Wheel Weights and Water Fleas
Mika Campbell Nishimura
Sir Charles Tupper
Floor Location : M 087 V

I did my project on testing the toxicity of wheel weights in an aquatic environment by observing mortality rates in Daphnia magna. Wheel weights are used to balance the wheels of automotives. Often, wheel weights are thrown from the wheel, get abraded against the road by the passing cars and are then washed down storm drains. This could potentially pollute the lakes and oceans that these storm drains lead to. Currently in Canada, lead wheel weights make up 80% of the market while alternatives include zinc and steel wheel weights. I wanted to see what kind of wheel weight would cause the most mortalities in Daphnia magna, therefore determining the toxicity. My hypothesis was that the lead wheel weight would cause the most mortalities in Daphnia magna because it is a known, toxic, heavy metal and the wheel weight itself had no coating so there was nothing preventing the leaching of toxins and metal ions into the water. To test this, I abraded the wheel weights and placed them into plastic beakers of spring water and let it sit for 24 hours. Then I removed the wheel weight and diluted some of the solution to procure concentrations of 100%, 50%, and 25%. I then placed 5 Daphnia in each beaker for 24 hours. I then recorded the mortalities. My hypothesis was correct, the lead wheel weight had the highest mortality rate in all concentrations in the average of all trials. However, some interesting things I found with the other wheel weights was that zinc, though far more toxic than steel was less toxic that I had expected it to be. This, I believe after further research, was because of the plastic coating could have prevented some the of leaching of toxins into the water. Another surprise was the mortality rate of the steel wheel weight was significantly higher than I expected, because steel itself is a generally non-toxic metal. However, after acquiring more information I discovered steel is actually electroplated with zinc and chromium to stop it from oxidizing. Also, I did not have a method to measure the exact concentration of metal for each of the concentration in all the trials. All in all I hope that this research not only provides the nudge that we need to start going lead free but also gives knowledge to people on a very obscure issue that not very many people are aware of. Maybe now they could make more informed decisions about what goes on their car wheels so that they can help make a difference in preserving the environment.