Xylenes central nervous system

Solvents acetone, methyl ethyl ketone (MEK), toluene, xylene, glycol, ethers, alcohol defats and dries skin some may be absorbed may carry other components through skin high volatility, exposure possible irritation central nervous system depression (e.g. dizziness, loss of coordination) low to high toxicity, longterm effects... 

Xylene (dimethylbenzene) has been substituted for benzene in many solvent degreasing operations. Like toluene, the three xylenes do not possess the myelotoxic properties of benzene, nor have they been associated with leukemia. Xylene is a central nervous system depressant and a skin irritant. Less refined grades of xylene contain benzene. See Table 56-1 for the TLVs. 

Carpenter et al. (1988) carried out a nested case-control study of cancer of the central nervous system among workers at two nuclear facilities located in Tennessee (United States). They identified 89 cases (72 males and 17 females) who had died between 1943 and 1979. Four controls, living at the time the case was diagnosed, were matched to each case. Job history records were scrutinized by an industrial hygienist to assess potential exposure to each of 26 chemicals or chemical groups. Toluene, xylene (see this volume) and 2-butanone (methyl ethyl ketone) were evaluated as one chemical group the matched relative risk was 2.0 (95% confidence interval (Cl), 0.7-5.5 n = 28) in comparison with unexposed workers. Almost all cases had had low exposure, according to the classification used and there was no dose-response trend. The authors stated that the relative risks w ere adjusted for internal and external exposure to radiation. 

Local irritation and mild central nervous system symptoms were reported in a questionnaire survey, but no abnormalities were seen in a health examination, clinical chemistry, or haematological parameters among 175 xylene-exposed employees, whose exposure to xylene was on average 21 ppm [87 mg/m ] (Uchida et al., 1993). Minor effects on body sway, reaction times or overnight sleep pattern were observed after experimental inhalation exposure to xylene (200 ppm [870 mg/m ], 5 h per day for six days) (Laine et al., 1993). 

Xylene was mentioned as an exposure in four studies. Two were community-based case-control studies, one of which involved brain cancer and one involved several types of cancer. The two industry-based studies were configured as nested case-control studies, one of central nervous system tumours and one of several sites. In none of these studies was xylene the sole or predominant exposure. Cancers at most sites were not significantly associated with xylene exposure in any study. Incidence of colorectal cancer was significantly elevated in the Canadian case-control study, but no other study reported colorectal cancer results. Hodgkin s disease was elevated in one study non-Hodgkin lymphoma was elevated in one study, but not in another. Most results were based on small numbers. In... 

Solvents, such as chlorinated hydrocarbons, toluene, benzene, and xylene, can cause a feeling of euphoria, but they can be deadly toxins. Small, daily doses may cause dizziness, mental confusion, and fatigue high doses will cause permanent damage to the central nervous system. Lead, mercury, and manganese ion poisoning will alter and destroy central and peripheral nerve function and cause personality changes. 

Xylenes and ethylbenzene (Figure 13.7) are common gasoline constituents, industrial solvents, and reagents, so human exposure to these materials is common. The absorption (primarily through inhalation), metabolism, and effects of these solvents are generally similar to those of toluene. Effects are largely on the central nervous system. Effects of xylenes and ethylbenzene on organs other than the central nervous system appear to be limited. 

The aromatic hydrocarbons, such as xylene and toluene, exhibit their toxic effects on the central nervous system. 

SAFETY PROFILE Moderately toxic by ingestion. Mildly toxic by inhalation. A severe skin irritant. Mutation data reported. Avoid excessive contact because of effects of active chlorine on skin. Some of the hydantoins are central nervous system depressants. Mixtures with xylene may explode. Will react with water or steam to produce toxic and corrosive fumes. When heated to decomposition it emits toxic fumes of CT and NO. See also CHLORIDES. 

All the BTEXs cause neurological effects. Neurological effects are the basis for MRLs for both acute and chronic exposures to toluene and mixed xylenes, and for intermediate exposures to benzene neurological effects are not as sensitive for ethylbenzene. The neurological effects consist primarily of central nervous system depression. Toluene s neurotoxicity also includes ototoxicity. Evidence of hearing loss has been seen in both occupationally exposed humans and in animals. There is limited evidence that chronic inhalation exposure to benzene may affect the peripheral nervous system this evidence is from a single study of occupationally exposed humans who also had aplastic anemia. 

Data for the oral route of exposure are less extensive. The BTEXs cause neurological effects, generally central nervous system depression, by the oral route. This is a sensitive effect for toluene and / -xylene, for which it is the basis of acute and/or intermediate MRLs. Renal and hepatic effects are also seen with oral exposure to these compounds. Renal effects are the basis for the intermediate MRL for mixed xylenes and hepatic effects are the basis for the intermediate MRL for m-xylene. The hepatic effects tend to be mild, including increased liver weight and cytochromes P-450 and b5 contents. Benzene causes hematological effects by the oral route that are similar to those seen from inhalation exposure. 

Central nervous system (CNS) depression caused by acute inhalation exposure to volatile aliphatic and aromatic petroleum hydrocarbons is generally thought to occur when the lipophilic parent hydrocarbon dissolves in nerve cell membranes and disrupts the function of membrane proteins by disrupting their lipid environment or by directly altering protein conformation. Oxidative metabolism of CNS-depressing hydrocarbons reduces their lipophilicity and represents a process that counteracts CNS-depression toxicity. More detailed information on this mechanism of toxicity can be found in ATSDR profiles on toluene (ATSDR 1994), ethylbenzene (ATSDR 1999a), and xylene (ATSDR 1995d). 

Other populations are unusually susceptible to the aromatic EC5-EC9 fraction. People with P-thalassemia may be at risk for benzene exposure because some forms of P-thalassemia may exacerbate the adverse effects of benzene on the hematopoietic system. Children and fetuses may be at increased risk to benzene toxicity because their hematopoietic cell populations are expanding and dividing cells are at a greater risk than quiescent cells. Developmental effects in animals are the basis for intermediate inhalation MRLs for ethylbenzene and mixed xylene, indicating that the embryo/fetus may be particularly sensitive to these two BTEXs. People with subclinical and clinical epilepsy are considered at increased risk of seizures from xylene because of its central nervous system effects. 

Exposures to toluene appear to have an initial central nervous system (CNS) stimulatory effect intentional or accidental high exposures are associated with CNS depression (Gamberale and Hultengren 1972 Boor and Hurtig 1977). In humans, accidental exposures to xylene at up to 10,000 ppm resulted in epileptic seizure, complete amnesia, cerebral hemorrhage, unconsciousness, and ventricular fibrillation (Low et al. 1989). There are no relevant studies on low-level chronic exposure to toluene or mixed xylenes in JP-... 

The toxic properties of xylene isomers are similar to toluene or ethylbenzene. The target organs are the central nervous system, eyes, gastrointestinal tract, kidneys, liver, blood, and skin, which, however, are affected only at high levels of exposure. In humans its exposure may cause irritation of the eyes, nose, and throat, headache, dizziness, excitement, drowsiness, nausea, vomiting, abdominal pain, and dermatitis. The irritation effects in humans may be felt at a concentration of 200 ppm in air, while exposure to 10,000 ppm for 6-8 hours may be fatal. 

The oral toxicity of xylene is low. Ingestion of a high dose, however, can cause depression of the central nervous system, dizziness, nausea, and vomiting and abdominal pain. The oral LD50 values in rats for xylene isomers are within the range of 5000 mg/kg. 

A. Toluene and xylene cause generalized central nervous system depression. Like other aromatic hydrocarbons, they may sensitize the myocardium to the arrhythmogenic effects of catecholamines. They are mild mucous membrane irritants affecting the eyes and respiratory and gastrointestinal tracts. 

In the Finnish study of Hohnberg on central nervous system defects in children bom to mothers exposed to organic solvents during pregnancy, 3 of the cases were exposed to toluene, or toluene in combination with other solvents. In one case with hydranencephaly and death 24 days after birth, there was exposure to toluene, xylene, white spirit and methyl ethyl ketone from mbber products manufacture. The second case had multiple abnormali-... 

Central nervous system symptoms of headaches, nausea, dizziness, and drowsiness from acetone, methacrylates, ethyl acetate, ethyl alcohol, methylene chloride, methyl ethyl ketone, toluene, 1,1,2-tricholor-1,2,2-trifluoroethane, and xylene (Quenon 1989) may potentially occur among manicurists. 

BTEX stands for benzene, toluene, ethylbenzene, and xylene, a group of compormds all that also belong to the broader category of Hazardous Air Pollutants (HAPs). Benzene is a known carcinogen, and has also been shown to cause blood disorders and to impact the central nervous system and the reproductive system. Toluene may affect the reproductive and central nervous systems. Ethylbenzene and xylene may have respiratory and neurological effects [1]. BTEX are present in many natural gas streams and are absorbed by the solvent in glycol dehydration and amine sweetening units. 

The vast majority of these SDWA-regulated chemicals were the BTEX compounds—benzene, toluene, xylene, and ethylbenzene. The BTEX compounds appeared in 60 hydraulic fracturing products used between 2005 and 2009 and were used in 11.4 million gal of hydraulic fracfuring fluids. The Department of Healfh and Human Services, the International Agency for Research on Cancer, and fhe USEPA have defermined that benzene is a human carcinogen (ATSDR, 2007). Chronic exposure to toluene, ethylbenzene, or xylene can also damage the central nervous system, liver, and kidneys (USEPA, 2012b). 

Aromatic Hydrocarbons Aromatic hydrocarbons are characterized by one or more six-carbon ring structures with one hydrogen atom per carbon atom. The name aromatic comes from the solvent s aroma. On the whole, aromatic hydrocarbons are local irritants and vasodilators that cause severe pulmonary and vascular injury when absorbed into the body in sufficient concentrations. They can cause dermatitis and can be potent narcotics, with effects on the central nervous system. Of this group, benzene—with its link to leukemia—is strongly regulated and appears to be the most toxic aromatic hydrocarbon. Examples of aromatic hydrocarbons and their respective TLVs are benzene (0.5 ppm), toluene (50 ppm), and xylene (100 ppm). 

Unlike for SFs, the lower the RfD the more potent the chemical. One of the lowest RfDs is for tetraethyl lead, an organic form of lead that can enter the central nervous system and impact intelligence. This form of lead may have led to the mental problems of some of the early Roman emperors (see chapter 1). One of the highest RfDs is for xylenes, a common ingredient of gasoline. RfDs for these two chemicals differ by a factor of about 10, or 100,000. This means that tetraethyl lead is 100,000... 

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