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TOXICOLOGICAL EVALUATION
last updated: 02/2005
(minor revision: 04/2006)

Chloroformic
acid methyl
ester

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Apart from the evaluation of chloroformic acid methyl ester (No. 36), thereare also TOXICOLOGICAL EVALUATIONS of chloroformic acid ethyl ester(No. 77), chloroformic acid propyl ester (No. 159) and chloroformic acidbutyl ester (No. 160), which may be consulted for comparison.
Summary and assessment
Chloroformic acid methyl ester is toxic following oral administration (LD50rat oral 40 to 313 mg/kg body weight). Upon inhalation, chloroformic acidmethyl ester is very toxic. LC50 values for the rat have been determined asapprox. 60, approx. 200 and approx. 208, and 450 mg/m³ following 4-hourexposure, and as approx. 345 to 480 mg/m³ following 1-hour exposure. Forthe mouse, the LC50 has been reported as 185 mg/m³ following 2-hour ex-posure. The high acute inhalation toxicity of chloroformic acid methyl ester,which is due to the chemical’s severe corrosiveness in conjunction with itshigh volatility, became strikingly apparent in inhalation hazard tests, inwhich all or the majority of rats died after only 3 minutes’ exposure to at-mosphere enriched or saturated with vapour at 20 °C. When applied to theskin, chloroformic acid methyl ester is systemically harmful to mildly toxic(LD50 rabbit dermal 7120 and > 3038 mg/kg body weight, rat dermal 894and approx. 1230 mg/kg body weight, and mouse dermal 1750 and 2200mg/kg body weight), but it causes leathery necrosis at the site of applica-tion. Dyspnoea, apathy, reeling, tremor, abnormal position, rough coat,salivation and poor general condition have been reported as signs of toxic-ity following oral administration. Following inhalation exposure the signs oftoxicity include, inter alia, mucous membrane irritation, closed eyes, red-dish ocular and nasal discharges, encrustations around the eyes and nose,escape behaviour and marked dyspnoea, due to the chemical’s corrosiveeffect. In addition, however, inhalation exposure is also associated withgeneral signs of severe intoxication similar to those seen after oral admini-stration. Necropsy findings have also been reported to include, in particu-lar, changes that were attributable to the chemical’s corrosive properties;inhalation exposure was associated with pulmonary haemorrhages, em-physema and oedema, inter alia, as well as markedly increased lung TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie weights and hydrothorax; oral administration resulted in blood in the stom-ach, haemorrhagic corrosive gastritis with sloughing and diffusely red-dened gastrointestinal mucosa; and intraperitoneal injection caused intra-abdominal adhesions. Furthermore, necropsies have frequently revealedacute dilatation and congestive hyperaemia of the heart, and a few studieshave demonstrated liver changes. Histological examinations following in-halation intoxication have shown severe degeneration of the nasalturbinate and tracheal mucosal epithelium, alveolar haemorrhages, erosionof bronchial and bronchiolar mucosal epithelium and increased permeabil-ity of the alveolar septa. The histopathological changes were mostly re-solved by 9 or 10 days after exposure in animals which had been exposedto levels of chloroformic acid methyl ester in the range of the LC50.
The toxic effects of chloroformic acid methyl ester following repeatedwhole-body inhalation exposure to concentration levels of 0 (controls), 0.4,2, 4 or 8 ppm (approx. 0 (controls), 1.6, 7.8, 15.7 or 31 mg/m³) are reportedin detail in a subchronic inhalation study with interim necropsies at 0.5, 2and 4 weeks (with the respective number of exposures totalling 3, 10, 20and 63) which was carried out in Wistar rats. Inhalation of chloroformic acidmethyl ester causes marked damage throughout the respiratory tract.
Damage is caused, in particular, to the ciliated respiratory epithelium andthe transitional epithelium of the nose and the ciliated epithelium at thebase of the epiglottis and the bronchioles. Less pronounced are the histo-pathological changes of the squamous epithelium and the cuboidal epithe-lium of the larynx and the ciliated respiratory epithelium of the trachea. Theolfactory epithelium remains normal. The epithelia mainly exhibit thickeningdue to hyperplasia and alterations in terms of squamoid metaplasia, andwith increasing number of exposures they also partly undergo keratinisa-tion. Mucus production is markedly enhanced initially; there is hypertrophyof the mucus-producing goblet cells but with prolonged exposure the cellsare displaced by the later predominant squamous epithelium. In the regionof the nasal cavity and the larynx purulent inflammation develops, whilst inthe alveolar and peribronchial regions prominent granulomatous inflamma-tion arises. In the deep regions of the lung there is loss of Clara cells,which normally fulfil a protective function. Due to inflammation of the lowerpart of the respiratory system absolute and relative lung weights are in-creased. The local manifestation of lesions and their severity depend to agreater extent upon the levels of exposure administered rather than the TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie number of exposures, i.e. the cumulative dose. Concentration levels of 4and 8 ppm (approx. 15.7 and 31 mg/m³) cause histopathological alterationsthroughout the entire respiratory tract after as few as 3 exposures, whereaslesions induced by 2 ppm (approx. 7.8 mg/m³) remain confined to the nasalcavity and the larynx even after 63 exposures. This indicates that the testsubstance is effectively removed from the air stream by the upper respira-tory tract up to a concentration of approx. 2 ppm. In addition to the histo-pathological changes discussed above, 24 or more exposures at 8 ppmcause some lethality, and exposure to levels ≥ 4 ppm depress body weightgain. The 8 ppm level causes clinical signs of toxicity which are indicativeof treatment-related irritation of the respiratory tract; signs were reported toinclude rubbing of snouts, sneezing and nasal crusts, intercurrent deathsbeing associated with abnormal breathing patterns and reduced generalstate. Substance-related macroscopic changes were confined to the ani-mals that underwent 8 ppm exposure for the entire duration of the study;they exhibited red foci in the lungs. DNA replication measured in the nasalcavity and larynx essentially reflected the histopathological changes. Withrespect to the assessment of minimal lesions, however, histological exami-nation was more sensitive than measurement of DNA replication. Notreatment-related toxicological changes were observed in organs otherthan the respiratory tract. Irrespective of the number of exposures, the noobserved adverse effect concentration (NOAEC) is reported as 0.4 ppm(1.6 mg/m³) for 3, 10, 20 and 65 exposures.
There is large agreement between the outcome of the subchronic inhala-tion study discussed above, in which Wistar rats were given interim ne-cropsies after 3, 10 and 20 exposures, and the findings of a 28-day inhala-tion study conducted in the Sprague-Dawley rat, according to which the noobserved effect concentration (NOEC) of chloroformic acid methyl ester is1.5 mg/m³ (approx. 0.4 ppm). Upon exposure to the next higher test con-centration of 4 mg/m³ (approx. 1 ppm), 1 out of 10 animals exhibited local-ised minor squamous metaplasia of the laryngeal epithelium, a lesion alsonoted in 1 out of 10 control animals. Comparison of the mortality data fromthe two studies reveals a striking increase in mortality with increasing con-centration levels. Whereas exposure to 8 ppm for a period ≥ 4 weeks in thesubchronic study with satellite groups resulted in the death of 4 out of 40(10%) animals, as many as 3 out of 10 (30%) animals died following expo-sure to approx. 9 ppm (35 mg/m³) in the fourth week of the subacute study.
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie In the rabbit, chloroformic acid methyl ester is corrosive to the skin andeye. Even a 1-minute skin exposure causes severe necrosis.
When conducted as a preincubation or standard plate incorporation assay,the Salmonella/microsome test on Salmonella typhimurium strains TA 98,TA 100, TA 1535 and TA 1538 reveals no mutagenic potential for chloro-formic acid methyl ester, either in the absence or presence of metabolicactivation. In the chromosome aberration test conducted in V79 cells of theChinese hamster, chloroformic acid methyl ester induced chromosomedamage upon metabolic activation with S-9 mix from Aroclor 1254-inducedrat liver. In the absence of metabolic activation, cells treated with chloro-formic acid methyl ester showed no increase in aberration rate.
In humans, poisoning by inhalation of chloroformic acid methyl ester is as-sociated with signs of severe irritation of the eyes and respiratory tract.
Depending on the level of exposure and frequently following an asympto-matic period, as is seen in phosgene poisoning, pulmonary oedema maydevelop and possibly result in death.
In the Federal Republic of Germany, the Commission for the Investigationof Health Hazards of Chemical Compounds in the Work Area (“MAK-Kommission”) of the Deutsche Forschungsgemeinschaft has established aMAK value (maximum workplace concentration) for chloroacetic acidmethyl ester on the suggestion of BG Chemie. It was set in the List ofMAK- and BAT Values 2004 at 0,2 ml/m³ (ppm, equivalent to 0,78 mg/m³).
Furthermore, chloroacetic acid methyl ester has been assigned to preg-nancy risk group C, i.e. substances for which “there is no reason to fear arisk of damage to the embryo or foetus when MAK and BAT values are ob-served“.
substance
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Synonyms, common and trade names
Carbonochloridic acid, methyl esterCarbonochloridsäuremethylesterChlorameisensäuremethylesterChlorkohlensäuremethylesterChlorocarbonic acid methyl esterFormic acid, chloro-, methyl esterMCFMethoxycarbonyl chlorideMethyl carbonochloridateMethylchlorameisensäureesterMethylchlorcarbonatMethylchlorformiatMethylchlorkohlensäureesterMethylchlormethanatMethyl chlorocarbonate 4 Structural
molecular
formulae
Physical and chemical properties
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Ca. 5 g/l (at 20 °C); hydrolysis tomethanol, hydrochloric acid and carbondioxide with a t½ value of ca. 15 minutes Hydrolysis constant: 14.1 x 10-4 (at35 °C); 5.6 x 10-4 (at 25 °C) ethanol, ethyl ether, benzene andtetrachloromethane Miscible with nearly all usual aproticsolvents 1 ml/m³ (ppm) ≙ 3.92 mg/m³1 mg/m³ ≙ 0.255 ml/m³ (ppm)(at 1013 hPa and 25 °C) TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Versatile intermediate used in the manufacture of e.g. dye components,peroxide compounds, herbicides, insecticides as well as pharmaceuticals(Böhm, 2001; Damle, 1992; BASF, 1981 a). Used as a solvent in the pho-tographic industry (Böhm, 2001).
Experimental results
Toxicokinetics and metabolism
Acute and subacute toxicity
Acute toxicity
The acute toxicity data for chloroformic acid methyl ester following oral, in-halation, dermal and intraperitoneal administration are shown in Table 1.
Table 1. Acute toxicity studies of chloroformic acid methyl ester
LD50; motor hyperactivity, de- n. d.
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Table 1. Acute toxicity studies of chloroformic acid methyl ester
LD50; dyspnoea, apathy, prone 14 days BASF, spastic gait, diarrhoea, poorgeneral condition; necropsyfindings: acute cardiac dilatationand congestive hyperaemia,clearly marked gastric vessels,glandular stomach diffuselyreddened with eschar formationin several cases, fluid intestinalcontents coat, salivation, poor generalcondition; necropsy findings inanimals that died intercurrently:heart: acute dilatation andcongestive hyperaemia,stomach: haemorrhagic areas,haemorrhagic gastritis withsloughing, intestine: diffusereddening of the intestinalmucosa, liver: occasionallymarks on the periphery of theliver lobules; terminal necropsyfindings: thickened forestomachwall, intra-abdominal adhesions mortality: 0/6 at 25 mg/kg body 14 days BASF, weight, hence classified astoxic; piloerection, apathy,dyspnoea, squatting position,reeling; necropsy findings inanimals that died intercurrently:general congestive hyperaemia,stomach, glandular stomach,severe reddening of the smallintestine and appendix, muchfluid in the stomach; terminalnecropsy was without findings TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Table 1. Acute toxicity studies of chloroformic acid methyl ester
impaired co-ordination, saliva-tion, crouching posture, de-pressed body weight gain;necropsy findings in animalsthat died intercurrently: heart:acute dilatation and congestivehyperaemia, lung: infarctoidcongestion, in part wet andbeefy, oedematous, marginalemphysema, hydrothorax inseveral cases, liver: occasional,mild, partly only focal peripheralhepatocellular steatosis; terminalnecropsy was without findings LC50; breathing difficulties as 14 days Hoechst, pressed body weight gain; ne-cropsy findings in animals thatdied intercurrently: dark red toblack discoloration of the lungs,pulmonary oedema, haemorrha-gic hydrothorax; terminal ne-cropsy findings: occasionallylungs with dark red foci; histolo-gical examination: damage to thebronchial epithelium, increasedpermeability of the alveolar septa Test in accordance with OECD guideline No. 403.
Rat, LC50; all other findings identical 14 days Hoechst, Test in accordance with OECD guideline No. 403.
Rat LC50; excitation, dyspnoea, nasal n. d.
findings: lung: haemorrhagicalveolar exudate, alveolar dila-tation, focal lymphoid infiltration,liver: slight cytoplasmic swellingand minor cytoplasmic vacuoli-sation, kidneys: occasionalinstances of vascular glomeru-lar destruction and luminal di-latation of the collecting tubules TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Table 1. Acute toxicity studies of chloroformic acid methyl ester
LC50; depressed body weight 14 days Battelle, or red tinted ocular and nasaldischarges; necropsy findings:lung discoloration, increase inlung weights; histological exami-nation of animals exposed to 430or 520 mg/m³ (satellite groups):4 and 24 hours after exposure:severe degeneration of the na-sal turbinate and tracheal muco-sal epithelium, alveolar hae-morrhages, erosion of bronchialand bronchiolar mucosalepithelium, by 9 or 10 days afterexposure microscopic respirato-ry tract lesions were resolvedbut regeneration of nasal muco-sal epithelium was incomplete LC50; all other findings identical 14 days Battelle, mortality: 9/10, sneezing, inter- 14 days Hoechst, whimpering and crackling brea-thing noises, ruffled fur, narrowor closed palpebral fissures,squatting posture, prone position,drowsiness, reeling movements,uncoordinated gait, weakenedreflexes, depressed body weightgain; necropsy findings: dark redfoci on the lungs and dark reddiscoloration of the lungs, ap-pearance of frothy watery liquidupon opening the lung, reddishwatery liquid in the abdominalcavity; terminal necropsy ofsurvivors was without findings mortality: 12/12; vigorous escape 14 days BASF, TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Table 1. Acute toxicity studies of chloroformic acid methyl ester
mortality: 10/10; all animals died n. d.
brown foci on the outer edges ofthe lungs; histological examina-tion: haemorrhages of the par-enchymal and pleural capillaries Acute inhalation hazard test (limit test) in accordance with OECD guideline No. 403.
Rat mortality: 11/12, 5/6 and 6/6, n. d.
acute bilateral dilatation of theheart, congestive hyperaemia,lung congestion with severeoedema and moderate acuteemphysema LC50; excitation, dyspnoea, 14 days Gurova et necropsy findings: lung:haemorrhagic alveolar exudate,alveolar dilatation, focallymphoid infiltration, liver: slightcytoplasmic swelling and minorcytoplasmic vacuolisation,kidneys: occasional instances ofvascular glomerular destructionand luminal dilatation of thecollecting tubules LD50; dyspnoea, apathy, reeling, 14 days BASF, signs of primary irritation after24 hours and leathery necrosisafter 4 days; necropsy findingsin animals that diedintercurrently: heart: acute rightventricular dilatation and acutecongestive hyperaemia, lung: inpart severe extensivehaemorrhages (wet and beefyareas); terminal necropsy ofsurvivors was without findings TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Table 1. Acute toxicity studies of chloroformic acid methyl ester
LD50; dyspnoea, slight apathy; 14 days BASF, LD50; dyspnoea, apathy, reeling 14 days BASF, When administered orally, chloroformic acid methyl ester proved to be toxicin rat studies, with LD50 values ranging from 40 to 313 mg/kg body weight(BASF, 1975, 1981 b; Gurova et al., 1977; Industrial Bio-Test, 1975; Vernotet al., 1977). Oral LD50 values were published as 40 and 67 mg/kg bodyweight for mice and 140 mg/kg body weight for guinea pigs (Plzak andDoull, 1969; Gurova et al., 1977). Upon inhalation, chloroformic acid methylester was very toxic. LC50 values for the rat were determined as 60, ap-prox. 200 and approx. 208, and 450 mg/m³ following 4-hour exposure(BASF, 1980; Hoechst, 1986 a; Gurova et al., 1977), and as approx. 345 to480 mg/m³ following 1-hour exposure (Vernot et al., 1977; Battelle, 1981).
The high acute inhalation toxicity of chloroformic acid methyl ester, which isdue to the chemical’s high volatility, became strikingly apparent in inhala-tion hazard tests, in which all or the majority of rats died after only 3 min-utes’ exposure to atmosphere enriched or saturated with vapour at 20 °C(BASF, 1975, 1981 c; Hoechst, 1985). For the mouse, the LC50 was re-ported as 185 mg/m³ following 2-hour exposure (Gurova et al., 1977).
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie When applied to the skin, chloroformic acid methyl ester was of low sys-temic toxicity (LD50 rabbit dermal 7120 and > 3038 mg/kg body weight, ratdermal 894 and approx. 1230 mg/kg body weight, and mouse dermal 1750and 2200 mg/kg body weight), but it caused leathery necrosis at the site ofapplication, where reported (BASF, 1975, 1981 d; Industrial Bio-Test, 1975;Gurova et al. 1977; Vernot et al., 1977). Following intraperitoneal admini-stration to mice the LD50 was approx. 11 mg/kg body weight. However, thestudy in question was carried out with chloroformic acid methyl ester inaqueous solution, for which reason it is highly likely that the chemical hadundergone hydrolysis (see also Section 5.6). Dyspnoea, apathy, reeling,tremor, abnormal position, rough coat, salivation and poor general condi-tion, inter alia, were described as signs of toxicity following oral administra-tion (BASF, 1975, 1981 b, 1990). Following inhalation exposure the signsof toxicity included mucous membrane irritation, closed eyes, reddish ocu-lar and nasal discharges, encrustations around the eyes and nose, escapebehaviour and marked dyspnoea, due to the chemical’s corrosive effect. Inaddition, however, inhalation exposure was also associated with generalsigns of severe intoxication, such as depressed body weight gain, poorgeneral condition, motor disorders and impaired autonomic reactions(BASF, 1980, 1981 c; Hoechst, 1985, 1986 a; Battelle, 1981; Gurova et al.,1977). Necropsy findings also, in particular, included changes that wereattributable to the chemical’s corrosive properties; inhalation exposure wasassociated with pulmonary haemorrhages, emphysema and oedema inconjunction with markedly increased lung weights and hydrothorax; oraladministration resulted in blood in the stomach, haemorrhagic corrosivegastritis with sloughing and diffusely reddened gastrointestinal mucosa;and intraperitoneal injection caused intra-abdominal adhesions. Further-more, necropsies frequently revealed acute dilatation and congestive hy-peraemia of the heart, and a few studies demonstrated liver changes(BASF, 1975, 1980, 1981 b, c, 1990; Hoechst, 1985, 1986 a; Battelle,1981; Gurova et al., 1977). Histological examinations following acute inha-lation intoxication showed severe degeneration of the nasal turbinate andtracheal mucosal epithelium, alveolar haemorrhages, erosion of bronchialand bronchiolar mucosal epithelium and increased permeability of the al-veolar septa (Hoechst, 1986 a; Battelle, 1981). The histopathologicalchanges were mostly resolved by 9 or 10 days after exposure in animalswhich had been exposed to levels of chloroformic acid methyl ester in therange of the LC50 (Battelle, 1981).
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie The acute toxicity data which are available only from secondary sources(LC50 for 1-hour exposure 450 mg/m³ without any indication of the speciestested (Damle, 1992), LD50 mouse intraperitoneal 40 mg/kg body weight(RTECS, 2001), and mortality in cats given as 3 out of 3 following 30 min-utes’ exposure to 1500 mg/m³ (Lazarev, 1963)) are suitable only to a lim-ited extent for the assessment of the chemical's acute toxicity, as essentialdetails concerning study conduct, species and data analysis are partly orcompletely lacking in those sources.
Subacute toxicity
The toxic effects of chloroformic acid methyl ester (99.2% pure) followingsubacute administration were investigated in male and female Sprague-Dawley rats in an inhalation study conducted in accordance with OECDguideline No. 412. Groups of 5 males and 5 females were exposed to chlo-roformic acid methyl ester at nominal concentration levels of 0 (controls),0.5, 1.5, 4.0, 12.0 or 35.0 mg/m³ for 6 hours per day, 5 days per week for 4weeks (whole-body vapour exposure). The analysed concentration levelswere 0 (controls), 0.52, 1.48, 3.94, 12.14 and 34.46 mg/m³. Treatment-related deaths occurred in 2 males and one female from the top concentra-tion group in the final week of the study after they had previously exhibitedmarked body weight loss. The top concentration group showed clinicalsigns of toxicity which, in the investigators’ interpretation, were attributableto the irritant effect of the chemical; these included hunched posture,blinking of the eyelids, noisy nasal breathing and, during the third week ofthe study, rapid breathing pattern. Animals exhibited temporary reduction infood consumption in association with reduced body weight gain, with someanimals also showing weight loss at later stages of the study. Significantand toxicologically relevant changes in haematological parameters assigns of haemoconcentration were observed in respect of packed cell vol-ume, haemoglobin and red cell numbers, and increased neutrophil countswere associated with inflammatory lesions seen in the respiratory tract.
Furthermore, total protein (in males only), globulin and cholesterol levelswere increased while albumin and the albumin/globulin ratio were de-creased. At necropsy, the lungs of 3 out of 3 males and 4 out of 4 femalesfailed to collapse upon thoracotomy and were congested in 1 out of 4 fe-males and 1 out of 3 males, and enlargement of the tracheobronchial and TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie mediastinal lymph nodes was noted in 3 out of 3 males and 3 out of 4 fe-males. Lung weights were increased in both sexes. Histological examina-tion revealed changes of the nasal mucosa (acute exudative sinusitis) in 4out of 5 males and 5 out of 5 females; minimal squamous metaplasia withminor epithelial erosion and focal inflammation of the larynx in 3 out of 5males and 4 out of 4 females; inflammatory changes and minimal epithelialhyperplasia of the trachea in 1 out of 5 males; pneumonia together with in-tra-alveolar exudation and alveolar macrophage aggregation in all malesand females, and additionally oedema, congestion, bronchiolitis, squamousmetaplasia of terminal bronchiolar epithelium with focal necrosis in someanimals and granulomatous lesions in 1 out of 5 females. In the group ex-posed to the second-highest concentration, 12.14 mg/m³, only 1 out of 5males exhibited noisy nasal breathing during the second week of the study.
All other animals from this concentration group showed no clinical signs oftoxicity. Body weight gain, food consumption, haematological and bio-chemical parameters and necropsy findings were normal in the animalsfrom the group exposed to the second-highest concentration. Histopatho-logical changes in the form of exudative sinusitis were noted in 1 out of 5females and in the form of localised minor squamous metaplasia of the la-ryngeal epithelium in 2 out of 5 males and 1 out of 5 females. Similarchanges of the laryngeal epithelium were also observed in one male fromthe intermediate concentration group and one female from the controlgroup. Nominal concentrations of 0.5 and 1.5 mg/m³ (analytical concentra-tions of 0.52 and 1.48 mg/m³) produced no effects (HRC, 1992).
The concentration levels used in the 28-day inhalation study describedabove (HRC, 1992) were identified on the basis of the results of a 5-dayrange-finding study in which groups of 5 male and 5 female Sprague-Dawley rats were exposed to chloroformic acid methyl ester levels of 0(control), 7.5, 24 or 75 mg/m³ (analytical concentrations of 0 (control), 7.5,24 and 74 mg/m³) and 7.5 mg/m³ was tolerated by the animals without ab-normal findings. The clinical signs of toxicity observed during exposures in-cluded blinking of the eyelids, licking the inside of the mouth, ruffled fur,sneezing in the top and intermediate dose groups, and irregular breathing,which was confined to the top group. In between exposures, the high-concentration males sneezed and exhibited noisy nasal breathing. Re-duced food and water consumption was associated with body weight lossin the animals from the top concentration group. At necropsy 3 days after TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie the end of exposure, the lungs failed to collapse in 1 out of 5 intermediate-dose males and in 3 out of 5 males and 5 out of 5 females from the topconcentration group. The lungs of 1 out of 5 intermediate-dose males and5 out of 5 males and 1 out of 5 females from the top concentration groupexhibited petechial bleeding. All females from the top concentration grouphad increased lung weights. Organ weights could not be evaluated formales due to an error occurring during necropsy. Histological examinationrevealed inflammatory and erosive mucous membrane lesions in the nose,larynx, trachea and lungs (bronchiolitis, pneumonia) in animals from the topconcentration groups as well as focal epithelial hyperplasia of the nasalmucosa in animals from the intermediate and top concentration groups.
Comparison of the histopathological findings for a satellite group examinedimmediately after the end of exposure to those obtained for animals whichwere examined 3 days after the end of exposure demonstrated clear signsof regeneration and repair of epithelial lesions. There were no findings atthe lowest concentration level of 7.5 mg/m³ (HRC, 1992).
Chloroformic acid methyl ester was investigated together with 108 otherchemicals in an exploratory subacute inhalation study. Groups of 4 maleand 4 female Alderly Park SPF rats weighing approx. 200 g underwentwhole-body exposure to chloroformic acid methyl ester at concentrationlevels of 20, 5 or 1 ppm (approx. 78.4, 19.6 and 3.92 mg/m³) for 6hours/day, 5 days/week over a period of 3 weeks. There were no concur-rent controls in the study. Assessments included clinical signs of toxicity,body weight gain, necropsy and histological examination of at least thelungs, liver, kidneys, spleen and adrenal glands. Clinical chemistry andhaematology tests were probably not carried out in animals treated withchloroformic acid methyl ester. Exposure to 20 ppm chloroformic acidmethyl ester caused nose irritation, respiratory difficulty, lethargy, poorgeneral condition and weight loss. At necropsy, the lungs were distendedand haemorrhagic. Histological examination revealed areas of consolida-tion and collapse, oedema and haemorrhage in the lungs, and congestionof the kidneys. Exposure to 5 ppm only produced signs of irritation andlethargy, whilst exposure to 1 ppm was tolerated by rats without remark-able findings (no further details; Gage, 1970).
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Skin and mucous membrane effects
The acute skin irritancy of undiluted chloroformic acid methyl ester (puritynot specified) was tested in rabbits. The chemical was applied to the dorsalskin for 1, 5 or 15 minutes or 20 hours, or to the skin of the ear for 20hours. The observation period was 8 days. As shown in Table 2 below,even a 1-minute exposure to chloroformic acid methyl ester caused severereddening of the area of exposure and beyond, severe oedema and, sub-sequently, severe leathery necrosis which extended beyond the area ofexposure. Chloroformic acid methyl ester was evaluated as corrosive bythe investigators (BASF, 1975).
Table 2. Irritant effects of chloroformic acid methyl ester on the rabbit
skin and their dependence on the duration of exposure
(based on BASF, 1975)
severe reddening of the area of exposure severe necrosis, leathery andand beyond, very severe oedema severe reddening of the area of exposure severe necrosis, leathery andand beyond, partly livid, very severe oedema extending beyond the area of minutes slight necrosis, surrounded by slight severe necrosis, leathery and slight necrosis, surrounded by severe severe necrosis, leathery andreddening and severe oedema partly slight necrosis, partly severe partly slight necrosis, anaemic,reddening and severe oedema In order to validate a test method allowing more differentiated classificationof a chemical as corrosive or irritating to the skin, a screening study wasconducted which also included chloroformic acid methyl ester. Groups of 6New Zealand white rabbits underwent a single 1-hour or 4-hour exposureof the depilated uninjured skin of the flank to gauze pads impregnated with0.5 ml undiluted chloroformic acid methyl ester (purity not specified) underboth occlusive and semi-occlusive conditions. The 4 exposure variantswere tested in parallel in each animal. The effects were assessed after 1,24, 48 and 72 hours and after 7 days in accordance with OECD guidelineNo. 404. All 4 types of exposure produced extensive areas of discolouredskin (grey-white, yellowish brown) and necrosis as well as encrustation and TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie induration at the sites of application. After occlusive application, in particu-lar, there was also reddening beyond the sites of application. Chloroformicacid methyl ester was evaluated as corrosive to the skin in all 4 substudies,i.e. after 1-hour and 4-hour exposure under both semi-occlusive and occlu-sive conditions (Hoechst, 1982 b; Potokar et al., 1985).
Another skin irritation test with chloroformic acid methyl ester was con-ducted in 3 New Zealand white rabbits which received 3-minute applica-tions of the test substance to the depilated intact skin of the flank under oc-clusive as well as semi-occlusive conditions. Examinations were carried outin accordance with OECD guideline No. 404. Damage reached deep intothe skin of the rabbits. The sites of application displayed white-grey and/orbrown discoloration, accompanied by necrosis and/or very marked or se-vere oedema as well as erythema together with eschar formation and en-crustation. The treated flanks were reddened beyond the area of applica-tion in animals which underwent occlusive exposure. In general, findingswere somewhat less marked in animals receiving semi-occlusive treatmentthan in those with occlusive treatment. Chloroformic acid methyl ester wasevaluated as severely irritating to corrosive (Hoechst, 1982 b).
In a further skin test in albino rabbits, a skin irritation index was determinedas 110 out of a maximum score of 110, and hence chloroformic acid methylester was evaluated as extremely irritating, and corrosive (no further de-tails; Industrial Bio-Test, 1975).
In contradiction with the above-mentioned findings (BASF, 1975; IndustrialBio-Test, 1975; Potokar et al., 1985) according to which chloroformic acidmethyl ester is corrosive to the skin, another report claimed, without givingdetails, that single application of undiluted chloroformic acid methyl ester ora solution of the chemical in oil to the skin of mice, rats and rabbits pro-duced no signs of irritation whatsoever. Reportedly, the only signs seenafter 3 or 4 applications were mild hyperaemia and subsequent mild pig-mentation (Gurova et al., 1977). As essential details concerning experi-mental design and assessment of effects (e.g. duration of exposure, modeof application, scope and time points of examination) are lacking, the studyis unsuitable for evaluating the skin irritancy of chloroformic acid methylester.
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Chloroformic acid methyl ester exhibited severely corrosive effects to theeye in a rabbit study. One hour following instillation of 50 µl chloroformicacid methyl ester (purity not specified) into the rabbit eye, findings includedmild reddening, severe oedema, severe clouding of the eye, white nictitat-ing and mucous membranes, and 24 hours upon instillation vascular injec-tion and greasy films were observed in addition. At 8 days, corrosive ef-fects were even more manifest, with slight reddening, severe oedema andsevere clouding, corrosion, iritis, staphyloma, purulent discharge, scars andencrustations of the eyelids being observed. Negative controls treated withsodium chloride were without abnormal findings at all scheduled examina-tions (BASF, 1975).
In a further test for mucous membrane effects in albino rabbits, chlorofor-mic acid methyl ester was evaluated as extremely irritating, and corrosive.
An irritation index of 8.0 out of a maximum score of 8.0 was determined (nofurther details; Industrial Bio-Test, 1975).
Without providing further details, one source reports that a single instillationof an oily formulation of chloroformic acid methyl ester into the eyes of rab-bits produced severe inflammation, purulent discharge and general intoxi-cation (Gurova et al., 1977). As essential details concerning experimentaldesign and assessment of effects (e.g. concentration of chloroformic acidmethyl ester in the formulation tested, duration of exposure, scope and timepoints of examination) are lacking, the study is unsuitable for evaluating theirritating effects of chloroformic acid methyl ester on mucous membranes.
Sensitisation
Subchronic and chronic toxicity
The toxic effects of chloroformic acid methyl ester following subchronic ex-posure were investigated in an inhalation study in Wistar rats which wasconducted in accordance with OECD guideline No. 413, EPA TSCA guide-line 40 CFR § 798.2450 and EC Directive 87/302/EEC. Groups of 10 malesand 10 females per concentration level underwent whole-body exposure tochloroformic acid methyl ester at nominal levels of 0 (control), 0.4, 2, 4 or 8 TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie ppm (approx. 0 (control), 1.6, 7.8, 15.7 or 31 mg/m³). Test concentrationswere selected taking into consideration the findings from the subacute in-halation study in the Sprague-Dawley rat discussed above (HRC, 1992;see Section 7.2). Mean concentration levels as determined by analysiswere 0 (control), 0.40, 2.15, 3.98 and 7.83 ppm (approx. 0 (control), 1.6,8.4, 15.6 and 30.7 mg/m³). The chloroformic acid methyl ester used for ex-posure was > 99.4% pure at the beginning of the study; upon reanalysis atthe end of the study purity was found to be 98.5%. In addition to the groupsof animals which underwent a total of 65 exposures lasting 6 hours/workingday over the entire study duration of 92 days, satellite groups of 10 malesand 10 females for interim necropsies after 3, 10 or 20 exposures were in-cluded for each test concentration and scheduled time point of examinationand treated under identical conditions. Per group, the nasal cavity and lar-ynx of 4 females pretreated with 5-bromo-2ˈ-deoxyuridine were studied bydetermining DNA replication as a measure of cell proliferation. No haema-tology or clinical chemistry studies were carried out. Four male rats ex-posed to 8 ppm died, the deaths being recorded after 24, 32, 36 and 41exposures. Clinical signs of toxicity were confined to the top concentrationgroup and indicated treatment-related irritation of the respiratory tract;signs included rubbing of snouts, sneezing, nasal crusts and in the animalswhich subsequently died, abnormal breathing patterns and reduced gen-eral state. Body weight change exhibited slight reduction in males from theintermediate and top concentration groups. Slight yet statistically significantdecreases in absolute body weights were seen, but only in males of topconcentration group which were sacrificed after 3 exposures or at the endof the study. Substance-related macroscopic changes were confined to theanimals that underwent 8 ppm exposure for the entire duration of the study;they exhibited red foci in the lungs. Animals from this concentration groupwhich died intercurrently exhibited emphysema and/or multifocal discolora-tion of the lungs. Animals from the top concentration group, except forthose sacrificed for the first interim necropsy after 3 exposures, displayedincreases in relative and absolute lung weights. All other organ weightsshowed no treatment-related or toxicologically relevant changes whencompared with the controls. Histopathological changes were restricted tothe respiratory tract. An overview of the frequency and severity of the le-sions observed in various parts of the respiratory tract is provided in Table3 below.
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Table 3. Histopathological findings and increased cell proliferation
rates1 in the Wistar rat following 3, 10, 20 or 65 whole-body
exposures to chloroformic acid methyl ester (subchronic inhalation
study with interim necropsies at 0.5, 2 and 4 weeks), based on BASF
Determination of DNA replication following 5-bromo-2ˈ-deoxyuridine pretreatment Histopathological changes of the respiratory tract were noted after only
three exposures to levels of chloroformic acid methyl ester ≥ 2 ppm. Al-
terations of the nasal cavity
consisted in squamous epithelial metaplasia
and focal or diffuse hyperplasia of the ciliated respiratory epithelium and
the transitional epithelium. Associated with enhanced mucus production
was hypertrophy of the mucus-producing goblet cells but with prolonged
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie exposure the cells were displaced by the later predominant squamous
epithelium. By the end of the study the squamoid, greatly thickened transi-
tional epithelium additionally exhibited marked surface keratinisation. Be-
ginning at the transitional epithelium but by the end of the study also af-
fecting the respiratory epithelium, there was purulent inflammation which
was associated with necrotic cells sloughing off. DNA replication in the res-
piratory epithelium of animals treated at 8 ppm depended upon the dura-
tion of exposure and was found to be slightly increased following 3 expo-
sures, relative to controls, whilst respective increases were 2.5 and 4.5-fold
after 10 and 20 exposures and 33-fold at the end of the study. Animals ex-
posed to 2 or 4 ppm were noted to have significant increases in DNA repli-
cation at the third interim necropsy and thereafter, attaining 7.9-fold and
17.6-fold values relative to controls by the end of the study. The enormous
increase in DNA replication was explained by the investigators in the con-
text of markedly enhanced cell renewal rates in squamoid epithelium. In the
transitional epithelium, DNA replication was found to be increased after 3
or more exposures in the concentration groups treated at 8 or 4 ppm and
after 20 or more exposures in the concentration group treated at 2 ppm.
Strikingly, there was a drop in proliferation rate of the transitional epithe-
lium in the front portion of the nasal cavity at the end of the study, a finding
which the investigators explained in terms of increasing keratinisation of
the tissue. Squamous and olfactory epithelia of the nasal cavity were with-
out significant findings. Alterations of the larynx noted in the region of the
ciliated epithelium at the base of the epiglottis consisted in squamous
metaplasia with minimal to moderate hyperplasia and partly purulent in-
flammation of the submucosa and were found to be concentration-
dependent at the first and later interim necropsies in animals from the up-
per three concentration groups. Squamous epithelial metaplasia was mul-
tifocal after 3 treatment days and exhibited diffuse extension after 10
treatment days. As the study progressed, the cells of the top layer of the
ciliated epithelium became increasingly flatter and showed signs of kerati-
nisation. Necrotic cells were found after 10 and 20 exposures but they dis-
appeared by terminal necropsy after 63 exposures, a finding which the in-
vestigators considered to be due to protective squamous cell layers. Nor-
mally not keratinised, the squamous epithelium of the larynx was inflamed,
hyperplastic and keratinised and exhibited single necrotic cells in the upper
three concentration groups at the end of the study. The same alterations
were also seen in the top concentration group after 3 exposures. The top
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie concentration group exhibited minimal to moderate hyperplasia of the cu-
boidal epithelium of the larynx at all time points of investigation. Increases
in DNA replication observed in the ciliated epithelium in the three upper
concentration groups were 2.3 to 31.1-fold relative to controls up to the
third interim necropsy, while in the squamous epithelium they were 5 and
8.3-fold in the two upper concentration groups up to terminal necropsy. A
slight but significant increase in DNA replication was observed in the cu-
boidal epithelium of the 8 ppm animals after 3 treatment days and at the
end of the study. Alterations of the trachea were confined to the two up-
per concentration groups. They occurred in a concentration-dependent
manner after 3 or more exposures and consisted in squamous metaplasia
and hypertrophy of the goblet cells, which was associated with increased
production of mucus. Additionally, the top concentration group exhibited fo-
cal epithelial hyperplasia. Alterations of the lungs were confined to the
two upper concentration groups, similarly to the histopathological altera-
tions of the trachea. After 3 exposures, hyperplastic and metaplastic
changes in the pulmonary epithelium of animals exposed to 8 ppm were
observed in the terminal bronchioles, particularly at the junctions to the al-
veolar ducts, the alterations expanding to all bronchioles including the
segmental bronchioles by the end of the study. Clara cells, which fulfil a
protective function, had disappeared. The respiratory epithelium was either
extremely flattened or hyperplastic. The alveoles and the peribronchial tis-
sue exhibited prominent granulomatous inflammation, which in part also
extended focally into the parenchyma. Some animals had large accumula-
tions of mucus in the alveolar ducts and bronchioles. Animals treated at 4
ppm showed marked histopathological changes of the lung only at terminal
necropsy after 65 exposures. In summary, inhalation of chloroformic acid
methyl ester by rats caused prominent morphological alterations in the cili-
ated respiratory epithelium and the transitional epithelium of the nose as
well as in the ciliated epithelium at the base of the epiglottis and in the
bronchioles. Less pronounced were the histopathological changes of the
squamous epithelium and the cuboidal epithelium of the larynx and the cili-
ated respiratory epithelium of the trachea. Alterations of the epithelia
mainly consisted in hyperplasia and squamous metaplasia. DNA replication
measured in the nasal cavity and larynx essentially reflected the histo-
pathological changes. With respect to the assessment of minimal lesions,
however, histological examination appeared to be more sensitive than
measurement of DNA replication. Concentrations of 8 and 4 ppm caused
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie lesions throughout the entire respiratory tract, whereas with 2 ppm lesionswere restricted to the nasal cavity and the larynx, irrespective of the num-ber of exposures. This indicates that the test substance is effectively re-moved from the air stream by the upper respiratory tract up to a concentra-tion of approx. 2 ppm. The concentration-response relationship was drivenmainly by the concentrations used for exposure rather than the cumulativedose. Irrespective of the number of exposures, the no observed adverseeffect concentration (NOAEC) was 0.4 ppm (1.6 mg/m³) for 3, 10, 20 and65 exposures (BASF, 1999).
In a study with exposure for up to 4 months, male mice were exposed tochloroformic acid methyl ester at levels of 0 (controls), 0.185, 0.64 or 2.06mg/m³, and male rats were exposed to chloroformic acid methyl ester at 0(controls), 0.197, 0.72 or 2.15 mg/m³. Essential details concerning experi-mental design and scope of examination, e.g. strains of animals used,numbers of animals per group, determination of concentrations, mode andduration of exposure, are lacking. Histological examination of the animalswhich died intercurrently and those sacrificed at the end of the study waswithout findings in the low concentration group. The intermediate studygroups displayed swelling of the bronchial epithelium; the liver and kidneyswere normal. Histological findings in the high exposure groups includedthickening of the alveolar septa, lymphoid infiltration of the bronchi, vacu-olisation of liver cells and lesions in the proximal tubular epithelium of thekidney. There are no indications as to whether examinations were not car-ried out in both species, nor are any data given regarding the incidence orseverity of the findings. Without giving any further information regarding thenature, severity or assignment of findings to exposure levels, additionalfindings were reported as changes in nerve-muscle conduction, body tem-perature, respiratory rate, red blood cell count and osmotic stability oferythrocytes, reticulocyte count, bromosulphophthalein test, organ weightsof the lungs, heart, liver, kidneys, spleen and adrenal glands as well as thevitamin C levels in individual organs (Gurova et al., 1977). As essentialdetails concerning experimental design and assessment of effects arelacking and documentation as a whole is inadequate, the study is unsuit-able for evaluating the chronic toxicity of chloroformic acid methyl ester.
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Genotoxicity
7.6.1 In vitro
In the Salmonella/microsome test carried out in accordance with OECDguideline No. 471, chloroformic acid methyl ester (99.2% pure) was devoidof mutagenicity both in the absence and presence of metabolic activation(S-9 mix from Aroclor 1254-induced rat liver). The study was conducted asa preincubation test in which Salmonella typhimurium strains TA 98, TA100 and TA 1537 were incubated with chloroformic acid methyl ester atconcentrations ranging from 0.0005 to 1.0 µl/plate, Salmonella typhimuriumstrain TA 1535 being exposed to chloroformic acid methyl ester levels from0.0005 to 5.0 µl/plate. Ethanol served as the solvent. In the presence ofS-9 mix, concentration levels ≥ 0.5 µl/plate exhibited bacteriotoxicity whilein the absence of metabolic activation even lower concentrations ≥ 0.01µl/plate were toxic. Incubation of Salmonella typhimurium strains with chlo-roformic acid methyl ester did not result in any significant increase in re-vertant counts. Tests employing the positive controls 2-aminoanthracene,N-methyl-Nˈ-nitro-N-nitrosoguanidine, 4-nitro-o-phenylenediamine, 9-amino-acridine chloride monohydrate and dimethylcarbamyl chloride gave the ex-pected results (BASF, 1988 b).
A further Salmonella/microsome assay using Salmonella typhimuriumstrains TA 98, TA 100, TA 1535 and TA 1537 with and without metabolicactivation (S-9 mix from Aroclor 1254-induced rat liver) also did not dem-onstrate mutagenic potential of chloroformic acid methyl ester at levelsfrom 1 to 100 µg/plate. The test was carried out as a standard plate incor-poration test with 3 plates per concentration. There were no increases inrevertant counts up to the highest test concentration of 100 µg/plate. A pre-liminary study had demonstrated bacteriotoxicity at 333 µg/plate both withand without metabolic activation. The positive controls sodium azide,4-nitro-o-phenylenediamine and 2-aminoanthracene and the negative con-trol methanol (solvent) yielded the expected results (LMP, 1985).
These findings confirmed the results of an earlier Salmonella/microsomeassay carried out in Salmonella typhimurium strains TA 98, TA 100, TA1535 and TA 1537 both in the absence and presence of metabolic activa-tion (S-9 mix from Aroclor 1254-induced rat liver). Two plates per concen-tration level were incubated with chloroformic acid methyl ester at 0 (nega- TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie tive control ethanol), 0.25, 0.1, 0.02 or 0.004 µl/plate. No details were re-ported regarding the purity of the test substance or the bacteriotoxicityseen at the concentrations tested. Chloroformic acid methyl ester did notincrease revertant counts. As expected, the positive controls 2-acetyl-aminofluorene, benzo(a)pyrene, β-naphthylamine, neutral red, 4-nitro-o-phenylenediamine and streptozotocin induced marked increases in rever-tant counts (Hoechst, 1977).
In the chromosome aberration test conducted in V79 cells of the Chinesehamster, chloroformic acid methyl ester induced chromosome damageupon metabolic activation with S-9 mix from Aroclor 1254-induced rat liver.
Tests were carried out both with and without metabolic activation at chlo-roformic acid methyl ester levels of 0.1, 1.0 and 2.5 µl/ml. Cells were pre-pared at 7 (top concentration only), 18 or 28 (top concentration only) hours.
For each scheduled time point of assessment, 400 metaphases werescored per concentration. In the absence of metabolic activation, cellstreated with chloroformic acid methyl ester showed no increase in aberra-tion rate. In the presence of metabolic activation, cells prepared after 7 or28 hours were found to have markedly increased aberration rates relativeto the negative control (solvent), regardless of whether gaps were includedor not. Cells prepared at 18 hours showed no increase in aberration rate.
The respective mitotic indices for the top concentration observed at thethree scheduled time points of preparation were 38, 80.6 and 80.5%. Theinvestigators explained the different results obtained for the individual timepoints of assessment as temporary changes in cell cycle phases in thedamaged cells. Tests with the positive controls ethylmethane sulphonateand cyclophosphamide yielded the expected results. The investigatorsconcluded that in this in-vitro cytogenetics study in V79 cells chloroformicacid methyl ester was mutagenic in the presence of metabolic activation(LMP, 1986).
7.6.2 In vivo
Carcinogenicity
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie Reproductive toxicity
Effects on the immune system
Neurotoxicity
Other effects
Experience in humans
Thiess and Hey (1968) reported a total of 14 cases of human poisoning byinhalation of chloroformic acid methyl ester, including one with fatal out-come. The fatal poisoning (following exposure at a level of approx. 40000ppm (approx. 156800 mg/m³), as estimated from the air flow, temperatureand physical constants) was the result of grossly negligent disregard ofsafety regulations when cleaning a container for chloroformic acid methylester. As an immediate response to inhalation of chloroformic acid methylester, the exposed worker developed a strong urge to cough, shallow res-piration, retrosternal pain, dyspnoea, tachycardia, irritation of the conjuncti-vae and severe restlessness. Upon admission to hospital after first-aidtreatment at the company’s medical department, the following findingswere noted: good general condition, marked conjunctivitis, urge to cough,no cyanosis, no marked dyspnoea at rest, slightly diminished vesicularbreathing and occasional bronchial rales, normal findings for the heart, cir-culation, abdominal organs and CNS and normal temperature. The thoracicx-ray exhibited diffuse, confluent foci over both mid and lower lung fieldsand the beginning of pleural effusion on the right side. Despite intensivetherapy (cortisol, antibiotics, circulatory support, sedatives, oxygen tent)the patient died of pulmonary oedema four days after inhalation exposure TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie to chloroformic acid methyl ester. In the remaining 13 cases, which theauthors considered trivial poisonings, the signs included lacrimation to-gether with irritation of the conjunctivae and in some cases laryngitissymptoms with dry cough. The reported signs were completely reversiblewithin 1 to 2 hours. The general findings – including thoracic x-rays – wereunremarkable (Thiess and Hey, 1968; Hey and Thiess, 1968).
In one case of accidental exposure to chloroformic acid methyl ester aworker inhaled no more than two or three breaths of the gas. Approxi-mately one hour later, he presented at the company’s medical departmentcomplaining of a slight burning of the eyes and a mild urge to cough. Pul-monary auscultation was largely unremarkable except for the presence of avery occasional rhonchus over the upper fields on both sides. The workerreceived symptomatic treatment and was completely free of symptoms by 6hours after exposure. The next morning, coughing and slight dyspnoea aswell as rhonchus and dry rale over the entire lung developed. Examinationby x-ray two days after exposure revealed diffuse increase in markingsover the right lower lung field. Following therapy with antibiotics, corticoids,cough medicines and bed rest, lung auscultation was normal one week af-ter exposure. In the subsequent period of time, however, a severe urge tocough repeatedly occurred, particularly in the mornings, after periods com-pletely free of symptoms. At a later point in time (no precise details given),comprehensive examination at a lung hospital revealed no pathologicalfindings. The author particularly emphasised the long latency period be-tween exposure and the manifestation of severe clinical signs and symp-toms following intoxication with chloroformic acid methyl ester (Schuckmann,1972).
A worker in a Russian production plant was exposed to chloroformic acidmethyl ester when the skin of his back came into contact with the chemicalduring repair work. The man was wearing a respirator at the time of the ac-cident. Immediately after the accident he only experienced itching andburning of the exposed skin areas. While in the shower, he noticed short-lasting irritation of the eyes and throat (for 3 to 5 minutes) and the urge tocough. Only after a period of 4 to 5 hours during which the man was free ofsigns and symptoms, did he present with dyspnoea, a cough and throa-tache at the plant’s treatment-and-prevention facility, where he was treatedwith calcium chloride and dimedrol (diphenhydramine) and sent home. Af-ter short improvement, his condition deteriorated to the point that he was TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie admitted to hospital 22 hours after the accident occurred. Clinical and x-rayexams revealed pulmonary oedema, which cleared without complicationsafter appropriate treatment (Penknovich and Anikin, 1988).
The concentrations of chloroformic acid methyl ester determined in volun-teers as the odour threshold and the threshold of irritation were 1 mg/m³(equivalent to 0.255 ppm) and 2 mg/m³ (equivalent to 0.51 ppm), respec-tively. A concentration level of 5 mg/m³ (equivalent to 1.3 ppm) was re-ported as severely irritating to the mucous membranes of the eye and tothe respiratory tract in humans (no further details; Gurova et al., 1977).
Classifications and threshold limit values
In the Federal Republic of Germany, the Commission for the Investigationof Health Hazards of Chemical Compounds in the Work Area (“MAK-Kommission”) of the Deutsche Forschungsgemeinschaft has established aMAK value (maximum workplace concentration) for chloroacetic acidmethyl ester on the suggestion of BG Chemie. It was set in the List ofMAK- and BAT Values 2004 at 0,2 ml/m³ (ppm, equivalent to 0,78 mg/m³).
Furthermore, chloroacetic acid methyl ester has been assigned to preg-nancy risk group C, i.e. substances for which “there is no reason to fear arisk of damage to the embryo or foetus when MAK and BAT values are ob-served“ (DFG, 2004; Greim, 2003).
TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie References
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Schädliche Substanzen in der Industrie, Leningrad (1963)Cited in: Gurova et al. (1977) Lide, D.R., Frederikse, H.P.R. (eds.)CRC handbook of chemistry and physics77th ed., p. 3-111CRC Press Inc., Boca Raton, New York, London, Tokyo (1997) TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie LMP (Laboratorium für Mutagenitätsprüfung der Technischen Hochschule Darmstadt)Chloroformic acid methyl ester – induction of gene mutations in mutant strains ofSalmonella typhimurium (Ames test) without and with metabolic activationUnpublished report, LMP 120 (1985)On behalf of BG Chemie LMP (Laboratorium für Mutagenitätsprüfung der Technischen Hochschule Darmstadt)Chloroformic acid methyl ester – chromosome aberrations in cells of Chinese hamstercell line V79Unpublished report, LMP 121 (1986)On behalf of BG Chemie Penknovich, A.A., Anikin, V.V.
Case of acute poisoning by methyl chloroformate (English translation of the Russian)Gig. Tr. Prof. Zabol., No. 10, 57–58 (1988) Plzak, V., Doull, J.
A further survey of compounds for radiation protectionUSAF School of Aerospace Medicine, Aerospace Medical Division (AFSC), Brooks AirForce Base, Texas, USA (1969) Potokar, M., Grundler, O.J., Heusener, A., Jung, R., Mürmann, P., Schöbel, C., Suberg,H., Zechel, H.J.
Studies on the design of animal tests for the corrosiveness of industrial chemicalsFood Chem. Toxicol., 23, 615–617 (1985) RTECS (Registry of Toxic Effects of Chemical Substances)Carbonochloridic acid, methyl ester, RTECS Number FG3675000produced by NIOSH (National Institute for Occupational Safety and Health) (2001) Sax’s dangerous properties of industrial materials9th ed.
Van Nostrand Reinhold Company, New York (1995) Schuckmann, F.
Zur Symptomatik der ChlorameisensäuremethylestervergiftungZentralbl. Arbeitsmed. Arbeitsschutz, 22 (3), 74–76 (1972) Thiess, A.M., Hey, W.
Über eine tödlich verlaufende Chlorameisensäuremethylester-Intoxikation sowie 13weitere Beobachtungen mit Gesundheitsschädigungen nach Einwirkung von Chloramei-sensäuremethylesterZentralbl. Arbeitsmed. Arbeitsschutz, 18, 141–147 (1968) Vernot, E.H., MacEwen, J.D., Haun, C.C., Kinkead, E.R.
Acute toxicity and skin corrosion data for some organic and inorganic compounds andaqueous solutionsToxicol. Appl. Pharmacol., 42, 417–423 (1977) Wardenbach, P.
Written communication to BG Chemie of 07.09.1984 TOXICOLOGICAL EVALUATION No. 36 Chloroformic acid methyl ester 02/2005, BG Chemie

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