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SKIN  EXPOSURE  LINKED  TO  RESPIRATORY  SENSITISATION   -

THE ISOCYANATE CONNECTION:

Photosol's latest research at AEA Technology in Harwell, is to look at potential unreacted GA on the surface of X-ray film as an unrecognised source of exposure.  This may tie in with isocyanate research:  "Work on isocyanates is some years ahead but the conundrum of how respiratory sensitisation could occur when measured air concentrations are so low is central also to isocyanate research.  Legislators have driven down permissable airborne concentrations to a few parts per billion. (In Britain the MEL for GA is proposed at 50ppb; isocyanates have a MEL of 12 ppb.)  But sensitization still occurs."  In a  paper called 

A Holistic Approach to Isocyanate Exposure Monitoring, Tom Klingner links skin exposure to respiratory sensitisation suggesting that by focusing on airborne induced asthmatic response, we have worsened immune sensitisation via dermal exposure and we may be eliminating a natural homeopathic exposure that protects.  (Source of paper unknown.) 

Several papers have been published which indicate respiratory sensitivity to isocyanates may be related to previous dermal exposure including:  *Kimber I.  The role of the skin in development of chemical respiratory hypersensitivity.  Toxicology Letters. 1996, 86, 89-92.  

*Bickis U,  Nakatsu K.  A single skin dontact with toluene diiocyanate (TDI) causes a one-year persistance of airway sensitisation, demonstrable in vivo and in vitro.  Am Hyg Conf and Exposition 1996,  No 310.X-ray chemicals and/or fumes  also contain;-acetic acid,  one of the main airborne contaminants at concentrations of about 0.1ppm in typical    X-ray film processing environments.[1]  In the simulated 'worst-case conditions' (see Scobbie et al, 1996 above), acetic acid was detected at 0.46ppm.  [The British OES is 10 ppm for an 8hr      time-weighted average (HSE, 1995).  The NZ TLV is 10ppm.  TLV - Threshold Limit Values - refers to airborne concentrations of substances under which it is believed that nearly all workers     may be repeatedly exposed day after day without adverse effect.  TLV is a ceiling limit which    should not be exceeded.]   Health effects:  irritating vapour to eyes, nose, throat, lungs;  inhalation of concentrated vapour may cause chronic inflammation of the lining membranes of the nose, throat and bronchi;  contact may cause severe damage to the eyes and skin.  Prolonged exposure           may cause erosion of the front teeth and darkening  (M A Gordon/ACC 1990);  experimental,            reproductive and mutagenic effects  (Sax/Lewis 1989)

-sulphur dioxide, the second main airborne contaminant from Scobbie et al at concentrations of about   0.1ppm.[2]  [TLV 2ppm.  0.1 ppm is equivalent to 1/20th of the OES of  2 ppm as an 8 hr     time-  weighted average (HSE, 1995).]  Detected in the simulated worse case conditions at around 0.5 ppm and in the exhaust duct at around 0.8 ppm.  Health Effects:  Particularly irritating to mucous membranes of URT; chronic effects include rhinitis, dry throat and cough.  Conjunctivitis, corneal burns, corneal opacity from direct contact.  Systemic effects from moderate exposure include bronchoconstriction  with increased pulmonary resistance, high pitched rales, though bronchoconstriction may be asymptomatic. Chronic exposure may result in nasopharyngitis, fatigue, altered sense of smell and chronic bronchitis symptoms.  Slight tolerance and general acclimatisation are common.  Sensitisation in a few individuals may develop following repeated exposures.  The effects on pulmonary function are increased in the presence of respirable particles.

"In guinea pigs, short-term exposure to the ubiquitous air pollutant sulfur dioxide, even at levels below national ambient air quality standards, augments subsequent allergic sensitization of the airways  (Reidel 1988).  Under the microscope, the bronchi (large airways) in sulphur dioxide exposed guinea pigs appear inflamed and thus may be more permeable, facilitating access of antigens to the immune system..."[3]

Scobbie et al: " Survey in a problem area:  Although these concentrations are well within the respective OESs, the investigating team found the conditions in this processing area considerably more uncomfortable ...  Concentrations of  [sulphur dioxide and acetic acid] in the headspace above the fixer were much higher than in the general room environment.  This indicates higher short-term exposures... might occur if operators were directly involved in handling the solutions" (p 429).  The concentration of sulphur dioxide and acetic acid in the exhaust duct and problem area "suggests the possibility of localised elevated concentrations in the absence of an exhaust duct" (p 430).

X-Ray chemicals which are involatile in solution (although may be present in fumes/aerosols) include:

- a glycol solvent, type of alcohol.  Diethylene glycol (2,2'-Oxydiethanol) - mostly used,poisonous by            inhalation, moderately toxic by ingestion, eye and skin irritant or  monoethylene glycol           (antifreeze).  Monopropylene glycol  which has much lower toxicity is increasingly used eg by Photosol.  Photosol fume surveys occasionally find some glycols.Scobbie et al  found  <0.05ppm  in the simulated problem location and <0.06ppm in the exhaust duct.  UK long term exposure limit (OES) is 23 ppm.  Glycols may attack  liver, kidneys, central nervous system. Metabolises to oxalic acid in the body.  From Terra Nova, 22 Jan, 98:  French concerns about ethylene glycols producing malformation of the embryo and foetus during pregnancy and increasing risk of congenital malformation in children whose mothers were exposed to glycol ethers in the workplace during pregnancy, have resulted in a ban on the use of glycol ethers in made-up medicine (eg for acne) and cosmetics.  The French consumer magazine has denounced the fact that the dangerous solvents are still on sale in window cleaners, detergents, oven cleaners, glues, pesticides and cosmetics.

-hydroquinone,  a benzene derivative;  the dust is a skin sensitiser.  An active allergen;  human poison by      ingestion, and suspected carcinogen.  "The ingestion of one gram by an adult may induce tinnitus, nausea, dizziness, a sensation of suffocation, an increased rate of respiration, vomiting, pallor, muscular twitchings, headache, dyspnea, cyanosis...." (Irving Sax).  Hydroquinone in aqueous    solution may take longer to manifest an allergic skin reaction but this is still possible if there is a predisposition to allergies. (Lila C.Albin, Ph.D., Dept. REM, Purdue University). Photosol have developed a hydroquinone-free Xray developer. 

-5-nitroindazole,  a benzene-derived irritant; irritating to eyes, respiratory system and skin  (James   Robinson Ltd,  MSDS, 1996),  and mutagen  (National Toxicology Group, 1996), developed by the US Military,  present in very small quantities, not much info available.

- potassium/sodium hydroxide,  caustic and corrosive.

-potassium/sodium metabisulphite,  potential sensitiser.

-phenidone,  dust irritating to eyes, skin, respiratory system - (Gordon/ACC).  A poison by ingestion -  Sax N, Lewis R  Dangerous Properties of Industrial Materials 7th Edition, NY,  Van Nostrand Reinhold, 1989. Long term effects unknown. 

-sulphuric acid

-alumimium sulphate

-ammonium/sodium thiosulphate,  heated can give off toxic fumes of sulphurous oxides  (interestingly, two Canadian radiographers recently skin tested positive to goldsodium thiosulphate).

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