Abnormal Development - Chemicals
Introduction
Effects due to environmental chemicals on development, both pre- and post-natal are difficult to quantify. There are also chemical hazards to development covered elsewhere in these notes, Metals, Fetal Alcohol Syndrome, smoking, illicit drugs.
The specific effects of chemicals is detailed in chemical Material Safety and Data Sheets (MSDS) available from an chemical index page that relate to developmental abnormalities. These sheets are now generally required to be supplied along with the chemical purchased from a supplier and give a standardised description of the chemical, its physical properties, handling and health effects/toxicity.
There are also several WWW sites that have searchable databases of MSDS information. Note that handling chemical saftey may vary from country to country.
Some Recent Findings
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Chemical Terms
Below are listed some terms which relate to a chemicals harmful effects.
Carcinogen
A chemical known or believed to cause cancer in humans. The number of known carcinogens is comparatively small, but many more chemicals are suspected to be carcinogenic.
Effective Dose
(ED50) The amount of material required to produce a specified effect in 50% of an animal population. (See qualification in the definition of LD50).
Lethal Dose
(LD50) The dose of a chemical which kills 50% of a sample population. In full reporting, the dose, treatment and observation period should be given. Further, LD50 and ED50 values are strictly only comparable when the age, sex and nutritional state of the animals is specified. Nevertheless, LD50 values are widely reported as a measure of the potential toxicity of chemicals.
Mutagen
An agent that changes the hereditary genetic material which is a part of every living cell. Such a mutation is probably an early step in the sequence of events that ultimately leads to the development of cancer.
Threshold Limit Value
(TLV) The maximum permissible concentration of a material, generally expressed in parts per million in air for some defined period of time (often 8 hours). These values, which may differ from country to country, are often backed up by regulation and are therefore often legally enforceable.
Persistent Organic Pollutants
(POPs) These are organic (carbon-based) chemical substances with a combination of physical and chemical properties that once released into the environment:
- remain intact for exceptionally long periods of time (many years)
- become widely distributed throughout the environment as a result of natural processes involving soil, water and, most notably, air
- accumulate in the fatty tissue of living organisms including humans, and are found at higher concentrations at higher levels in the food chain
- are toxic to both humans and wildlife
Stockholm Convention on Persistent Organic Pollutants
The Stockholm Convention on Persistent Organic Pollutants is a global treaty to protect human health and the environment from chemicals that remain intact in the environment for long periods, become widely distributed geographically, accumulate in the fatty tissue of humans and wildlife, and have adverse effects to human health or to the environment. The text of the Stockholm Convention on Persistent Organic Pollutants was adopted 22 May 2001 and entered into force ninety days after the deposit of the fiftieth instrument of ratification, acceptance, approval or accession by a country to the Convention, 17 May 2004.
Twelve persistent organic pollutants were initially recognized as causing adverse effects on humans and the ecosystem. These have been placed in 3 categories.
- Pesticides: aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene;
- Industrial chemicals: hexachlorobenzene, polychlorinated biphenyls (PCBs); and
- By-products: hexachlorobenzene; polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF), and PCBs.
Annex A (Elimination)
Parties must take measures to eliminate the production and use of the chemicals listed under Annex A. Specific exemptions for use or production are listed in the Annex and apply only to Parties that register for them.
Aldrin, Chlordane, Chlordecone, Dieldrin, Endrin, Heptachlor, Hexabromobiphenyl, Hexabromodiphenyl ether and heptabromodiphenyl ether, Hexachlorobenzene (HCB), Alpha hexachlorocyclohexane, Beta hexachlorocyclohexane, Lindane, Mirex, Pentachlorobenzene, Polychlorinated biphenyls (PCB), Tetrabromodiphenyl ether and pentabromodiphenyl ether, Toxaphene
Annex B (Restriction)
Parties must take measures to restrict the production and use of the chemicals listed under Annex B in light of any applicable acceptable purposes and/or specific exemptions listed in the Annex.
DDT, Perfluorooctane sulfonic acid, its salts and perfluorooctane sulfonyl fluoride
Annex C (Unintentional production)
Parties must take measures to reduce the unintentional releases of chemicals listed under Annex C with the goal of continuing minimization and, where feasible, ultimate elimination.
Polychlorinated dibenzo-p-dioxins (PCDD), Polychlorinated dibenzofurans (PCDF), Hexachlorobenzene (HCB), Pentachlorobenzene, Polychlorinated biphenyls (PCB)
Polychlorinated Biphenyls
An example of the effects of polychlorinated biphenyls (PCBs) can be seen following contaminated rice oil consumption in Taiwan between 1978-1979.[2][3]
- "Yucheng "oil-disease" victims were Taiwanese people exposed to polychlorinated biphenyls (PCBs) and their heat-degradation products, mainly polychlorinated dibenzofurans (PCDFs), from the ingestion of contaminated rice oil in 1978-1979. Serial studies in Yucheng offspring born between 1978 and 1992 are summarized. Children of the exposed women were born with retarded growth, with dysmorphic physical findings, and, during development, with delayed cognitive development, increased otitis media, and more behavioral problems than unexposed children. Recently, examination of the reproductive system has suggested that prenatal exposure exerts late effects on semen parameters in young men after puberty. Results of the investigation in Yucheng children will provide important information about the human health effects and toxicology of PCB/PCDF exposure. Prenatal exposure to these environmental chemicals causes the fetus to be sensitive to the toxic effects of persistent organic pollutants." [2]
Endosulfan
Endosulfan is commercial name for a chemical (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro- 6,9-methano-2,4,3-benzodioxathiepin-3-oxide) broad-spectrum insecticide and acaricide to control agricultural insect and mite pests in crops. Technical-grade endosulfan is composed of two stereochemical isomers, alpha-endosulfan (70%) and beta-endosulfan (30%), at high levels chemical has acute toxicity and neurological effects.
An Indian study has suggested that it acts as an endocrine disruptor, exposure in male children may delay sexual maturity and interfere with sex hormone synthesis.[4] There has been some criticism of the data used in this particular study.[5][6]
USA - National Toxicology Program
The following information is an excerpt from the website background information (February 17, 2005).
- The NTP is an interagency program whose mission is to evaluate agents of public health concern by developing and applying tools of modern toxicology and molecular biology. The program maintains an objective, science-based approach in dealing with critical issues in toxicology and is committed to using the best science available to prioritize, design, conduct, and interpret its studies. To that end, the NTP is continually evolving to remain at the cutting edge of scientific research and to develop and apply new technologies.
- More than 80,000 chemicals are registered for use in the United States. Each year, an estimated 2,000 new ones are introduced for use in such everyday items as foods, personal care products, prescription drugs, household cleaners, and lawn care products. We do not know the effects of many of these chemicals on our health, yet we may be exposed to them while manufacturing, distributing, using, and disposing of them or when they become pollutants in our air, water, or soil. Relatively few chemicals are thought to pose a significant risk to human health. However, safeguarding public health depends on identifying both what the effects of these chemicals are and at what levels of exposure they may become hazardous to humans—that is, understanding their toxicology.
Center for the Evaluation of Risks to Human Reproduction
The National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR) was established in 1998 to serve as an environmental health resource to the public and regulatory and health agencies. CERHR publishes monographs that assess the evidence that environmental chemicals, physical substances, or mixtures (collectively referred to as "substances") cause adverse effects on reproduction and development and provide opinion on whether these substances are hazardous for humans.
Australia - National Measurement Institute
National Measurement Institute (NMI) is Australia's peak measurement body responsible for biological, chemical, legal, physical and trade measurement.
National Research Centre for Environmental Toxicology (Queensland)
(EnTox) Entox is a Joint Venture of the University of Queensland and the Queensland Department of Health.
References
Reviews
<pubmed>18470797</pubmed>| J Toxicol Environ Health B Crit Rev.
Articles
<pubmed>19683226</pubmed>
Search Pubmed
Search Pubmed: chemicals in pregnancy | Persistent Organic Pollutants
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Cite this page: Hill, M.A. (2026, February 26) Embryology Abnormal Development - Chemicals. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Abnormal_Development_-_Chemicals
- © Dr Mark Hill 2026, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
