Sulfur mustard human exposure

Recently, sulfur mustard has been shown to alkylate a cysteine residue in human serum albumin (10). The site of alkylation was identified in a tryptic digest of albumin from blood exposed to [14C]sulfur mustard. A sensitive method for its analysis was developed based on Pronase digestion of alkylated albumin to the tripeptide S-[2-[(hydroxyethyl)thio]ethyl-Cys-Pro-Phe, and detection using micro-LC-MS-MS. In vitro exposure of human blood to > 10 nM sulfur mustard could be detected employing this method. The analytical procedure was successfully applied to albumin samples from Iranian casualties of the Iraq-Iran war. 

Because of the correlation between mutagenicity and carcinogenicity, one would expect sulfur mustard to be carcinogenic on the basis of mutagenicity data alone. This expectation is borne out by carcinogenicity tests in experimental animals and by data from human exposures. The International Agency for Research on Cancer classifies sulfur mustard as one of relatively few chemical agents on which the data are adequate to show an association with the induction of cancer in humans.7... 

Sulfur mustards (designated H [mustard], HD [distilled mustard], and HT [HD and T mixture]) do not present acute lethal hazards. Their principal effect is severe blistering of the skin and mucous membranes. Epidemiological evidence indicates a causal relationship between exposure to mustard agent at high concentrations and the development of chronic nonreversible respiratory disorders, such as chronic bronchitis and asthma, and ocular diseases, such as delayed recurrent keratitis and prolonged, intractable conjunctivitis (IOM, 1993). Sulfur mustard has been classified as a known human carcinogen based on evidence of in-... 

D. Noort, A.G. Hulst, L.P.A. De Jong and H.P. Benschop, Alkylation of human serum albumin by sulfur mustard in vitro and in vivo mass spectrometric analysis of a cysteine adduct as a sensitive biomarker of exposure, Chem. Res. Toxicol, 12, 715-721 (1999). 

This paper will review the known metabolic pathways of CW agents, excretion profiles where these have been measured, and methods for the analysis of metabolites in urine or blood. Examples are provided of detection in cases of human exposure. The review focuses mainly on sulfur mustard and nerve agents that represent the greatest global CW threat, and for which most analytical methods have been developed. 

Analytical methods have been reported for unchanged agent and six of the urinary excretion products described above. These are TDG, TDGO, the bis A-acetylcysteine conjugate (1), two 3-lyase metabolites (2) and (3), and the guanine adduct (6). These methods have been applied to animal and/or human exposures to sulfur mustard. 

E.M.Jakubowski Read, F.R. SideU, R.A. Evans, M.A. Carter, J.R. Keeler, J.D. McMonagle, A. Swift, J.R. Smith and T.W. Dolzine, Quantification of thiodiglycol in human urine after an accidental sulfur mustard exposure, Toxicol. Methods, 10, 143-150 (2000). 

The ELISA for detection of the DNA adduct was successfully applied to blood samples from two casualties of the Iraq-Iran conflict. These samples were collected 22 and 26 days following the alleged exposure to sulfur mustard (13). Concentrations found in lymphocytes and granulocytes were equivalent to similar levels found in human blood after treatment in vitro with 0.015-0.43 xM sulfur mustard. 

Distribution studies of 35S-sulfur mustard in rats after cutaneous exposure to sulfur mustard, and human blood treated in vitro, showed that a small percentage of radioactivity remained associated with the hemoglobin and persisted for the lifetime of the... 

Figure 4. Persistence of sulfur mustard adduct to N-terminal valine residue of hemoglobin in blood of a marmoset after sulfur mustard administration (4.1 mg/kg, i.v.) at t = 0. At the time points indicated blood samples were collected, globin was isolated and analyzed by using the modified Edman degradation for determination of the N-terminal valine adduct. Globin from human blood exposed to ris-sulfur mustard (10 iM) was used as an internal standard. (Reprinted from Toxicology and Applied Pharmacology, Vol. 184, D. Noort, H.P. Benschop and R.M. Black, Biomonitoring of Exposure to Chemical Warfare Agents A Review, pages 116-126 (2002), with permission from Elsevier Science.)...

The analytical procedure for S-[2-[(hydroxyethyl) thio]ethyl-Cys-Pro-Phe was successfully applied to blood samples from nine Iranian casualties of the Iraq-Iran war, all exhibiting skin injuries compatible with exposure to sulfur mustard. The blood samples were collected 8-9 days after the alleged exposure and stored at — 70 °C. The albumin adduct was detected in all cases, at levels estimated as corresponding to those after in vitro exposure of human blood to mustard concentrations ranging from 0.4-1.8 xM. 

The use of sulfur mustard as a vesicant CW agent implies that proteins of the skin are a primary target. It was found that upon exposure of human callus to [14C]sulfur mustard, a significant part of the radioactivity was covalently bound to keratin (30). Most of the radioactivity (80%) bound to keratin could be removed by treatment with alkali, indicating the presence of adducts to glutamic and/or aspartic acid residues. 

The skin and eyes are especially sensitive to the toxic effects of sulfur mustard. When applied to human skin, about 80% of the dose evaporates and 20% is absorbed (Vogt et al., 1984). About 12% of the amount absorbed remains at the site and the remainder is distributed systemically (Renshaw, 1946). Doses up to 50 pg/ cm cause erythema, edema, and sometimes small vesicles. Doses of 50-150 pg/cm cause bullous-type vesicles, and larger doses cause necrosis and ulceration with peripheral vesication. Droplets of liquid sulfur mustard containing as little as 0.0025 mg may cause erythema (Ward et al., 1966). Eczematous sensitization reactions were reported in several early studies and may occur at concentrations below those causing direct primary irritation (Rosenblatt et al., 1975). In humans, the LCtso (estimated concentration x exposure period lethal to 50% of exposed individuals) for skin exposures is 10,000 mg-min/m (DA, 1974) (for masked personnel however, the amount of body surface area exposed was not reported). The ICt 50 (estimated concentration x exposure period incapacitating to 50% of exposed individuals) for skin exposures is 2000 mg-min/m at 70-80°F in a humid enviromnent and 1000 mg-min/m at 90°F in a dry enviromnent (DA, 1974, 1992). The ICtso for contact with the eyes is 200 mg-min/m (DA, 1974, 1992). The LDl for skin exposure is 64 mg/kg and the LD50 is estimated to be about 100 mg/kg (DA, 1974,1992). 

The LCtso for inhalation exposures in humans has been estimated to be 1500 mg-min/m (DA, 1992). In animals, median lethal Ct values for sulfur mustard range from 600 to 1900 mg-min/m for 10-min exposures (see Rosenblatt et al., 1975 for review). An LClo (lowest lethal concentration) of 189 mg/m /10 min has been reported for mice (Lewis and Sweet, 1984), and a 5-min LClo of 77 ppm has been reported for dogs (fTll, 1975). 

The lowest dose tested, 0.03 mg/kg, can be considered a LOAEL for rats subchronically exposed to sulfur mustard, with epithelial acanthosis and hyperplasia of the forestomach as the critical effect. Using this LOAEL, a human chronic RfD can be derived by adjusting the dose to a 7 day/week exposure protocol and then applying the result to the RfD methodology. Dose adjustments for discontinuous exposure can be made as follows female rats were gavaged 5 times/week for 15 weeks (75 days), total... 

In the absence of human or animal oral dose-response data, the relative potency approaches developed by Watson et al. (1989) and U.S. EPA (1991) are considered to be appropriate methods for estimating the tnmorigenic potency of sulfur mustard by the oral route of exposure. The oral slope factor derived by Watson et al. is approximately one order of magnitude less than the one derived from the relative potency estimated by U.S. EPA (1991). In the emerging area of relative potency analysis, a factor of 10 difference represents a good fit. There is no significant difference between the estimates of sulfur mustard carcinogenic potency relative to B(a)P pnblished by Watson et al. (1989) and U.S. EPA (1991). 

Human data regarding reproductive/developmental effects due to lewisite exposure are inconclusive because of confounding factors such as concurrent exposure to other agents such as sulfur mustards and incomplete exposure data. Yamakido et al. (1985) studied workers from the Okuno-jima (Japan) factory where mustard and lewisite were manufactured in the World War II era, and noted no evidence of agent-induced mutations. 

Studies of occupational exposures to sulfur mustard indicate an elevated risk of respiratory tract and skin tumors following long-term exposure to acutely toxic concentrations. Overall, several factors are important regarding the assessment of the carcinogenicity of sulfur mustard. Increased cancer incidence in humans appears to be associated only with exposures that caused severe acute effects, and occupational exposures tended to involve repeated exposures and repeated injury of the same tissues. Because the therapeutic use of the sulfur mustard analog nitrogen mustard is associated with an increased incidence of CML, the reports of CML in HD-exposed individuals appear to be relevant to the eareinogenicity of sulfur mustard. 

Smith, W.J., Cowan, F.M., Broomfield, C.A. (1991). Increased proteolytic activity in human epithelial cells following exposure to sulfur mustard. FASEB J. 5 A828. 

Smith, K.J., Smith, W.J. et al. (1998). Histopathologic and immunohistochemical features in human skin after exposure to nitrogen and sulfur mustard. Am. J. Dermatopathol. 20 22-8. 

More recent in vitro experiments, using human skin, have confirmed the presence of unhydrolyzed sulfur mustard in the lipophilic stratum comeum and the upper epidermis. Twenty-four hours post-exposure, the distribution ratio between the epidermis and the dermis has been determined at 62 to 38%. Ctulcott and colleagues (2000) also suggested that efforts to remove or neutralize the agent from these deposits might have a clinical benefit for the patient. 

Following two simultaneous cases of accidental human exposure to sulfur mustard, Smith et al. (2008) investigated the concentration of the cysteine-34 adduct to albumin and adducts to glutamic and aspartic acids of plasma proteins. In the case of a more severely exposed patient who required hospitalization, both adducts were detected over a 42 day period, though decreasing by approximately 75% towards... 

Smith, J.R., Capacio, B.R., Korte, W.D., Woolfitt, A.R., Barr, J.R. (2008). Analysis for plasma protein biomarkers following an accidental human exposure to sulfur mustard. J. Anal. Toxicol. 32 17-24. 

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