Introduction

All organ systems (Table 2) can be targets of toxic exposures. Different hazards affect various and differing organ systems [Nelson et al. 2011; Pope AM and Rall DP 1995]. Specific current information about the adverse effects of exposures to chemical and biological agents can be obtained from several publically available resources mentioned in the "What Are Additional Environmental Health Resources?" section.

Respiratory

The respiratory system is both a target organ and a portal of entry for toxicants. Asthma morbidity and death from asthma are increasing. More than 100 toxicants cause asthma, and many more can exacerbate it [Rom 2007].

A large number of xenobiotics and occupations are associated with the development of work-aggravated and work-related asthma. Many high molecular weight xenobiotics, usually plant or animal derived, have been identified, such as

• Arthropod and mite related materials,
• Latex,
• Flour,
• Molds,
• Endotoxins, and
• Biological enzymes.

Lower molecular weight xenobiotics associated with work-related asthma include

• Isocyanates (used in spray paints and foam manufacturing),
• Cleaning agents,
• Anhydrides,
• Amines,
• Dyes, and
• Glues [Nelson et al. 2011].

Skin

Irritant and allergic contact dermatitis account for 90% of occupational skin disorders. Other skin disorders with occupational/environmental exposure etiologies include

• Pigment alterations,
• Chloracne,
• Urticaria, and
• Malignant neoplasms [Levy BS and Wegman DH 2011].

Children appear particularly at risk for toxicity from percutaneous absorption because their skin is more penetrable than an adult's, and specific anatomic sites, such as the face, often represent larger percentage of body surface areas than in the adult [Nelson et al. 2011].

Liver and Kidney

The liver is the primary site of biotransformation and detoxification of xenobiotics. Clinical presentations of toxic liver injury range from indolent, often asymptomatic progression of impairment of hepatic function to rapid development of hepatic failure [Nelson et al. 2011].

The kidneys are exposed to exogenous or endogenous xenobiotics in their role as primary defenders against harmful xenobiotics entering the bloodstream. The environment, the workplace, and, especially, the administration of medications, represent potential sources of nephrotoxicity. Organic solvents and heavy metals are two major classes of toxicants known to adversely affect renal function [Nelson et al. 2011; Pope AM and Rall DP 1995].

Nervous System

Neurotoxicants can cause

• Peripheral neuropathy,
• Ataxia,
• Parkinsonism,
• Seizures,
• Coma, and
• Death.

Many chemicals cause mild central nervous system depression that may be misdiagnosed as inebriation and, if undetected, can progress to psychoses or dementia. Sensory impairment can also be caused by exposure to toxicants (e.g., visual disturbances caused by methanol) and physical agents (e.g., hearing impairment caused by loud noise) [Nelson et al. 2011; Pope AM and Rall DP 1995; Rom 2007].

Reproductive

Toxicants that target the reproductive system can cause a variety of adverse effects. These effects may include

• Early or delayed puberty,
• Early pregnancy loss,
• Fetal death,
• Impaired fetal growth,
• Infertility,
• Low birth weight,
• Menstrual irregularities,
• Premature birth,
• Structural (e.g., cardiac defect) or functional (e.g., learning disability) birth defects, and
• Subfertility.

The impact of exposure to a reproductive toxicant may not be immediately evident. Instead, the effects may emerge at key life transitions. For example:

• When attempting conception,
• During pregnancy,
• During development of the embryo or fetus, in the newborn, and
• During the offspring's childhood, puberty, and eventual fertility as an adult [Association of Reproductive Health Professionals 2010; Sutton et al. 2012].

Cardiovascu-lar and Hematologic

The cardiovascular and hematologic systems are frequent targets of toxicants. Chemical substances may produce adverse effects on the cardiovascular system by acting on the myocardial cells or the autonomic nervous system to affect the:

• Heart rate,
• Blood pressure, or
• Cardiac contractility.

Lead, carbon disulfide, arsenic, cadmium, ozone, and vinyl chloride have all been implicated in the etiology of cardiovascular disease. Benzene can cause bone marrow changes leading to

• Aplastic anemia,
• Acute leukemia, and
• Chronic myelogenous leukemia [Kim et al. 2012; Nelson et al. 2011; Patel et al. 2014; Pope AM and Rall DP 1995; Rom 2007; Zeliger 2013].

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