Just because exposure to certain chemicals don't kill you on the spot doesn't mean they are not harmful to you.
Please at all costs refrain from "Scratch and Sniff" Chemistry.  The nose is a very poor toxic substance indicator, sometimes it only works once.


Chemical Group



Target Organs

Potential Health Effects    

Aromatic Hydrocarbons


Ethyl Benzene

Toluene, Xylene

Commercial solvents

Blood, Bone Marrow, CNS. Eyes Respiratory System, Skin, Liver, Kidneys

All cause central nervous system depression decreased alertness, headaches, sleepiness, loss of consciousness.  Benzene suppresses bone marrow function causing blood changes.  Chronic exposure can cause Leukemia.  Other hydrocarbons can become contaminated with benzene during the distillation process.

Halogenated Aliphatic Hydrocarbons


Tetrachloride, Chloroform, Ethyl Bromide, Ethyl chloride,

Ethylene Dibromide,       Ethylene Dichloride, Methyl Dhooride, 

Methyl Chloroform, Methylene Chloride, Tetrachloroethane, Trtrachloroethylene (Perchlorethylene), Trichlorethylene, Trichlorethane,

Vinyl Chloride

Common solvents

CNS, Kidneys, Liver, Skin

Kidney changes:  Decreased urine flow, swelling (especially around eyes0 anemia. 

Liver changes:  Fatigue, malaise, dark urine, liver enlargement, jaundice.  Vinyl chloride and several others in this group are known carcinogens.

Heavy Metals

Arsenic, Beryllium, Cadmium, Chromium, Lead, Mercury

Wide variety of industrial and commercial uses

Multiple target organs and systems including:  Blood, Cardiopulmonary, Gastrointestinal, Kidneys, Liver, Lungs CNS and Skin

All are toxic to the kidneys.  Each heavy metal has its own characteristic symptom cluster.  For example, lead causes decreased mental ability, weakness, (especially hands). Headaches, abdominal cramps, diarrhea, and anemia.  Lead can also affect the blood forming mechanism, kidneys and the peripheral nervous system.  Long term effects also vary.  Lead toxicity can cause permanent kidney and brain damage; Cadmium can cause kidney or lung disease. Chromium, beryllium, arsenic and cadmium have been implicated as human carcinogens.


Organochlorine Insecticides

Chlorinated ethanes: DDT,

Cyclodienes: Aldrn, Chlordane, Dildrin, Endrin,



Pest Control

Kidneys and Liver, CNS

All cause acute symptoms of apprehension, irritability dizziness, disturbed equilibrium, tremors and convulsions.

Cyclodienes may cause convulsions without any other initial symptoms. 

Chlorocyclohexanes can cause anemia.  Cyclodienes and chlorocyclohexane cause liver toxicity and can cause permanent kidney damage.




Diazinon, Dichlorovos, Dimethoate, Trichlorfon, Malithion, Methyl Parathion, Parathion


Aldicarb, Baygon, Zectran

Pest Control

CNS, Liver, Kidneys

All cause a chain of internal reactions leading to neuro-muscular blockage.  Depending on the extent of the poisoning, acute symptoms range from headaches, fatigue, dizziness, increased salivation and crying, profuse sweating, nausea, vomiting, cramps and diarrhea, to tightness in the chest muscles, twitching and slowing of the heartbeat.  Several may result in rapid onset of unconsciousness and seizures.  A delayed effect may be weakness and numbness in the feet and hands. Long term permanent nerve damage is possible.


Polychlorinated Biphenyl’s (PCBs)


Widely used in industry.  In transformer oils for one

Liver, CHS (Speculatively) Respiratory System (Speculatively) and Skin

Various skin ailments, including chlorachne; may cause liver toxicity.  Possible carcinogen.


After word:  This is not meant to be an all inclusive definitive document on such a complex subject as Toxicology, but rather to draw attention to some of the more common toxic hazards we may become exposed to in our day to day metal workings.  This is also meant to be a living growing document which will be added to and updated from time to time as the need arises or as questions and comments from readers are received. 


The people who read this can generally be categorized into 3 groups: 


            The first are the ones that will read this document and say “Gee, I didn’t know that, I better do something to protect myself.” 


            The second  are the ones that will say “that’s interesting” and continue on as they have in the past. 


            The third  are the ones that will say “I have always done it that way and I ain’t dead yet” and if they have the opportunity, the will challenge me on every point I have tried to make.  To the last group I say please don’t.  I have heard it all before and your argument has no validity.  I operate on the premise that it is ok to be incredibly stupid if you are the only one that knows.  If you argue with me, your secret will be out, and I will tell everybody. 


Addendum To Toxicology:  As Junior Strasil (Irnsrgn) so aptly pointed out, as the chemical changes its’ state of matter from solid to liquid and liquid to gaseous, the hazards associated with the material generally increase.  The changes in the state of matter are usually due to a rise in temperature.  When heated, chemicals can simply vaporize and disperse in the air, they can breakdown into their various components, or they can change into other much more hazardous substances.  For instance, when heated, Freon changes to Phosgene Gas.  This is the same Poison Gas that was used in World War I and is still used as a fumigant in grain elevators.  The same thing happens with Carbon Tetrachloride. 


When two or more chemicals are mixed together reactions can occur that range from merely interesting to toxic to explosive.  Even some common household chemicals when mixed together can produce very hazardous reactions.  Household bleach when mixed with ammonia forms Nitrogen Trichloride Gas.  This gas is deadly if inhaled and extremely explosive if it reaches a source of ignition.  Hydrofluoric Acid, a common ingredient in aluminum brightener, when mixed with any form of an alkali evolves Hydrogen Fluoride Gas which is extremely toxic.  Remember that it is a common practice to use alkalis to neutralize acids and vice versa, but in this case, the result of that reaction is deadly.


Other common chemicals that are found around our shops and garages have the ability to spontaneously combust.  Most of these are in a family called Organic Peroxides.  These are chemicals, usually a flammable solvent that has the peroxide group attached to it. All Organic Peroxides have a Self Accelerating Decomposition Temperature (SADT).  Once they reach this temperature, they decompose.  Some merely off gas vigorously, some ignite and burn quietly and others explode.  These materials have all that is necessary to start a fire built into them.  They have the fuel, a flammable solvent, Oxygen, the Peroxide Group, and when they reach their SADT, they light their own match.  You might think you would have to search far and wide to find something as dangerous at these but that is not the case.  You may have some of them in our shop or garage right now.  Methyl Ethyl Ketone Peroxide (MEKP) always explodes at 140o F. It is the hardener for fiberglass resin.  If you have fiberglass in your garage or shop, you have a small tube of MEKP.  If it reaches 140 degrees it will explode.  That small amount will not blow up your shop or garage, but it may start the fire that will burn it down.  The hardener for body putty, Bondo, is a little more energetic.  Benzyl Peroxide explodes at 90 o F.  It is best to keep this stuff in the refrigerator.  


January 2007 Update:  As was stated in the beginning of this documents, it is the dose that makes the poison.  A tragic example of that was just demonstrated a few days ago when a radio station in California offered a prize for the person that could drink the most water and keep from going to the restroom for the longest time. One of the contestants died from the toxic effects of drinking too much water.