Yes it can be. Latex based paint is used a lot more than oil based in modern times. Check the label to find the identity of the base.
heterogenous
Latex.
you can paint over latex paint with latex enamel.
Oil based metal priming paint along with a 100% acrylic latex exterior house paint.
acrylic
No, the weather will remove it in a year or two.
An average gallon of latex house paint will cover 280 square feet
Can you restate your question are you asking what is the latex paint or are you asking when was the invention of the latex paint.
no. Latex paint is flexible and remains so after curing. Alkyds dry to a solid, non-flexible surface, causing it to usually crack when put over a latex
No, not as far as I have ever heard. Latex paint is harmless unless swallowed.
You can always paint latex ( water based )over an oil based paint as the latex just dries on the surface. However don't paint an oil based over a latex paint. Oil based paints need to absorb into the wood or other surfaces or it will just dry and flake off. For more information on the differences and when or not to use a latex or oil paint please see the following article. . http://www.ehow.com/how_4713170_between-latex-oil-base-paint.html
If you mean latex paint, none. Latex is a water based paint and has no toxic fumes.