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

The Pine River statement: human health consequences of DDT use "Dichlorodiphenyltrichloroethane (DDT) was used worldwide until the 1970s, when concerns about its toxic effects, its environmental persistence, and its concentration in the food supply led to use restrictions and prohibitions. In 2001, more than 100 countries signed the Stockholm Convention on Persistent Organic Pollutants (POPs), committing to eliminate the use of 12 POPs of greatest concern. However, DDT use was allowed for disease vector control. In 2006, the World Health Organization and the U.S. Agency for International Development endorsed indoor DDT spraying to control malaria."

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:

1. remain intact for exceptionally long periods of time (many years)
2. become widely distributed throughout the environment as a result of natural processes involving soil, water and, most notably, air
3. accumulate in the fatty tissue of living organisms including humans, and are found at higher concentrations at higher levels in the food chain
4. 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.

Twelve persistent organic pollutants were initially recognized as causing adverse effects on humans and the ecosystem. These have been placed in 3 categories.

1. Pesticides: aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene;
2. Industrial chemicals: hexachlorobenzene, polychlorinated biphenyls (PCBs); and
3. By-products: hexachlorobenzene; polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF), and PCBs.

Links: Stockholm Convention on Persistent Organic Pollutants | What are POPs?

References

Search Pubmed

Search Pubmed: chemicals in pregnancy

Glossary Links

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Cite this page: Hill, M.A. (2026, February 27) Embryology Abnormal Development - Chemicals. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Abnormal_Development_-_Chemicals

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© Dr Mark Hill 2026, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G