| | | quote | Originally posted by FieroReinke:
I saw this and thought I would post this for those who are welding in their shops. Experienced welders should already know the risks, but many of us are beginner welders and may not realize the risks.
http://www.brewracingframes.com/id75.htm
Summary: don't use brake cleaner to clean the surface before you weld. The brake cleaner, argon gas, and heat combine to make Phosgene which is a very bad nuro toxin that can brain damage or even cause death with as little as a 4 PPM exposure.
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Not sure where you got the erroneous information that phosgene gas is a "nuro(sic) toxin" or that 4ppm can cause brain damage or death.
Proper ventilation and suitable safety precautions is all thats really required.
General Information
Description
Phosgene is a colorless, fuming liquid below 47ºF (8.2ºC) and a colorless, nonflammable gas above 47ºF. At low concentrations, its odor is similar to that of green corn or new mown hay; at high concentrations, its odor can be sharp and suffocating. Phosgene is slightly soluble in water and is hydrolyzed slowly by moisture to form hydrochloric acid. It is soluble in most liquid hydrocarbons. It is shipped as a liquefied, compressed gas. Large quantities of phosgene should be stored in a dry, cool, well-ventilated, and fireproof room. Phosgene is a combustion product of many household products that contain volatile organochlorine compounds. Therefore, it may contribute to the hazards of smoke inhalation in fire victims and firefighters.
Routes of Exposure
Inhalation
Inhalation is the major route of phosgene exposure. The odor threshold for phosgene is 5 times higher than the OSHA PEL. Thus, odor provides insufficient warning of hazardous concentrations. Phosgene's irritating quality can be mild and delayed, which may result in a lack of avoidance leading to exposure for prolonged periods. Phosgene is heavier than air and may cause asphyxiation in poorly ventilated, low-lying, or enclosed spaces.
Children exposed to the same levels of phosgene gas as adults may receive larger doses because they have greater lung surface area:body weight ratios and increased minute volumes:weight ratios. In addition, they may be exposed to higher levels than adults in the same location because of their short stature and the higher levels of phosgene gas found nearer to the ground.
Skin/Eye Contact
When phosgene gas contacts moist or wet skin, it may cause irritation and erythema. High airborne concentrations can also cause corneal inflammation and opacification. Direct contact with liquid phosgene under pressure can cause frostbite as well as severe irritation and corrosive effects.
Children are more vulnerable to toxicants affecting the skin because of their relatively larger surface area:body weight ratio.
Ingestion
Ingestion of phosgene is unlikely because it is a gas at room temperature.
Sources/Uses
Phosgene is produced commercially by chlorinating carbon monoxide. It is a combustion or decomposition by-product of most volatile chlorinated compounds; therefore, household substances such as certain solvents, paint removers, and dry-cleaning fluids can produce phosgene when exposed to heat or fire. Phosgene may also be produced during the welding of metal parts that have been cleaned with chlorinated hydrocarbons. Phosgene is used as an intermediate in the manufacture of many chemicals including isocyanates, polyurethane, polycarbonates, dyes, pesticides, and pharmaceuticals.
as a fumigant and a polymerization initiator.
Standards and Guidelines
OSHA PEL (permissible exposure limit) = 0.1 ppm (averaged over a 8-hour workshift)
NIOSH IDLH (immediately dangerous to life or health) = 2 ppm
AIHA ERPG-2 (emergency response planning guideline) (maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action) = 0.2 ppm
Physical Properties
Description: Colorless gas with musty odor at room temperature; a fuming liquid below 47ºF (8ºC).
Warning properties: Detectable odor following brief emergency releases; odor threshold 0.4 to 1.5 ppm; slightly irritating in high concentration. Odor provides inadequate warning of harmful concentrations.
Molecular weight: 98.9 daltons
Boiling point (760 mm Hg): 47ºF (8ºC)
Freezing point: -198ºF (-127ºC)
Specific gravity: 1.43 (liquid at 32ºF)
Vapor pressure: 1,215 mm Hg at 68ºF (20ºC)
Gas density: 3.48 (air = 1)
Water solubility: Slight
Flammability: Nonflammable gas
Incompatibilities
Phosgene reacts with moisture (water or alcohols). In water, it slowly decomposes to hydrochloric acid and carbon dioxide. When heated to decomposition, it will produce toxic and corrosive fumes. Phosgene reacts violently with various chemicals (e.g., alkalis, ammonia, amines, copper, aluminum); it attacks many metals in the presence of water and can also attack plastic and rubber.
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Health Effects
•Phosgene is an irritant to the skin, eyes, and respiratory tract; there may be minimal irritation immediately after exposure, but delayed damage may be severe.
•Common initial symptoms include mild irritation of the eyes and throat, with some coughing, choking, feeling of tightness in the chest, nausea and occasional vomiting, headache, and lacrimation.
•Phosgene poisoning may cause respiratory and cardiovascular failure, which results from low plasma volume, increased hemoglobin concentration, low blood pressure, and an accumulation of fluid in the lungs. Secondary systemic damage is the result of anoxia.
Acute Exposure
Phosgene directly reacts with amine, sulfhydryl, and alcohol groups in cells, thereby adversely affecting cell macromolecules and cell metabolism. Direct toxicity to the cells leads to an increase in capillary permeability, resulting in large shifts of body fluid, decreasing plasma volume. In addition, when phosgene hydrolyzes, it forms hydrochloric acid, which can also damage surface cells and cause cell death in the alveoli and bronchioles. Hydrochloric acid release into the mucosa triggers a systemic inflammatory response. Phosgene stimulates the synthesis of lipoxygenase-derived leukotrienes, which attract neutrophils and causes their massive accumulation in the lungs; this contributes to the development of pulmonary edema. Following phosgene exposure, a patient may be free of symptoms for 30 minutes to 48 hours before respiratory damage becomes evident; the more severe the exposure, the shorter the latency. If the initial concentration of phosgene was high, rapid onset of direct cytotoxicity and enzymatic poisoning may ensue. Because phosgene is not very water soluble and hydrolysis tends to be slow, victims inhaling low concentrations of the gas may experience no irritation or only mild irritation of the upper airway. Lack of irritation allows victims to inhale the gas more deeply into the lungs and for prolonged periods.
Children do not always respond to chemicals in the same way that adults do. Different protocols for managing their care may be needed.
Acute Exposure
Inhaling low concentrations of phosgene may cause no signs or symptoms initially, or symptoms may be due only to mild irritation of the airways; these symptoms (dryness and burning of the throat and cough) may cease when the patient is removed from exposure. However, after an asymptomatic interval of 30 minutes to 48 hours, in those developing severe pulmonary damage, progressive pulmonary edema develops rapidly with shallow rapid respiration, cyanosis, and a painful paroxysmal cough producing large amounts of frothy white or yellowish liquid. Inadequate, labored respiration, during which abnormal chest sounds are evident, may be accompanied by increased distress and apprehension. Insufficient oxygenation of arterial blood, and massive accumulation of fluid in the lungs may be accompanied by cardiovascular and hematological signs.
Exposure to phosgene has been reported to result in Reactive Airway Dysfunction Syndrome (RADS), a chemically- or irritant-induced type of asthma.
Children may be more vulnerable to corrosive agents than adults because of the relatively smaller diameter of their airways. Children may also be more vulnerable because of increased minute ventilation per kg and failure to evacuate an area promptly when exposed.
Respiratory
Inhaling low concentrations of phosgene may cause no signs or symptoms initially, or symptoms may be due only to mild irritation of the airways; these symptoms (dryness and burning of the throat and cough) may cease when the patient is removed from exposure. However, after an asymptomatic interval of 30 minutes to 48 hours, in those developing severe pulmonary damage, progressive pulmonary edema develops rapidly with shallow rapid respiration, cyanosis, and a painful paroxysmal cough producing large amounts of frothy white or yellowish liquid. Inadequate, labored respiration, during which abnormal chest sounds are evident, may be accompanied by increased distress and apprehension. Insufficient oxygenation of arterial blood, and massive accumulation of fluid in the lungs may be accompanied by cardiovascular and hematological signs.
Exposure to phosgene has been reported to result in Reactive Airway Dysfunction Syndrome (RADS), a chemically- or irritant-induced type of asthma.
Children may be more vulnerable to corrosive agents than adults because of the relatively smaller diameter of their airways. Children may also be more vulnerable because of increased minute ventilation per kg and failure to evacuate an area promptly when exposed.
Cardiovascular
Cardiovascular collapse may occur if the patient is severely hypovolemic and hypoxemic from accumulation of fluid in the lungs. Destruction of red blood cells in the pulmonary circulation can cause capillary plugging that leads to strain on the right side of the heart and death.
Dermal
If the skin is wet or moist, contact with phosgene vapor can cause irritation and redness of the skin. Contact with liquid phosgene under pressure can result in frostbite.
Because of their relatively larger surface area:body weight ratio, children are more vulnerable to toxicants affecting the skin.
Ocular
High vapor concentrations cause tearing and increased presence of blood in the eye. Contact with liquid phosgene may result in clouding of the cornea and delayed perforation.
Hematologic
In severe cases, phosgene may cause hemolysis that results in the plugging of pulmonary capillaries.
Most hematologic changes (e.g., hemolysis, methemoglobinemia, bone marrow suppression, and anemia) can be detected by standard blood tests.
Hepatic
In cases of high exposures, phosgene may be directly cytotoxic to the liver, causing necrosis and loss of function.
Renal
In cases of high exposures, phosgene may be directly cytotoxic to the kidneys, causing necrosis and loss of function.
Gastrointestinal
Nausea and vomiting may occur following exposure to phosgene.
Potential Sequelae
If the patient survives the initial 48 hours after exposure, recovery is likely. Sensitivity to irritants may persist, causing bronchospasm and chronic inflammation of the bronchioles. Pulmonary tissue destruction and scarring may lead to chronic dilation of the bronchi, lobular emphysema, regions of atelectasis, and increased susceptibility to infection.
Exposure to phosgene has been reported to result in Reactive Airway Dysfunction Syndrome (RADS), a chemically- or irritant-induced type of asthma.
Chronic Exposure
A group of workers who were exposed daily to high levels of phosgene showed an increase in mortality and morbidity from inflammation of the lungs, chronic inflammation of the bronchioles, destruction of alveoli, and impaired pulmonary function. Chronic exposures to low levels of phosgene may lead to chronic pneumonitis, which may resolve or lead to pulmonary edema.
Chronic exposure may be more serious for children because of their potential longer latency period.
Carcinogenicity
Phosgene has not been classified for carcinogenic effects.
Reproductive and Developmental Effects
No information was found pertaining to reproductive or
developmental hazards caused by phosgene exposure. Phosgene is not included in Reproductive and Developmental Toxicants, a 1991 report published by the U.S. General Accounting Office (GAO) that lists 30 chemicals of concern because of widely acknowledged reproductive and developmental consequences.
http://www.atsdr.cdc.gov/MHMI/mmg176.html[This message has been edited by randye (edited 02-22-2010).]
