Environmental Pathology 25 Jose´ A. Centeno, Florabel G. Mullick, Kamal G. Ishak{, Teri J. Franks, Allen P. Burke, Michael N. Koss, Daniel P. Perl, Paul B. Tchounwou, and Joseph P. Pestaner Contents 25.1 Introduction. ............................................... 569 25.1 Introduction 25.2 The Skin. ................................................... 570 Humans are constantly exposed to hazardous pollutants in 25.3 The Brain. .................................................. 572 the environment—for example, in the air, water, soil, rocks, 25.4 Inhalation Injury. ......................................... 575 diet, or workplace. Trace metals are important in environ- 25.5 Cardiovascular System. ................................... 580 mental pathology because of the wide range of toxic reactions and their potential adverse effects on the physio- 25.6 Hepatotoxicity of Metal Ions. ............................ 585 logical function of organ systems. Exposures to toxic trace Further Reading. .................................................. 592 metals have been the subject of numerous environmental and geochemical investigations, and many studies have been published on the acute and/or chronic effects of high-level exposures to these types of agents; however, much fewer data are available concerning the health effects of low-dose chronic exposure to many trace metals. Chronic low-dose exposures to toxic elements such as cadmium and arsenic have been shown to cause these metals to accumulate in tissues over time, leading to multiple adverse effects in { exposed individuals. Deceased Exposure to toxic trace metals occurs via three principal J.A. Centeno (*) routes: percutaneous absorption, ingestion, or inhalation. Joint Pathology Center Division of Biophysical Toxicology, The toxic effects may affect specific target organ Malcolm Grow Medical Clinic Joint Base Andrews Air Naval Facility, Washington, DC, USA components, resulting in immunological-induced injury or e-mail: [email protected] specific functional changes. The diseases caused by metals F.G. Mullick T.J. Franks can be genetic or acquired, and the effects can be acute or A.P. Burke chronic. This chapter provides a review of some of these The Joint Pathology Center Silver Spring, MD, USA pathologies and discusses the critical organ systems that are K.G. Ishak{ affected. Examining such toxicities is a medical challenge in that a number of metallic elements, such as iron, copper, and M.N. Koss Medical Laboratories, University of Southern California Medical manganese, are essential to life. Distinguishing normal and Center, Los Angeles, CA, USA pathologic states is critical to our understanding of the path- D.P. Perl ogenesis of metal-induced diseases. The toxic properties of Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA This chapter is dedicated to the memory of Kamal G. Ishak, M.D. Ph.D. P.B. Tchounwou (1928–2004). College of Science, Engineering and Technology, Jackson State The opinions and assertions expressed herein are those of the authors University, Jackson, MS, USA and are not to be construed as official or representing the views of The J.P. Pestaner Joint Pathology Center, the US Department of the Army or the Medical Examiner Office, Washington, DC, USA Department of Defense O. Selinus et al. (eds.), Essentials of Medical Geology: Revised Edition, 569 DOI 10.1007/978-94-007-4375-5_25, # Springer Science+Business Media Dordrecht (outside the USA) 2013 [email protected] 570 J.A. Centeno et al. certain metals, such as lead and mercury, have been acute and chronic health effects in humans. In nature, arsenic acknowledged since ancient times, but enhanced pathologic can occur as metalloid alloys or in a variety of chemical analyses have allowed us to learn much about how metals compounds. In geological media such as rocks, arsenic is can affect specific organ systems. Also reviewed in this commonly found as a sulfide such as orpiment (As2S3)or chapter are the pathologic states caused by metals in the realgar (As2S2) in the form of arseno–pyrite or mixed skin, brain, lung, heart, and liver. sulfides (AsFeS). Significant amounts of arsenic may also be found bound to gold, silver, copper, lead, zinc, and cobalt ores. Mining of these minerals may result in the mobilization 25.2 The Skin and/or transport of arsenic into drinking water. Arsenic has also been used in a variety of agricultural applications (e.g., The list of metals exhibiting dermal toxicity has been well pesticides, insecticides), industrial applications (e.g., catalogued. Such metals include compounds used in medici- manufacturing of solid-state detectors), and medical nal products, industrial processes, pesticides, cosmetics, applications (e.g., drugs and medical treatments). dyes, and jewelry (Lansdown 1995). Of major concern is As with all toxic metals, the toxic effects of arsenic are exposure to metals and metalloids through contaminated related to the chemical and physical forms in which it water and other environmental and geological media. Der- appears: metallic, As(0); inorganic, As(III) and As(V); and mal toxicity is a result of local tissue responses to direct organic, As(III) and As(V). Although arsenic exhibits both contact of a metal with skin or, alternatively, it may repre- organic and inorganic forms, the inorganic trivalent arsenic sent a manifestation of systemic toxicity following ingestion compounds are considered to demonstrate the greatest toxic- or inhalation. Allergic contact dermatitis induced by nickel ity. The molecular basis by which arsenic compounds may is one such example of a local tissue response. The adverse induce their toxicity in humans has been described. cutaneous reactions resulting from chronic ingestion or inha- Impairment of cellular respiration through inhibition of var- lation of arsenical compounds exemplify systemic toxicity. ious mitochondrial enzymes and uncoupling of oxidative A variety of pathologic responses in the skin are phosphorylation is one of the major mechanisms by which associated with both acute and chronic exposures to metals. arsenic exerts its toxic effects. At the molecular level, the Categorization of these responses presents a challenge to the toxicity of arsenic results from its ability to interact with environmental pathologist, as the histologic features sulfhydryl groups of proteins and enzymes and to substitute associated with metal-induced skin lesions may mimic vir- phosphorus in a variety of biochemical reactions (Li and tually any known morphologic skin disease. The more fre- Rossman 1989). In vitro experiments have demonstrated quently encountered morphologic changes include that arsenic reacts with protein sulfhydryl groups to inacti- spongiotic dermatitis (allergic contact dermatitis and pri- vate enzymes such as dihydrolipoyl dehydrogenase and mary irritant dermatitis), granulomatous inflammation, pig- thiolase, thereby producing inhibited oxidation of pyruvate mentation disorders, and cancer. A pertinent exposure and beta-oxidation of fatty acids (Belton et al. 1985). history correlated with pathologic findings should be done Humans are exposed to inorganic arsenic mainly through to establish a precise diagnosis. the oral and inhalation routes. Direct dermal exposure also The occurrence of hyper- and hypopigmentation of the occurs, but to a lesser extent. The oral route includes skin has been reported worldwide in populations chronically contaminated drinking water, food, drugs (including Chi- exposed to arsenic from contaminated drinking water nese herbal medications), and tobacco. Inhalation occurs (see also Chap. 12, this volume). Because of its widespread primarily in occupational settings; workers may be exposed presence in the environment, arsenic has become one of the to arsenic in the air as a by-product of copper and lead most studied elements in environmental toxicology and public smelting, pesticide production, manufacturing of glass, and health. The ensuing discussion centers on arsenic and arsenic- production of semiconductors (Chan and Huff 1997). Arse- related skin diseases, which are considered by many to be the nic tends to concentrate in ectodermal tissues, including the prototype of the development of disease following exposure skin, hair, and nails. Biomethylation is considered the major to a metal. metabolic pathway for inorganic arsenic in humans. Histori- cally, the enzymatic conversion of inorganic arsenic to mono- and dimethylated species has been considered a pri- 25.2.1 Arsenic and Metal-Induced Cancer mary detoxification mechanism of inorganic arsenic; how- of the Skin ever, compelling experimental evidence obtained from several laboratories suggests that biomethylation, particu- The most widely recognized toxic element affecting the skin larly the production of methylated metabolites that contain is arsenic. Arsenic is the twentieth most abundant element in trivalent arsenic, is a process that can activate arsenic as a the Earth’s crust. It is odorless and tasteless and exhibits both toxin and a carcinogen (Styblo et al. 2002; Wei et al. 2002). [email protected] 25 Environmental Pathology 571 Fig. 25.1 Arsenic-induced hyperkeratosis of the hands Fig. 25.1). Arsenical keratoses are characterized by several specific pathologic features, including hyperkeratosis, parakeratosis, and acanthosis (see Fig. 25.2). Nuclear atypia is sometimes present as well. In severe atypia, squamous cells exhibit hyperchromatic nuclei and a disorderly arrangement