-body effects include lung problems, kidney failure and breakdown of hemoglobin. It can cause damage to the pancreas and abdominal pain. Hydrochloric acid is considered one of the most common acid injuries. [autoaccident.com]
In fact, chromates cause significant skin injuries and systemic toxicity such as kidney failure. Other Phosphorous is present in fireworks, munitions, and fertilizer. [symptoma.com]
Ingestion of even small amounts may result in death with severe metabolic acidosis, kidney failure, and hepatotoxicity. Oral ingestion will cause significant injury of the esophagus and stomach. [reliasmedia.com]
Neurologic
- Paresthesia
Concentrations of 10% may cause paresthesias and blanching of the skin. Concentrations of 35% or more will cause immediate blistering. [emedicine.com]
Workup
Clinical evaluation includes the history of exposure, identification of the offending agent, a physical exam, and investigations.
Laboratory tests
Note that the studies are selected based on the severity and causes of the chemical burn.
In severe injuries, the clinician should obtain electrolytes, complete blood count (CBC), creatinine, blood urea nitrogen (BUN), glucose, urinalysis creatine phosphokinase, and a coagulation profile.
If caustics are consumed, then hemoglobin and hematocrit measurements are warranted. Additionally, if there is respiratory involvement, this necessitates arterial blood gas (ABG) or other measures.
Calcium, magnesium, and potassium levels are obtained in hydrofluoric acid burns while creatinine and BUN are warranted in chromic acid injuries. Additionally, oxalic acid burns require calcium measurement.
Furthermore, electrolytes, CBC, creatinine levels, liver function tests (LFTs), and urinalysis are performed in patients with phenol injuries. Finally, electrolytes and ABG tests are indicated in monofluoroacetic acid burns.
Imaging procedures
Esophagoscopy and gastroscopy are indicated in cases suggestive of oral intake. For example, these studies are performed in patients with symptomatic ingestions and those who are asymptomatic but have previously ingested harmful substances [1] [2].
In patients with evidence of esophageal burns, the injury is described according to the layers it involves: superficial, transmucosal, or transmural.
Note that only 2% to 15% of patients with esophageal damages have oral burns.
Treatment
The treatment should be prompt. First aid should be applied immediately or as soon as possible. In fact, the chemical should be rinsed under running water for a duration of 10 to 20 minutes [7]. Likewise, if there is eye exposure, it should be rinsed for a minimum of 20 minutes prior to seeking emergency therapy. Also, all contaminated clothing or material on the body should be removed quickly.
Additionally, the burned area should be loosely wrapped in a sterile and dry dressing or cloth.
With regards to pain, superficial injuries can be treated with over-the-counter analgesics. However, significant burns require emergent care and stronger pain medications.
The patient must go to the nearest emergency room if the following signs are exhibited [8]:
- Shallow breathing
- Signs of shock
- Measurement of the burn is greater than 3 inches
- Injury involves the eyes, hands, feet, groin, buttocks, or major joint
- Over- the-counter analgesics do not achieve pain control
Management
Wound care therapy may include debridement, use of antibiotics and anti-itching medications, skin grafting, intravenous fluids, and specialized dressings.
Note that there are contraindications such as gastric emptying. For example, measures such as charcoal use or dilution with milk or water should be avoided. Anything that may compromise the airway or the endoscopic procedure is not permitted.
The clinician should be cautious of adding water to products that contain sulfuric acid or sodium hydroxide since the resultant reactions will produce heat. Hence, this heat formation can be limited if diluting with 250-500ml of fluid [9].
Prognosis
The outcomes of dermal burns are related to the degree of involvement. For example, first-degree and mild second-degree burns will typically recover in days to weeks. These do not usually produce scars. However, deep second-degree and mild third-degree require weeks to heal and are associated with scar formation. Also, skin grafting is commonly indicated with these injuries.
With regards to prognosis, there is a high risk of mortality with burns that affect greater than 90% of the body. In fact, in more advanced ages, greater than 60% may result in death.
As for specific manifestations, it depends on the location of the injuries. Caustic burns will produce scarring especially in certain areas of the body. Also, eye injuries may lead to blindness while esophageal and gastric burns may result in the formation of a stricture. Note that patients with full thickness esophageal burns are predisposed to stricture formation.
Etiology
There is a broad spectrum of industrial and commercial products that are composed of toxic levels of acids, bases, and other substances that cause burn injuries [1] [2].
Acids
There are multiple forms of an acid such as sulfuric acid, hydrofluoric acid, hydrochloric acid, phosphoric acid, acetic acid, formic acid, chloroacetic acid, phenols, and cresols.
Frequently found in drain cleaners, battery fluid, and fertilizer production is sulfuric acid. Some products contain 8% acid while others are made up of nearly 100% acid. Additionally, hydrofluoric acid is often present in tire cleaners, rust removers, tanning, petroleum refining and other products.
Another type, hydrochloric acid, is used in metal cleaners, dye manufacturing, swimming pool cleaners, and laboratory chemicals. The levels are anywhere from 5% to 44%. Furthermore, phosphoric acid is added in disinfectants, metal cleaners, and fertilizer products while acetic acid constitutes disinfectants and dyes. Also, formic acid is used in tanning and cellulose manufacturing.
Mono, di, and trichloroacetic acid are key ingredients in the manufacturing chemicals. Additionally, mono chloroacetic acid leads to systemic toxicity since it disrupts cellular respiration.
Other acids such as phenol are used in plastics, drugs, and disinfectants while cresol is used in wood preservatives and degreasing products.
Bases
Some of the most common bases are sodium hydroxide, calcium oxide, sodium and calcium hypochlorite, ammonia, phosphates, sodium carbonate, and lithium hydride. These are found in a variety of products. For example, sodium hydroxide is an ingredient in drain and denture cleaners while ammonia, sodium carbonate and phosphates are constituents in detergents.
Calcium oxide is the corrosive component in cement that causes burns if diluted with water. Meanwhile, bleach contains sodium and calcium hypochlorite. Along with sodium hydroxide, hypochlorite is also found in pool chlorinating mixes, which are caustic.
The space industry utilizes lithium hydride to absorb carbon dioxide. The reactions that occur with water produce hydrogen and lithium hydroxide which cause thermal and alkaline injuries.
Oxidants
Oxidants include bleach, peroxides, and chromates. Peroxides are key elements in hair dyes while chromates are components of industrial chemicals in tanning, painting, and printing. In fact, chromates cause significant skin injuries and systemic toxicity such as kidney failure.
Other
Phosphorous is present in fireworks, munitions, and fertilizer. Moreover, when these products explode, phosphorous residue remains on the skin and smolder [3]. Other potentially hazardous materials are hair dyes [4] as they may burn the scalp.
Chemical warfare products such as sulfur and nitrogen mustards are blistering agents.
Epidemiology
The emergency department frequently treats chemical injuries, and almost 5% of patients are admitted [5]. While the number of burns previously declined, it has been constantly steady since 2000.
Corrosive substances are used worldwide in aggressive situations. Furthermore, the likely victims of chemical assaults are women [6].
Pathophysiology
The pathogenic mechanisms differ in accordance to the type of offending substance.
This chemical causes coagulation necrosis through the denaturation of proteins. Furthermore, this injury develops a coagulum that restricts the penetration of the agent.
One exception is hydrofluoric acid, which produces a liquefaction necrosis.
Bases
These agents lead to liquefaction necrosis, which is a more significant injury. In addition to protein denaturation, fat saponification occurs as well. Moreover, penetration of tissue is permitted.
Factors related to severity
The pH, concentration, and volume of the chemical, as well as the duration of exposure, play a role in the degree of severity of the burn. Additionally, the site and method of contact, the type of chemical, and length of time to washing also influence the damage. For example, the consumption of solid form of alkaline products leads to increased length of contact time in the gastrointestinal tract. This is correlated with serious destruction. Similarly, concentrated products that are diluted or neutralized will develop heat and yield thermal and caustic damage.
Prevention
Preventive measures include wearing protective clothing on the body and eyes when handling chemicals. Additionally, everyone should follow safety precautions and directions. Finally, all chemical agents should be secured out of the reach of children.
Summary
A burn is a damage or an injury to the human tissue that occurs due to electricity, chemicals, heat, friction or various other factors. Chemical burns can result from various irritants such as acids, bases, and oxidants, all of which can be found in home products as well as products used in workplaces such as manufacturing plants. Since cleaners, disinfectants, fertilizers, laboratory products, and bleach all contain toxic substances, there is potential for accidental injuries.
The overall clinical picture of the burn depends on the chemical to which the exposure occurred. Furthermore, the factors that determine the extent of the tissue damage are the pH, concentration, and volume of the agent as well as the duration and method of contact. While some burns are minor, others may be so severe that systemic toxicity ensues.
The clinician should perform a thorough physical exam to identify the amount of body surface that is harmed as well as the depth of the tissue destruction. Also, the medical team should ascertain what the offending agent is if possible as this can guide the appropriate workup and treatment. If the chemical was ingested, then an esophagoscopy and a gastroscopy are warranted.
Regarding the first aid response, immediate removal of the contaminated clothing and washing of the affected sites are essential. Critically ill patients will need immediate medical attention and stabilization. Also, wound care, pain management, and other treatments may be indicated.
Regarding prevention, precautionary measures include following proper guidelines and wearing protective clothing when handling chemicals.
Patient Information
When a chemical comes in contact with the skin or eyes, this may cause a burn. These types of injuries may occur through accidental exposures with toxic products at home or in the workplace. Examples of the latter include chemical plants, pool maintenance, mining, fertilizer manufacturing, and the aerospace industry since all use heavy chemical and toxins. Therefore, employees in these professions are at risk for accidents and injuries.
The following toxic agents are used in various products:
- Bleach
- Ammonia
- Silver nitrate
- Hydrochloric acid
- Sulfuric acid
- Phosphoric acid
- Acetic acid
- Calcium hydroxide
- Sulfur mustard
- Vesicants
Skin burns exhibit the following:
- Rash
- Blistering
- Redness
- Pain
- Ulceration
In seriousness cases, the symptoms are:
- Breathing problems
- Abdominal pain
- Nausea
- Vomiting
- Seizures
- Headache
- Weakness
- Abnormal heart rhythm
- Death (in worst cases)
How are burns diagnosed?
The medical team will evaluate the extent and depth of the burns. In severe cases, the team will need to stabilize the patient. Also, they will obtain blood tests. If the chemical was ingested, then an esophagoscopy and gastroscopy are performed.
The symptoms depend on the chemical, the amount, the concentration, how long the skin was exposed to it, and whether the exposure was through skin contact or ingestion.
The burn is classified as a first, second, or third-degree depending on which layers of the skin are involved. Also important is the percentage of the body surface affected by the burn.
What is the treatment?
The treatment consists of pain management which can be achieved with over-the-counter analgesics such as acetaminophen. Also, antibiotics may be necessary. In severe cases, the patient may need skin grafting and other appropriate care and management.
How can burns be prevented?
All products and chemicals should be placed out of the reach of children. Additionally, everyone should follow the instructions when using these products. Finally, protective clothing and eye gear should be worn when handling chemical substances.
References
- Ramasamy K, Gumaste VV. Corrosive ingestion in adults. J Clin Gastroenterol. 2003; 37(2):119-24.
- Gorman RL, Khin-Maung-Gyi MT, Klein-Schwartz W, et al. Initial symptoms as predictors of esophageal injury in alkaline corrosive ingestions. Am J Emerg Med 1992; 10(3):189-94.
- Barillo DJ, Cancio LC, Goodwin CW. Treatment of white phosphorus and other chemical burn injuries at one burn center over a 51-year period. Burns. 2004; 30(5):448-52.
- Maguina P, Shah-Khan M, An G, et al. Chemical scalp burns after hair highlights. J Burn Care Res. 2007; 28(2):361-3.
- Taira BR, Singer AJ, Thode HC, et al. Burns in the Emergency Department: A National Perspective. J Emerg Med. 2010; 39(1):1-5.
- Mannan A, Ghani S, Clarke A, et al. Cases of chemical assault worldwide: a literature review. Burns. 2007; 33(2):149-54.
- Leonard LG, Scheulen JJ, Munster AM. Chemical burns: effect of prompt first aid. J Trauma. 1982; 22(5):420-3.
- Bertolini JC. Hydrofluoric acid: a review of toxicity. J Emerg Med. 1992; 10(2): 163-8.
- Friedman EM, Lovejoy FH. The emergency management of caustic ingestions. Emerg Med Clin North Am. 1984; 2(1):77-86.