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Nano-objects at workplaces
Elżbieta Jankowska
In the article some issues connected with nano-objects (vernacular of the "nanoparticles") and methods of investigation of nano-objects parameters were presented.
Definitions, provisions of law and norms and research projects directed at achieving results associated with real exposure to nano-objects were given.
An also model attempt at the evaluation of potential exposure to nano-objects in a workplace was described.
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3,7-Dimethyl-2,6-octadienal (citral)
Jadwiga A. Szymańska, Barbara Frydrych
3,7-Dimethyl-2,6-octadienal (citral CAS No. 5392-40-5) is a naturally aliphatic aldehyde of the terpene series and is an isomeric mixture of geranial and neral. It is the main component of lemon grass oil, which is found in all citrus fruits and used extensively in the food, cosmetic, and detergent industries. Citral is extracted from lemon grass oil by fractional distillation and also synthesized by oxidation of geraniol, nerol, or linalool. It is a mobile, pale yellow liquid with a strong lemon odor.
In the available literature there are no data on toxicity in humans. Citral is such a common allergenin hand eczema patients due to the combined effects of allergic and irritant properties.
Acute toxicity of citral is low in rodents because the oral or dermal LD50 valkues are over 1000 mg/kg.
Seven bacterial reverse mutation studies indicate negative results with and without metabolic activation. An NTP study shows that there was no evidence of carcinogenic activity in male/female rats and male mice but some evidence of malignant lymphoma in female mice.
Citral is absorbed orally and fairly well absorbed dermally, considering its volatility. Citral is rapidly metabolized and excreted, with urine as the major route of elimination of citral-derived radioactivity.
The value of NOAEL is 217 mg/m3, based on the results of experiments on rats.
Based on these data the authors of this study propose the MAC (TWA) value for citral of 27 mg/m³, MAC (STEL) value of 54 mg/m³ and suggest additional notation: I – irritant substance, A – allergic substance.
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Bis(2-methoxyethyl) ether
Małgorzata Kupczewska–Dobecka
Bis(2-methoxyethyl) ether is a colourless liquid with a slight, pleasant odour.
Diglyme is used mainly as a solvent in water-based paints that are used in the industry (e.g., in spraying cars, metal furniture, household appliances, and machines), as an inert reaction medium in chemical synthesis, in manufacturing integrated circuit boards, primarily as a solvent for photoresists. This substance is included in the European Inventory of Cosmetics Ingredients in the solvent category.
The acute toxicity of diglyme is low after oral exposure or inhalation. Diglyme is slightly irritating to the skin and eyes. No investigations are available on the sensitizing effects of diglyme. The main targets in male animals after repeated intake of diglyme are the reproductive organs. Bis(2-methoxyethyl) ether is a strong teratogen.
Diglyme liquid or vapour is readily absorbed by any route of exposure, metabolized, and excreted mainly in the urine. The main metabolite is 2-methoxyethoxyacetic acid.
Several Ames tests as well as an unscheduled DNA synthesis test did not reveal a genotoxic potential of bis(2-methoxyethyl) ether in vitro. Further, the number of chromosomal aberrations was not increased in bone marrow cells in vivo. The positive results of a dominant lethal test may be due to the effects of diglyme on fertility.
In 2-week inhalation studies in male rats, dose-dependent decreases in weight of testes, epididymides, prostate, and seminal vesicles were observed. The testes were atrophic, and damage of the spermatocytes was observed. The no-observed-adverse-effect level (NOAEL) in these studies was 30 ppm (167 mg/m³); the lowest-observed-adverse-effect level (LOAEL) was 100 ppm (558 mg/m³). On the basis of this experiment MAC value of 10 mg/m³ was proposed. STEL was not established. Notations "Ft" – fetotoxic substance and "Sk" – substance absorbed through the skin were proposed.
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1-Methyl-2-pyrrolidone
Daria Pakulska, Sławomir Czerczak
1-Methyl-2-pyrrolidone is a colorless, hygroscopic liquid with a mild odor of amines. The vapor pressure of the substances is not very high (39 Pa at 20 °C), but due to the wide range of applica-tions, 1-methyl-2-pyrrolidone may exists in vapor and aerosol forms in the workplace, and as a mixture of both. The substance is well absorbed regardless of the route of its administration, as demonstrated in animal and human studies. In studies on volunteers, dermal absorption of 1-methyl-2-pyrrolidone vapors accounted for 30% of the total absorbed dose. Exposure of a rat’s whole body to 1-methyl-2-pyrrolidone at 1000 mg/m³ for 14 days resulted in changes in the inter-nal organs, but exposure through nose to the same concentration resulted merely in nasal irritation. 1-Methyl-2-pyrrolidone has low acute toxicity (LD50, oral: 3914 mg/kg LD50 rabbit, skin: 8000 mg/kg).
Acute inhalation exposure to the compound causes irritation of mucous membranes, functional disorders and depression of the central nervous system in rats. 1-Methyl-2-pyrrolidone did not show genotoxic potential in in vivo and in vitro test systems and did not induce tumors in rats, but acted as a fetotoxic agent. The NOAEL values for the reproduc-tive and developmental toxicity ranged from 206 to 500 mg/m³. Due to the high correlation between the concentration of 1-methyl-2-pyrrolidone in workplace air and the concentration of its metabolite (2-hydroxy-N-methylsuccinimide - 2-HMSI) in urine as well as its slow excretion process, 2-HMSI was considered an appropriate bioindicator of exposure to 1-methyl-2-pyrrolidone. In setting exposure limits, the concentration of 160 mg/m³, which caused a chemosensoric effect in volunteers, is taken into account following the SCOEL expertsʼ approach. This concentration was considered the LOAEL value. It was proposed to reduce the current value of the maximum allow-able concentration (MAC-TWA) of 1-methyl-2-pyrrolidone from 120 to 40 mg/m³. Due to the irri-tating properties of the compound, the MAC-STEL at 80 mg/m³ was proposed. Since the proposed MAC-TWA value (40 mg/m³) is about 5-12 times smaller than the NOAEL values for the reproductive and developmental toxicity, the proposed values of MAC will not only protect workers from exposure to irritation of 1-methyl-2-pyrrolidone and its chemosensoric ef-fects, but also against its harmful effects on offspring. The proposed MAC-TWA and MAC-STEL values are consistent with the values adopted in the European Union, laid down in Directive 2009/161/EU.
The following notations are considered appropriate for 1-methyl-2-pyrrolidone: “Sk” – substance absorbed through the skin, “Ft” – fetus toxic substance and “I” – irritating substance.
In accordance with the Scientific Committee (SCOEL) proposal in the European Union, the value of BEI is recommended (20 mg of 2-HMSI/g in urinary creatinine collected after the morning shift).
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Hydrogen sulfide
Jan Stetkiewicz
Hydrogen sulfide (H2S) is a colorless gas, heavier than air, with the characteristic odor of rotten eggs; it dissolves readily in water to form hydrosulphide water or, at higher concentrations, hydrosulphide acid.
Hydrogen sulfide can be obtained by treating sulfides with acids or, in some cases, with water. Hydrogen sulfide is used in manufacturing sulfuric acid and in the laboratory as a chemical reagent. It is found in some mineral waters, volcanic fumes, and protein decomposition products. According to data released by the Chief Sanitary Inspector, six people were exposed to hydrogen sulfide above the maximum admissible concentration (MAC) (10 mg/m³) in the following Polish NACE (Nomenclature statistique des Activités économiques dans la Communauté Européenne) sectors in 2007: agriculture and hunting, construction, health and welfare services. Hydrogen sulfide is readily absorbed into the body through the lungs and, to a small extent, through the skin. In the organism, it is converted to tiosulfates and sulfates. The process occurs in the enzyme system involving sulfide oxidase, mainly in the liver and kidneys. The process of hydrogen sulfide detoxification that occurs in the intestinal mucosa requires also the involvement of thiol S-methyltransferase. Hydrogen sulfide is partially removed unchanged via the lungs, and with urine as free or conjugated sulfates. The rates of removal of hydrogen sulfide from the body have not been studied (there is no information on the removal rates). On the basis of the speed of recovery of H2S-poisoned people, it has been found that hydrogen sulfide elimination rate (H2S half-life, t1/2) is, roughly, from 60 min to several hours. Hydrogen sulfide toxicity is associated with blocking the activity of enzymes containing metals in the prosthetic group. Hydrogen sulfide in the cells blocks the active iron of cytochrome oxidase, the final enzyme in the mitochondrial respiratory chain, and the activity of carbonyl anhydrase. The tissues that are most sensitive to the activity of hydrogen sulfide include the mucous membranes and the tissues with a high demand for oxygen (nervous tissue and heart muscle). The values of median lethal concentrations of hydrogen sulfide for rats range between 450 and 701 mg/m³ (335–501 ppm). Inhalation exposure of rats and mice to hydrogen sulfide at concentrations of
42–112 mg/m³ for 70–90 days caused damage to the olfactory epithelium and produced signs of bronchial epithelium hyperplasia. Hydrogen sulfide concentration of 14 mg/m3 did not cause damage to the nasal olfactory epithelium or bronchial epithelium in the exposed animals and this value should be assumed to represent NOAEL. No data on the mutagenic, genotoxic or carcinogenic potential of hydrogen sulfide could be located. Hydrogen sulfide does not show embryotoxic or teratogenic activity or reproductive impairment in female rats exposed before and during pregnancy at 4–112 mg/m³. There is also no evidence of the effect of H2S on the growth and development of offspring, or impaired results of the performance or behavioral tests. The major target organs in acute H2S poisoning are the central nervous system and lungs. Hydrogen sulfide at high concentrations (above 4000 mg/m³) causes death of animals within a few to several seconds. It affects the respiratory system, causing cyanosis, dyspnea and eventually death. Exposures to lower concentrations of hydrogen sulfide immediately result in conjunctivitis and painful erosions in the cornea, as well as nose and throat irritation and bronchitis. Frequent complications include bronchopneumonia and pulmonary edema. A considerable number of cases of neurological and neuropsychological changes have been recorded following acute H2S poisoning.
Under conditions of occupational and repeated exposure, the principal target organs of hydrogen sulfide are the nose, eyes and respiratory tract. Odor threshold for hydrogen sulfide is 0.18 mg/m³. Irritation of the conjunctiva and cornea was observed in workers exposed to hydrogen sulfide at 28 mg/m³. Hydrogen sulfide concentration of 14 mg/m³ showed no adverse effect on the respiratory system of volunteers exposed for 30 min, as well as in rats exposed by inhalation for 70–90 days. On the basis of the results of single inhalation exposure of volunteers to hydrogen sulfide, as well as experimental data on chronic inhalation exposure, the concentration of 14 mg/m3 has been adopted for the NOAEL. Assuming the value of only one factor of uncertainty for individual sensitivity is 2, the proposed value of the MAC of hydrogen sulfide should be 7 mg/m³. Considering the irritating and highly toxic activity of hydrogen sulfide, 14 mg/m³ has been proposed as the value of the short-term exposure limit (STEL). The proposed values of the hygienic standards should protect workers from the harmful effects of hydrogen sulfide on the eyes, the airways and the nervous system.
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Carbon tetrachloride
Marek Jakubowski
Carbon tetrachloride (CCl4) is a colorless, volatile and nonflammable liquid with a characteristic odor. In the past, carbon tetrachloride was widely used as a cleaning fluid in industry and dry cleaning establishments and for the production of chlorofluorocarbons used primarily in refrigerants. Because it is nonflammable, it was also used in fire extinguishers. In Poland, concentrations of CCl4 in the air, in industrial settings, were below the present MAC value of 20 mg/m³. The liver, kidney, and central nervous system are the primary targets of toxicity following acute oral exposure to CCl4. Also gastrointestinal irritation has been frequently noted following accidental ingestion of high doses in humans. In the case of chronic inhalation exposure, the liver appears to be the critical organ. Toxic effects of CCl4 in this organ are related to its biotransformation catalyzed by cytochrome P-450 dependent monooxygenase, specifically CYP2E1. Biotransformation of CCl4 yields trichloromethyl radicals and trichloromethylperoxy radicals which can bind to cellular macromolecules such as proteins and lipids. Central nervous system effects include headache, weakness, lethargy, and stupor. Neuro-logical effects are generally observed at exposure levels higher than the threshold for hepatic toxicity.
Carbon tetrachloride has carcinogenic effects in animals. However, the results of investigations suggest that the mechanisms of tumor development are not mainly genotoxic. The carcinogenicity of CCl4 is generally assumed to occur via a non-genotoxic mechanism dependent upon chronic tissue damage.
Occupational exposure limits in different countries range from 3.2 mg/m³ in Germany to 65 mg/m³ in the USA (OSHA) and in Austria. These values are based on the same literature data published between 1950 and 1990.
The MAC (TWA) value for CCl4 was calculated on the basis of NOAEL value of 32 mg/m³ obtained as a result of chronic inhalation exposure of rats. The recommended 8-hour TWA is 6.4 mg/m³. In view of the report of increased serum enzymes in rats treated with 63 mg/m³ carbon tertrachloride for one hour/day, a STEL of 32 mg/m³ was proposed to limit peaks of exposure which could result in hepatotoxicity.
A “skin” notation was recommended as dermal absorption could contribute substantially to the total body burden.
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Tetramethyl succinonitrile
Renata Soćko, Sławomir Czerczak
Tetramethyl succinonitrile (TMSN) is a colorless, odorless solid. TMSN is released when the blowing agent, azo-bisisobutyronitrile, is heated and decomposes during the production of vinyl foam. TMSN is also the by-product of a polymerization catalyst in photocopier toner. In occupational exposure TMSN is absorbed into the respiratory tract in the form of its vapors and into the skin in its liquid or vapor forms. The clinical studies of people exposed to TMSN showed headaches, nausea, convulsions and coma. Animals treated with TMSN developed violent convulsions and asphyxia; death was delayed from 1 minute to 5 hours after the onset of convulsions. The current TLV-TWA of 2.6 mg/m³ for TMSN is based on the subchronic study which was conducted on dogs. The proposed value should protect workers against systemic toxicity manifested in workers as headache, nausea, and convulsions. Additional notation ofTMSN is ‘’Sk’’ – asubstance which can be absorbed through skin.
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