CHAPTER 9 1 Assess childbearing families for potential exposure to environmental hazards. 2 Discuss elements of the prenatal occupational and environmental history to assess maternal or paternal risk factors. 3 Identify potential risks of environmental hazard exposure to the fetus. 4 Provide support and information to prenatal patients who have had exposure to environmental risks. 5 Identify community resources for health education or referrals relevant to environmental hazards. 6 Educate women of childbearing age regarding potential environmental hazards and how to protect against or minimize exposure. 1. There are more than 29,000,000 commercially available chemicals and more than 240,000 regulated chemical substances in use in the environment today (Chemical Abstracts Service, 2009). 2. More than 84,000 chemical substances are used in the work environment with more than 2000 more added each year. 3. Although the majority of these chemicals are safe and contribute to our daily lives, only a small proportion (<5%) of these chemicals have even been tested for toxic effects on humans (March of Dimes, 2009). 4. Exposure to environmental hazards can occur in the home, at work, or in recreational settings. 5. Environmental hazardous agents are found in the air, water, soil, food, and in household and personal care products. 6. All pregnancies are exposed to potential environmental toxins; physical, biological or chemical substances that are harmful. 7. All pregnancies have a 2% to 4% risk that the fetus will be affected with a major congenital defect (Fisher, Rose, & Carey, 2008). 8. About 5% of congenital defects are caused by exposure to environmental agents (Fisher et al, 2008). 1. Toxic agent: a physical, biological, or chemical substance that is harmful. Toxins can target specific organs or tissues or can have a systemic effect on the entire body (Arble, 2004). 2. Reproductive toxin: a substance or agent that can cause adverse effects on the reproductive system of males or females. The effects of toxic agents may target the reproductive organs, the adrenals, or the thyroid. 3. Fetotoxin: a chemical substance that can poison or cause degenerative effects in a fetus. 4. Teratogen: an agent that acts directly on replicating cells of the developing zygote, embryo, or fetus causing irreversible abnormal development or defects (Arble, 2004). 5. Mutagen: a chemical or physical agent (such as ionizing radiation or hyperthermia) that is genotoxic (capable of inducing changes to deoxyribonucleic acid [DNA]). Germ cell mutagens affect the sperm or ova, causing inheritable effects. If other types of cells are affected, altered cell growth or cell death can result. Harm occurs during early stages of cell division of the zygote. 6. Carcinogen: a substance or condition that increases the incidence of cancer 7. Xenobiotic: a chemical substance, not inherent to the body, which is introduced into the body. Some xenobiotics are beneficial, such as folic acid supplements, but others can be toxic, such as lead. 8. Developmental toxicity: adverse effects observed in the embryo, fetus, or newborn 9. Embryolethality: failure to conceive or spontaneous abortion or stillbirth 10. Embryotoxicity: growth restriction or delayed growth of specific organ systems 11. Endocrine disruptor: a chemical capable of interfering with the proper functioning of estrogen, androgen, and thyroid hormones in humans and animals possibly resulting in alteration in sex ratios or fetal sex development and/or growth 12. Reproductive risk: likelihood that an adverse reproductive outcome will result from a given exposure A Toxicology is the study of how chemical, physical, or biological agents adversely affect living organisms and the ecosystem, and how these effects can be prevented or mitigated. B Dosage: the amount of a chemical administered to an individual measured in mg/kg body weight at one time or over a period of time 1. Dose toxicity is dependent on the chemical’s properties; amount, duration, and timing of dose; route of exposure; absorption; metabolism; excretion; presence of other chemicals (antagonizers or potentiaters); and gender and age (fetus is at increased risk). 1. Acute: a single brief exposure to a substance 2. Subacute: exposure of up to 14 days 3. Subchronic: exposure lasts up to 90 days D Routes of exposure to toxins (exposure may involve more than one route) 1. Inhalation: Toxin is inhaled and passes directly to bloodstream, resulting in increased bioavailability of the agent (Greim & Snyder, 2008). (e) Particulate matter (PM) with aerodynamic diameter <2.5 μm (f) Fumes which may or may not have an odor (2) Associated with intrauterine growth restriction and prematurity (Slama et al, 2008) b. Ingestion: Toxin is taken in orally. Agent undergoes a process of absorption by the intestinal mucosa and is metabolized by the liver (first-pass effect) decreasing the bioavailability of the agent to the systemic circulation (Greim & Snyder, 2008). 2. Dermal contact (absorbed through direct contact with skin) 1. The response to a toxin changes as the dose increases. 2. “The right dose differentiates a poison from a remedy” (Paracelsus) F The target organ for the same chemical can change based on route of entry. 1. Susceptibility varies with the developmental stage at the time of exposure. (1) First 2 weeks after conception (2) Period of rapid cell division and differentiation (3) Mesoderm, endoderm, and ectoderm differentiated (4) Gastrulation and cardiac looping begin. (5) Effects of exposure during this time (1) Organogenesis (3 to 8 weeks after conception) (2) Period of rapid cell growth and differentiation into essential organs (3) Main external features develop. (4) Embryo is most susceptible to damage during this period. (5) Effects of exposure during this time (Polifka & Friedman, 2002) c. Fetal and placental metabolism of substance d. Fetal distribution of substance e. Presence of tissue specific receptors in fetus f. These factors explain the variation of outcomes in pregnancies with similar exposures. C Duration of exposure to agent A Exposure to environmental toxins has reproductive implications for the mother, the father, and the fetus. B Exposure to environmental toxins by either parent prior to conception or by mother or fetus during early development can put the embryo or developing fetus at risk for adverse developmental or genetic outcomes (Silbergeld & Patrick, 2005). C For some toxins, the residual reproductive effects can last for several years after exposure. 3. Altered gestational lengths (preterm or late preterm) 4. Low birthweight or growth restriction a. All pregnancies have a 2% to 4% background risk that the fetus will be born with a major congenital malformation (Fisher et al, 2008). 7. Altered secondary sex ratio (proportion of male births) 8. Conditions that develop later in child’s life 9. Intergenerational effects may continue across future generations if germ cell line affected. 1. Approximately 39 million women of childbearing age between ages 16 and 44 are employed in the civilian workforce accounting for about 46% of the workforce (U.S. Department of Labor, 2008). 2. The workplace has been designed predominantly for men. 3. The National Institute of Occupational Safety and Health (NIOSH, 1999) reports that more than 5000 chemicals have possible reproductive toxicity. 4. Occupational exposures affect the reproductive health of male and female workers. 5. Inaccurate and incomplete exposure data during gestation make determining reproductive risk difficult. 6. Occupational and nonoccupational exposures are difficult to separate. a. Age, lifestyle factors, social class, nutrition, and occupational exposures have been associated with various reproductive outcomes. b. Results of studies to support relationships between occupational exposures and outcomes, specifically birth defects, are not convincing (Thulstrup & Bonde, 2006) B Common occupationally related environmental hazards a. Antineoplastic drugs (Connor & McDiarmid, 2006) (a) Drugs used for treatment for cancer (b) Combination therapy of antineoplastic drugs more common (c) Antineoplastic drugs are also used to treat conditions other than cancer. (a) Health care workers and pharmacists are at increased risk. [i] Prepare and handle antineoplastic drugs [ii] Handle contaminated excreta of patients taking antineoplastic drugs while providing care [iii] Unsafe handling of antineoplastic drugs (3) Classes of antineoplastic drugs (a) Alkylating agents: nitrogen mustard, nitrosoureas (c) Mitotic spindle inhibitors (d) Epipodophylotoxins: teniposide and etoposide (e) Antitumor antibiotics: bleomycin, daunorubicin, doxorubicin (g) Miscellaneous drugs: L-asparaginase (h) All classes of antineoplastic drugs are mutagenic and carcinogenic. (a) Inhalation of droplets or particles during preparation (b) Dermal exposure during preparation or cleanup c. Ethylene oxide (Center for the Evaluation of Risks to Human Reproduction [CERHR], 2002) (a) Production of ethylene glycol for antifreeze, polyester fibers and films, and detergents (b) Sterilization of equipment and supplies in health care facilities (c) Fumigant in the manufacture of medical products and foodstuffs (a) Engineered particles of extremely small size (1 to 1000 nanometers) with unique optical, chemical and magnetic properties that differ from their related chemical compound (b) Used in suntan lotion, cosmetics, clothing, cleaning materials, medicines, and food (c) Emerging applications for nanoparticles are under development. (a) Nanotechnology research and development workers (b) Chemical and pharmaceutical workers (c) Workers who handle powders related to paint, pigments, and concrete (a) Nanoparticles are small enough to penetrate the body at the molecular level. (b) They bypass the body’s usual defense mechanisms. (c) Reproductive effects are unknown. [i] Nanoparticles cross the blood-testes barrier. [ii] Deposit in testes and have potential for adverse effects on sperm (McAuliffe & Perry, 2007) [iii] More research is needed to determine safety and reproductive effects of this emerging technology (U.S. Department of Health and Human Services [USDHHS], 2009). (a) Chemicals with high volatility and high vapor pressure that are lipid soluble, used to dissolve oil, resins, and rubber [i] Aliphatic hydrocarbons (mineral spirits, varnish, kerosene) [ii] Aromatic hydrocarbons (benzene, toluene, xylene) [iii] Halogenated/chlorinated hydrocarbons (carbon tetrachloride, trichloroethylene, tetrachloroethylene [also known as perchloroethylene, or perc]) [iv] Aliphatic alcohols (methanol) (a) Spot removers, aerosol sprays, paints (d) Furniture stripping, glues (f) Nail polish and polish remover (a) Workers in manufacturing and industry jobs (e) Medical laboratories workers (g) Abusers of solvents such as paint sniffers (a) Women exposed to organic solvents in work or hobbies have an increased risk for infants born with gastroschisis (Torfs, Katz, Bateson, Lam, & Curry, 1996). (b) Increased risk for intrauterine growth restriction (IUGR) and small-for-gestational-age (SGA) infant (Ahmed & Jaakkola, 2007) (d) Neurodevelopmental toxicity (Laslo-Baker et al, 2004) (f) Congenital solvent exposure syndrome may exist (Bowling, Gaudette, & Pergament, 2006). g. Phthalates (Gray, 2000; Khattak et al, 1999) (a) Chemicals used to soften plastic (b) Found in many personal care products and medical supplies (c) Plastic products including water bottles, food wrap (d) Found in polymers coating some medications (Hernández-Diáz, Mitchell, Kelley, Calafat, & Hauser, 2009) h. Polychlorinated biphenyls (PCBs) (a) A group of 290 synthetic organic compounds (b) Used to manufacture dielectric capacitors and transformers (c) Found in heat-exchange fluid and hydraulic fluid (d) Production of PCBs in the United States was banned in 1977. (a) Capacitor manufacturing workers (b) Women who consume moderate to high amounts of contaminated fish (a) Preterm delivery and induced abortion (Tsukimori et al, 2008) (d) Low intelligence quotient (IQ) scores in the child (e) Possibly at least 2-year lag in reading comprehension (g) Exposure during fetal development poses increased risk for health effects.
Environmental Hazards
INTRODUCTION
OVERVIEW OF PRINCIPLES OF TOXICOLOGY
OVERVIEW OF PRINCIPLES OF TERATOLOGY
Reproductive Risks of Environmental Toxins
Environmental Hazards in the Workplace
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