Lead wouldn't work.
What you need is Hydrogen, and H2O would work fine.
What you need is to reduce the time and/or radiation (from high energy particles). By mining water on the Moon you can do both: reduce the level of radiation and reduce the time get to Mars. Living on the surface of Mars, isn't much of a problem because you can use lots of sheilding. Though traveling around the surface of Mars (for long periods of time (months in total duration) can be a problem, and getting back to Earth quickly is also another problem. [The surface of Mars will have about 1/2 the radiation from high particles as being in space at Mars' distance (in orbit it is also less because Mars would block slightly less than 1/2 the high speed particles).]
Probably best way to lower radiation levels for Mars Manned, would be to use water for sheilding and getting to Mars quickly, then crew establish living quarters and the capability of returning. They stay on Mars for a long time and do little as far as exploring Mars (leave this for follow up crews). The next crew to arrive can learn from first crew and can focus on exploring beyond the camp area. Maybe, the first would leave around same time the third crew lands.