CHEMICAL MIXTURES
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Exposures to multiple solvents or petroleum-chemicals can result in toxic interactions. Even at
low concentrations, mixtures of volatile organic compounds (volatile petroleum derivatives) can
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interact additively or hyperadditively at even subthreshold levels. Respiratory irritation,
headaches, drowsiness of such mixtures show no signs of adaptation,2 and the irritation potential
shows potentiation2 (more than additive effects).
Previous exposure increases the amount of irritation for subsequent exposure,2 which applies
obviously to chronic repeated exposure. Such mixtures cause an inflammatory response in the
respiratory system.2 When the mixtures are more complex and contain more of such chemicals,
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the effects become more hyperadditive and irritant effects can then be seen at levels far below
the threshold limit value.3 Mixtures of such chemicals can also induce intolerance (heightened
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sensitivity) to future low dose chemical exposure. Such intolerance is often associated with a
decline in cognitive functions of learning and memory.5 Repeated low dose exposure over time
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increases the sensitization potential.
Some chemicals dissolve readily in fatty or lipid tissue. Examples of such chemicals include
aromatic hydrocarbons, longer chain aliphatic hydrocarbons and hydrocarbons of larger molecular
weight. These are called "lipophilic"-lipid-seeking. Other chemicals readily dissolve in water or
water-based solutions. Examples are formaldehyde, other aldehydes, many chemical alcohols,
some glycol ethers, organic acids, shorter chain aliphatic hydrocarbons and other smaller
molecular weight chemicals, including inorganics like ammonia, chlorine dioxide, hypochlorites,
etc.
A lipophilic chemical, when in a mixture with hydrophilic chemical(s), penetrates the skin and
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respiratory tract much more easily. Effects of a mixture of hydrophilic and lipophilic chemical
mixture causes adverse effects at far lower levels, affects organs which would otherwise be less
affected, can impair body function at exposures below current legal limits, and can induce reactive
airway disease.7
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Neurotoxicity of Industrial and Commercial Chemicals, Edited by JL O'Donohue, CRC Press, Boca Raton, FL.
HK Hudnell et al., “Exposures of humans to a volatile organic mixture.II. Sensory”, Archiv Env Health 47:31-38,
1992.
A Hempel-Jorgensen et al., “Sensory eye irritation in humans exposed to mixtures of volatile organic compounds”,
Archic Env Health 54: 416-424, 1999.
JE Cometto-Muniz , WS Cain, “Agonistic sensory effects of airborne chemicals in mixtures”, Percept and
Psychophysics 59: 665-674, 1997.
CM Ryan et al., “Cacosmia and neurobehavioral dysfunction associated with occupational exposures to mixtures of
organic solvents”, Amer J Psychiatry 145: 1442-1444, 1988..
HK Hudnell et al., “Time course of odor and irritation effects in humans exposed to a mixture of 22 volatile
organic compounds”, Proceedings of Indoor Air 1993, Vol I. U.S. Environmental Protection Agency.
HI Zeliger, "Toxic effects of chemical mixtures", Archiv Environ Health 58:23-29, 2003.