There are toxins in just about everything these days that weren't around 100 years ago. Your veges are sprayed with pesticides that run off into the water supply and thus contaminate that. Animals are fed growth hormones and other chemicals to kill bacteria in their systems and this also contaminates their milk, eggs etc and we eat them. Over the counter medications are chemicals that your body does not know how to cope with and thus have a long excretion life in your body. Synthetic materials such as carpets, paints, household cleaners have toxic chemicals that we breathe in. In addition, foods are denatured (trans fats, homogenization, pasteurization, colorants, flavorings etc) and our bodies do not have sufficicient time to eliminate these toxins before the next load / meal / breath of air arrives and so it is relatively easy to get a build up. I could go on and on but that should give you an idea.
1 liter = .91 quarts so they are roughly equal.