Chemical causation can be clasified as General or Specific . Such distnctions are sometimes critical to the understanding and use of data in the literature. Learn the difference between the two at the linked pages.

Future potential of injury, or risk, usually refers to an exposed population (rather than an individual). Determining this is Risk Assessment. Whereas causation analysis deals with an actual injury that has occurred--and whether or not there is a causal linkage to an exposure-- risk assessment predicts the likelihood of of increased injury to an exposed versus unexposed population. It often relies on mathematical models and extrapolations from animal data to make such predictions. These predictions (risk assessments) are used to regulate chemicals and to compare the relative toxicity of chemicals.

Casarett and Doull's Toxicology, Fifth Ed. , (96)






Prisine arctic, devoid of industry, automobiles and other pollutant sources is showing hotspots of toxic pollutants. Previous studies have shown heavy metals and other contaminants in the arctic ice due to atmospheric transport. Recent studies by Blais et al suggest bioaccumulation of mercury, DDT and other organochorine up the marine food chain and transport to large nesting sites by predator birds. Concentration gradients of the chemicals in the ponds below indicate aa new mode of toxic transport and threats to animal life and to diet of indigenous peoples. Science 309:445

Causation: General versus specific causation--what is the difference, when is each used. Key steps in assessing each.

Indoor Air at home: Where more time is spent than anywhere else, but is the least regulated. Implications for high risk groups: pregnant women, children, the elderly and those with pre existing illnesses. Homes have never been more air tight and built with more synthetic materials. What too look out for. [see also, Toxicology & the Home]

EMF (Electromagnetic frequency) radiation from cell phones and other sources: updated comprehensive review of recent studies, neurological effects, (EHP, 112: 1741-1754).

Terminology and acronyms of Toxicology: What they are, what they mean, how they are used and limitations of usage.

In Depth

The Home




Risk Assessment

Exposure Assessment


Simple Statistics: explanation of basic statistical concepts and tests--l analysis of chemical toxicity; avoiding the traps and confusion.

Pulmonary effects of inhaled ultrafine particles. Mechanisms of toxic action. Three types of particles: coarse (10 um), fine ( < 2.5 um) and ultrafine (< 0.1 um). Although smaller particles have least mass, surface area and concentration in lung tissue highest; cause of pulmonary/cardio vascular effects. [ Int Arch Occup Environ Health(2001) 74(1):1-8; for clinical effects, see Toxicology & Medicine, References ].

Childhood vaccines containing Thimersol, a preservative containing ethylmercury. Significantly higher amounts of mercury in the brain than previously calculated: problems with using methymercury measurments as standard for ethyl mercury. [Environ. Health Persp.113:1015-1021]

On-site Chemical Search

Phthalates: ubiquitous in plastics, cosmetics and other home products. Mechanism of toxicity on hormonal regulation--what this means for exposed populations, especially in utero and in children [for clinical effects see also Toxicology & Medicine, In Depth].

News & Highlights

BELLE: Biological Effects of Low Level Exposure
Hazard Assessment, Analysis
Chemical effects at concentrations orders of magnitude below previously established toxic thresholds. Implications for low level exposure in utero, in children and for at-risk populations.
See also CDC study findings above;
Phthlate and baby boys; PCBs, pesticides and fetal thyroid disruption; Bisphenol A and sugar metabolism [ Toxicology and Medicine,In Depth ].
See also: A challenge to standard toxicity testing?
[Toxicology & Regulation, In Depth ]

World Trade Center Cough:
Hazard Assessment; Exposure Assessment
Chemicals: types, amounts, who exposed?
Latest clinical findings of this persistent condition among exposed emergency workers and the surrounding neighborhood[ Medicine and Toxicology, In Depth]
See also: A unique model to better understand chemically-caused breathing disorders?[ Toxicology & Medicine, Spotlight ]

National Child Study:
Hazard Assessment, Locate

Will examine environmental chemicals and interaction with genetic factors in birth defects, asthma, learning disabilities and other acute and chroinc illnesses in 100, 000 children, ages 0-21, for a number of generations. Coordinated with CDC Report on Human Exposure to Environmental Chemicals [above] and NHANES Survey .
See also, locations of
Child Study Centers.

Toxic Tidbits

In Brief

Toxicology is the study of the adverse effects of chemicals on living systems--people, animals or plants: Did a chemical cause an adverse effect (or exacerbate it) or was the chemical exposure merely coincidental to the injury, with no actual involvement? That is the question that toxicology must address and that this section considers, through real life examples and explanations of the underlying steps and principles that aim to answer this question.

Traumatic injury --such as a broken leg caused by a car accident--is obvious and requires little basic training or methodology to understand its causation. Chemical causation of injury is not so obvious, often 'hidden' from view, and so requires a methodology to distinguish an actual causal link from what appears to be causation but is nothing more than a coincidental juxtaposition of exposure and injury. This often requires going against pre conceived notions and what may at first seem obvious.

Through review and discussion of real life toxic events, this site introduces key concepts, methodologies, and definitions of frequently-used terminology in easy-to-understand language. References to additional articles and links to other source material allow the scientist and layperson alike to research and obtain as detailed and in-depth an understanding as is required. This can then be applied to a range of toxicology issues in medicine, law, regulatory practice and the home.

Hazard Assessment

Book Corner

References & Links

Indoor Air Pollution, Asthma and other Respiratory Problems, see NAS: www.nap.edu/books/0309064961/html/

Endocrine Disruptor Chemicals (EDCs): products commonly found in [see examples, Public Health]

Hurrican katrina: Toxic aftermath and long term toxic consequences. Characterization of the types and amounts of chemicals at area Superfund sites, hazatdous waste dumps, chemical plants. How chemicals are spread by the flood, how they interact with each other and the sediment, and whether they will persist. Key toxics released: how many are among ATSDR's 'Top 20' hazardous substances (of the 275 chemicals that it assesses at Superfund sites, ATSDR identifies 20 most important as community hazards);the risks these chemicals pose to surrounding communities. Airborne risks once the toxic muck begins to dry; persistence in the environment, and bio-accumulation up the marine and land food chain. Read the upcoming review and analysis by Thomas F. Schrager, Ph.D., a toxicologist with twenty years experience working with toxic chemicals in the New Orleans area.


Chemical Toxicity Fact Sheets: summaries of hazard information and regulatory standards from standard-setting agencies world-wide. Differences, similarities; appropriate and inappropriate uses of each. [see also Toxicology & Regulation, In Brief].

General and Specific Causation

Analysis of chemical toxicity is typically divided into three sections:


Epidemiology Primer: power and pitfalls
A look at what epidemiology can tell us about chemical exposure and general causation of chemicals and what it cannot. When is a cause a cause and when is it only an association?


Manganese, Metals and Brain Damage

Hazard Assessment
Federal District Court allows jury to consider link between manganese fume exposure and Parkinsonism. Scientific evidence and how it differs from lead or mercury neurotoxicity.

See Also: Clinical evaluation of toxic effects [Toxicology & Medicine,]
Implications for the Daubert Ruling and as many as 10, 000 law suits nationwide [
Toxicology and Law, News ]


Lead Neurotoxicity: Occurs at blood lead levels much lower than previously thought?

Exposure Assessment, Analysis
Implications for Center for Disease 2010 goal to reduce all child blood lead levels below 10 ug/dl. New research suggests bulk of effect occurs below this threshold. Review latest findings.

See also: Latest results of state of Rhode Island versus paint manufacturers law suit; what it means for RI and across the country [ Toxicology & the Law, Paint Manufacturers ].


ercury, Tuna and Women of Child-bearing Age
Hazard and Exposure Assessment

What the data shows, what it doesn't, what it means and why. Separating fact from rumor, and broad condemnations (on both sides) from a prudent balance between risk and the healthy benefits of fish.



Coming Soon. Review of recent books, including National Academy of Science books on controversial issues of toxicty and chemical exposure. Send us your book to review.


Thomas F. Schrager,Ph.D, Editor

About Cambridge Toxicology Group, Inc.