In utero exposures

A developing fetus is much smaller than an adult or even young child. The effects of chemical exposure are, therefore, much greater for the fetus. An exposure of lOppb of PCBs wiU have a negligible effect on an adult, but will impair the brain development of a fetus. 

The ferns has an immature, porous blood-brain barrier, allowing greater exposures to the developing brain. 

The fetus has lower levels of some chemical-bonding proteins, allowing a greater accessibility to target organs. 

The developing fetus s organs are rapidly developing and are more vulnerable to toxic attack than fuUy developed organs. 

In the fetus, the systems and organs that detoxify and excrete toxic chemicals are not fuUy developed. This leads to longer residence times and correspondingly greater toxic effects. 

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Environmental exposures to PCBs are significantly lower than those reported in the workplace and are therefore unlikely to cause adverse human health effects in adults. However, it is apparent from the results of several recent studies on children that there was a correlation between in utero exposure to PCBs, eg, cord blood levels, and developmental deficits (65—68) including reduced bkth weight, neonatal behavior anomaUes, and poorer recognition memories. At four years of age, there was stiU a correlation between prenatal PCB exposure levels and short-term memory function (verbal and quantitative). In these studies the children were all exposed to relatively low environmental levels of PCBs. Although these effects may be related to other contaminants, it is clear that this is an area of concern regarding the potential adverse human health impacts of PCBs. 

It is known that the brain is one of the most sensitive sites of action of steroids in utero, and recently there have been suggestions that EDs may affect normal brain development and behaviour. For example, it has been alleged that in utero exposure to polychlorinated biphenyl compounds (PCBs) resulted in adverse effects on neurologic and intellectual function (memory and attention) in young children born to women who had eaten PCB contaminated fish in the USA." It has also been speculated that exposure to environmental pollutants with steroidal activity may be infinencing human sexual development and sexually controlled behavioiir." ... 

Lantz RC, Petrick JS, Hays AM. Altered protein expression following in utero exposure to arsenic. Society of Toxicology, 2005. 

What are the effects on the developing nervous system after chronic in utero exposure Neurophysiological, neurophar-macol ogical, and neuroanatomi cal studies should be useful. 

With the increased use of PCP by young women, pediatricians have begun to identify the newborn s neurobehavioral symptoms after In utero exposure. In 1980, Golden et al. were the first to document the placental transfer of PCP in humans and to describe the resulting neurobehavioral symptoms. They reported on one infant whose mother had smoked an average of six joints per day of marijuana dusted with PCP. The behaviors emerging shortly after birth... 

Children s Susceptibility. Many of the known health effects that have been associated with low level lead exposure have been detected in children who experienced lead exposures both in utero and postnatally. Considerable uncertainty remains about the relative contribution of in utero and postnatal exposures to the development of health outcomes that are expressed later in childhood. This information is important for distinguishing those health outcomes that might be mitigated during the post-natal period from those that must be mitigated by limiting in utero exposure. Considerable uncertainty also remains... 

Silbergeld, EK. 1986. Maternally mediated exposure of the fetus In utero exposure to lead and other toxins. Neurotoxicology 7 557-568. 

Wu K, Xu X, Liu J, Guo Y, Huo X (2011) In utero exposure to polychlorinated biphenyls and reduced neonatal physiological development from Guiyu, China. Ecotoxicol Environ Saf 74 2141-2147... 

In utero exposure to mercury did not produce significant adverse effects on adult performance, although gender differences may interact with methylmercury on certain behaviors... 

Prenatal exposure of mice to the fungicide hexachlorobenzene (HCB) resulted in suppression of the delayed type hypersensitivity (DTH) response to oxazolone. Similar to the DTH response, the in vitro mixed lymphocyte response (MLR) was also suppressed by in utero exposure.101... 

In utero exposure of mice to benzo(a)pyrene (B[a]P) resulted in suppression of the antibody response to SRBC, which persisted for up to 78 weeks in the offspring.102 In a follow up study, injection of B[a]P from gestation day 11 to 17 resulted in suppressed antibody responses to SRBC, MLR and graft versus host responses (GvH). It was suggested that lesions caused by B[a]P in the developing immune system may predispose the host to the growth of neoplasms.103... 

Pregnant mice exposed to benzene from gestation day 12.5 to 19.5 resulted in the reduction of fetal liver pre-B and B cells. Responsiveness to the B cell mitogen LPS was decreased in spleen cell cultures. The results indicate that in utero exposure to benzene alters fetal lymphopoiesis that may be responsible for compromised immune responsiveness postnatally.104... 

Urso, P., and Gengozian, N. Depressed humoral immunity and increased tumor incidence in mice following in utero exposure to benzo[a]pyrene, J. Toxicol. Environ. Health., 6, 569, 1980. 

Gray, L. E., et al. (1997b). In utero exposure to low doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters reproductive development in female Long Evans hooded rat offspring. Toxicology and Applied Pharmacology, 146, 237-244. 

SCHOENIG G P, GOLDENTHAL E I, GEIL R G, FRIT C H, RICHTER W R and carlborg F w, Evaluation of the dose response and in utero exposure to saccharin in the rat, Food Chem Toxicol 1985 23 475-90. 

Rosenstein L, Brica A, Rogers N, et al. 1977. Neurotoxicity of Kepone in perinatal rats following in utero exposure. Toxicol Appl Pharmacol 41 142-143. 

Foster PM (2006) Disruption of reproductive development in male rat offspring following in utero exposure to phthalate esters. Int J Androl 29 140-147... 

Saillenfait AM, Route MB, Ban M, et al Postnatal hepatic and renal consequences of in utero exposure to halothane or its oxidative metabolite trifluoroacetic acid in the rat. J ApplToxicom )-. -%, 1997... 

Wolkowski-Tyl R et ah Evaluation of heart malformations in B6C3F1 mouse fetuses induced by in utero exposure to methyl chloride. Teratology 21 . 91-206, 1983... 

Bogdanffy MS, Tyler TR, Vinegar MB, et al Chronic toxicity and oncogenicity study with vinyl acetate in the rat in utero exposure in drinking water. Fundam Appl Toxicol 23 206-214, 1994... 

The accumulated evidence leaves no doubt that MeHg is a serious developmental toxicant in humans, especially to the nervous system. While the toxicological, and behavioral outcomes resulting from high-concentration in utero MeHg exposures are not in debate, questions regarding risks and mechanisms of action following low-concentration, chronic in utero exposures remain. 

A US National Research Council report states over 60,000 newborns annually might be at risk for adverse neurodevelopmental effects from in utero exposure to MeHg (methyl mercury) . This report clearly makes the point that many infants are exposed to mercury above levels considered safe. 

Smialowicz RJ, Rogers RR, Riddle MM, et al. 1986. Immunological studies in mice following in utero exposure to MCI2. Toxicology 38 293-303. 

The use of opium dates to 4,000 b.c. At that time it was used for medicinal and recreational purposes mainly via inhalation. Today few opium-containing preparations are used, since the activity of opium is largely attributed to its morphine content. The preparations in use today are those that have constipative effects useful for the treatment of diarrhea. Preparations include pantopon, an injectable hydrochloride of opium alkaloids, and paregoric, a camphorated tincture of opium. Paregoric can be used to treat infants with opioid withdrawal signs following in utero exposure to opioids. 

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