识别:
正己烷是一种直链饱和烃,从某些石油馏分经过多种热裂解或催化裂解步骤后获得。商用己烷可能含有20%-85%的
正己烷和各种比例的己烷异构体,包括
2-甲基戊烷、
3-甲基戊烷、2,3-二甲基
丁烯、
环戊烷、
环己烷以及少量的
戊烷和
庚烷异构体、
丙酮、
甲基乙基酮、
二氯甲烷和
三氯乙烯。可能存在微量的苯。
正己烷是一种无色液体,其在
水中的溶解度较低。它能与
酒精、
氯仿和醚混溶。主要用途包括:在鞋厂作为橡胶和粘合剂的溶剂;提取大豆油、蓖麻籽油和亚麻籽油。它还用于制药和化妆品行业,并作为纺织品、家具和皮革产品的清洁剂。
正己烷还用于:测定矿物的折射率、温度计的填充物和变性剂。
人类暴露:目标器官包括:中枢神经系统、周围神经系统、呼吸系统、心脏、皮肤和眼睛。摄入后可能导致
化学性肺炎,并吸入肺部。急性暴露于高浓度
正己烷可能导致中枢神经系统抑制、抽搐、昏迷和死亡。吸入
正己烷通常会引起眼睛、鼻子、喉咙和呼吸道的刺激,停止暴露后这些症状会迅速逆转。如果摄入或吸入与其他可能增强效果的烃类物质相关联,症状会更加严重。外源性
儿茶酚胺可能在敏感的心肌中诱发致命的室性心律失常。急性暴露于高浓度
正己烷可能导致咳嗽、喘息、带血泡沫痰、头痛、眩晕、心动过速和发热。可能引起胃肠道症状。呼吸系统:呼吸缓慢而浅;吸入
正己烷可能导致肺
水肿和
化学性肺炎。心血管系统:心动过速和室性心律失常。中枢神经系统:眩晕、头晕、中枢神经系统抑制综合征。在重度暴露下可能导致昏迷。周围神经系统:慢性暴露可能导致重要的周围神经病(运动感觉)和中枢神经系统异常。胃肠道:恶心、呕吐和厌食。成年人可能在工作场所或自杀尝试时暴露。吸胶
水或
正己烷的嗅吸将个人置于风险之中。儿童可能会意外摄入。使用该溶剂进行提取程序的实验室工作人员、
化学家和药剂师可能会暴露。在工厂,粘合剂和胶
水行业的员工以及印刷和绘画职业的人员。
正己烷通过吸入、摄入或皮肤表面应用而被吸收。在人类志愿者中,大约28%吸入的
正己烷被肺部吸收。肺泡保留量约为吸入剂量的25%,最终吸收率为15%-17%,与总的呼吸道摄取量相关。肥胖个体的肺泡摄取量更大。尽管在体育锻炼期间肺泡摄取率降低,但由于肺通气率提高,
正己烷的总摄取量略有增加。工业工人暴露于商用己烷的
正己烷浓度与血液浓度相关。它通过胃肠道吸收较差。皮肤吸收非常缓慢。吸入或经皮暴露后不到1小时血液中达到峰值。
正己烷对高脂质含量组织的亲和力很大,并且迅速代谢为羟基化合物,然后转化为
2,5-己二酮。最近暴露的工人呼出
正己烷的消除是双相的。快相和慢相的中位半衰期分别为11分钟和99分钟。在没有保护装置的情况下,每天大约暴露7小时的工人尿液中发现了以下代谢物:
2-己醇、
2-甲基-2-戊醇、
3-甲基-2-戊醇、
环己醇、
环己烷和三
氯乙醇。在暴露于高达200 ppm浓度的人类中,稳态血液
水平与剂量相关;即使在1 ppm的暴露下也会发生积累。
动物研究:在细胞色素P-450的氧化代谢的第一步,
正己烷分子的碳1、2、3被羟基化,并在所有动物物种中以不同比例形成
己醇。
正己烷通过肝脏的混合功能氧化酶系统代谢,形成与
葡萄糖醛酸结合的醇或转化为
一氧化碳。
1-己醇和3-
己醛是毒性较低的代谢物。前者被氧化为
己酸,然后经历通常的脂质代谢。在尿液中检测到
2,5-己二酮。短期暴露后,大鼠肺表面活性物质的量和组成发生了重要变化。暴露于不同浓度己烷的大鼠肺部显示出对肺泡细胞的直接毒性作用;脂肪变性,2型肺泡细胞中的肺泡体变化和细胞脱落的增加。在暴露61天后,大鼠的生精小管严重萎缩,免疫反应性生殖
细胞系中神经生长因子的丢失。在暴露后的一些动物中发现了永久的睾丸损伤,生殖
细胞系的总损失持续到暴露后14个月。同时给予
正己烷和
甲苯或二
甲苯并未引起生殖
细胞系的改变或睾丸萎缩。在离体灌注兔心中评估了
正己烷和2,
IDENTIFICATION: n-Hexane is a straight chain saturated hydrocarbon obtained from certain petroleum fractions after various thermal or catalytic cracking steps. Commercial hexane may contain from 20%-85& n-Hexane and various amounts of hexane isomer, 2-methylpentane, 3-methylpentane, 2-3-dimethylbutene, cyclopentane, cyclohexane and small quantities of pentane and heptane isomers, acetone, methyl ethyl ketone, dichloromethane and trichloroethylene. Trace amounts of benzene may be present. N-Hexane is a colorless liquid and solubility in water is low. It is miscible with alcohol, chloroform and ether. Main uses are: rubber and adhesive solvent in shoe factories; extraction of soybean oil, callous seed oil and flaxseed oil. It is used in the pharmaceutical and cosmetic industries and is a cleaning agent for textiles, furniture and leather products. N-Hexane is also used for: determination of the refractive index of minerals, filling for thermometers and denaturant. HUMAN EXPOSURE: The target organs are: central nervous system and peripheral nervous system, respiratory system, heart, skin and eyes. Chemical pneumonia can occur after ingestion and and aspiration to the lungs. CNS depression, convulsions, coma and death may follow acute exposures to large concentrations. Inhalation of n-hexane usually causes eye, nose, throat and respiratory irritation, which are rapidly reversible when exposure is discontinued. Symptoms are more severe is ingestion or inhalation are associated with exposure to other hydrocarbons which may potentiate the effects. Exogenous catecholamines may precipitate a fatal ventricular arrhythmia in the sensitized myocardium. Acute exposure to considerable concentrations of n-hexane may cause cough, wheezing, bloody frothy sputum, headache, dizziness, tachycardia and fever. Gastrointestinal symptoms may result. Respiratory system: slow and shallow respiration; aspiration of n-hexane may cause pulmonary edema and chemical pneumonia. Cardiovascular system: tachycardia and ventricular dysrhythmia. Central nervous system: vertigo, giddiness, CNS depression syndrome. In heavy exposures unconsciousness may result. Peripheral nervous system: chronic exposure may produce important peripheral neuropathy (motor sensory) and CNS abnormalities. Gastrointestinal tract: nausea, vomiting and anorexia. Adults may be exposed in the workplace or in case of suicide attempts. Glue sniffing or n-hexane sniffing puts individuals at risk. There is a potential for accidental ingestion may occur in children. Laboratory workers which use the solvent for extraction procedures, chemists and pharmacists may be exposed. In the factory, glues and adhesives industry employees and those in printing and painting occupations. N-Hexane is absorbed following inhalation, ingestion or by topical application to the skin. In human volunteers about 28% of inhaled n-Hexane was taken up by the lungs. Alveolar retention is about 25% of the inhaled dose of n-hexane and the final absorption is 15%-17% in relation to the total respiratory uptake. Alveolar uptake was greater in obese individuals. Although the alveolar uptake rate decreased during physical exercise, the total uptake of n-hexane increased slightly as a result of the higher lung ventilation rate. Concentrations of n-hexane correlated with blood concentrations in industrial workers exposed to commercial hexane. It is poorly absorbed by the gastrointestinal system. Dermal absorption is very slow. Peak blood levels occur in less than 1 hour following inhalation or percutaneous exposure. N-Hexane has great affinity for high lipid content tissues and is rapidly metabolized to hydroxylated compounds before being converted to 2,5-hexanedione. The respiratory elimination of n-hexane in recently exposed workers was biphasic. The median half-lives of the fast and slow phases were 11minutes and 99 minutes. Workers exposed to n-hexane for about 7 hours/day without protective devices had the following metabolites in the urine: 2-hexanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, cyclohexanol, cyclohexane and trichloroethanol. In humans exposed to concentrations of up to 200 ppm, steady state blood levels were dose dependent; accumulation occurred in humans exposed to as little as 1 ppm. ANIMAL STUDIES: At the first step of oxidative metabolism by cytochrome p-450, the carbons 1,2,3 of n-hexane molecule are hydroxylated and form hexanols in different proportions in all species of animals. N-Hexane is metabolized by mixed function oxidase system in the liver forming alcohols which are conjugated to glucuronic acid or converted to carbon monoxide. 1-Hexanol and 3-hexonal are less toxic metabolites. The former is oxidized to hexanoic acid which undergoes the usual lipid metabolism. 2,5-Hexanedione was detected in urine. In rats exposed to n-hexane, important alterations in the quantity and composition of pulmonary surfactant in rats after short term exposure. The lungs of rats exposed to hexane at different concentrations showed a direct toxic effect on pneumocytes; fatty degeneration, change of alveolar bodies in type 2 pneumocytes and increased detachment of cells. Severe atrophy involving the seminiferous tubules with loss of the nerve growth factor in immunoreactive germ cell line of rats after 61 days of exposure was noted. Permanent testicular damage was found in some animals which had a total loss of the germ cell line lasting up to 14 months after the post exposure period. Simultaneous administration of n-hexane with toluene or xylene did not cause germ cell line alterations or testicular atrophy. In vitro toxicity of n-hexane and 2,5-hexanedione has been evaluated in the isolated perfused rabbit heart. The force of cardiac contraction was significantly reduced following 1 hour of perfusion with n-hexane or 2,5-hexanedione. Spinal neuron cell cultures exposed to n-hexane and butanone developed the neural swelling faster than when exposed to n-hexane. Animal tests have been negative for teratogenic effects. In pregnant rats showed n-hexane blood concentrations in the fetus equal to that found in maternal blood. Isopropanol enhances the induction of n-hexane metabolizing enzymes and increases the 2-hexanol concentrations in the liver and kidney. Methyl isobutyl ketone mixed with n-hexane significantly increased aniline hydroxylase and cytochrome P450 activity in the liver of exposed hens.
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