Toxic effects of chemical mixtures

In reality, medical scientists cannot yet predict the toxic effects to individual humans from consuming low-level chemical mixtures that permeate our food. Although scientists know virtually nothing about the toxic effects of chemical mixtures, they do know that there can be synergistic effects from multiple chemical exposures.1... 

Toxicologists have only just begun to study the influence of individual synthetic chemicals at low levels on human health. Unfortunately, toxicologists know virtually nothing about the toxic effects of chemical mixtures. Given these unknowns, our exposure to complex mixtures of synthetic chemicals could be responsible for a portion of the background health effects measured in our society. 

Our inability to defend ourselves against new chemicals and mixtures often results in epidemics of disease. For example, asthma, autism, infertility, and many cancers affect different parts of the body and seemingly have different etiologies. All, however, can be related to a combination of genetic predisposition and environmental exposure to chemicals. All are less prevalent where chemical exposures are lower, for example, in rural areas. All have known single chemical exposure causes and they can all be related to low level exposure to chemical mixtures. The toxic effects of chemical mixtures are explored in the chapters that follow. 

Zeliger HI. Toxic effects of chemical mixtures. Arch Environ Health 2003 58(1) 23 29. 

Very little published literature addresses the toxic effects of chemical mixtures in foods. A few have been referred to in the preceding text. Eight other examples follow here. 

In this chapter, examples of the toxic effects of chemical mixtures on workers are presented to demonstrate toxic impacts on those exposed on the job. In order to properly recognize mixture effects, one must have good information on the chemicals to which the individuals are exposed. One must also examine the toxicities of the individual chemicals to ascertain that the impacts on workers are due to mixture effects and not simply those of single chemicals. 

On-the-job exposures offer insight into the toxic effects of chemical mixtures. Though many health effects can be attributed to exposures to single chemicals, others cannot be accounted for by single chemical exposures and are clearly related to exposures to mixtures. This is particularly the case when at least one component of the mixture is a lipophile and at least one other component of the mixture is a hydrophile. The studies referenced in this chapter point out the need to consider mixture exposures when people present with symptoms, rather than dismiss their complaints as being of psychological origin. 

In keeping with the stated purpose of this book, the endocrine disrupting effects of single chemicals are discussed briefly and serve as an introduction to a discussion of the endocrine toxic effects of chemical mixtures. 

Only a very few studies have documented the toxic effects of chemical mixtures on the musculoskeletal system. Almost all of these studies address the effects of tobacco smoking and organic solvent exposure. The following studies are illustrative of those reported. 

Relatively few studies have been carried out on the toxic effects of chemical mixtures on the cardiovascular system. The research that has been published addresses the effects of nonspecific mixtures, including landfill leachates, air pollution, and tobacco smoke. These are discussed in the next three sections. 

The following conclusions can be drawn for the toxic effects of chemical mixtures ... 

The understanding of the toxic effects of chemical mixtures is in its infancy. Our current knowledge has revealed only the proverbial tip of the iceberg. Einstein s quotation at the start of this chapter seemingly applies in the area of toxic effects of chemical mixtures. It is my hope that this book stimulates the research that is needed to expand our knowledge. 

This book really began over thirty years ago, when I was confronted with the first of scores of instances where individuals exposed to chemical mixtures subsequently developed symptoms and effects which could not be explained by the known toxicological effects of the individual chemical species. In some instances, these exposures led to effects far in excess of what would be expected from the exposure. In others, effects were noted following exposures to extremely low levels of chemicals and in still others the body organs targeted were not those known to be impacted by the individual chemicals. Stymied, I advised people to look for other causes of the conditions observed. These inquiries, however, led to my research into the area of toxic effects of chemical mixtures and ultimately to this book. 

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