Lead in soaker hoses
Your concern about lead in your soaker hose is warranted but Lead can be in the brass fittings on your hoses as well. Always check the label on your garden hoses. Sometimes it's hard to find, but it's there. Almost all hoses have a "do not drink" warning, but it's small and you have to look for it. Flush the hose out before you use it. If you can find camper or marine or RV hoses, they are generally safe for drinking. They're made from medical-grade vinyl. Teknor Apex makes Neverkink and Aquaflex R.V. hoses safe for drinking. This is information from the University of Minnesota :
Precautions for garden soils
Studies have shown that lead does not readily accumulate in the fruiting parts of vegetable and fruit crops (e.g., corn, beans, squash, tomatoes, strawberries, apples). Higher concentrations are more likely to be found in leafy vegetables (e.g., lettuce) and on the surface of root crops (e.g., carrots).
To minimize absorption of lead by plants a number of control measures may be taken:
1. Maintain soil pH levels above 6.5. Lead is relatively unavailable to plants when the soil pH is above this level. If needed, add lime according to soil test recommendation. Lead is also less available when soil phosphorus tests are high. For information about obtaining a routine soil test, contact your local Extension office.
2. Add organic matter to your soil. In soils with high lead levels, adding one-third by volume organic matter will significantly reduce lead availability. Organic compounds bind lead and make it less available to the plant. When adding organic matter, the pH should also be maintained above 6.5. Good sources of organic matter include composted leaves, neutral (non-acid) peat, and well-rotted manure. Avoid leaf mulch obtained along highways or city streets as it may contain higher than normal lead levels.
3. Locate your garden as far away from busy streets or highways and older buildings as possible.
4. Because of the possibility of bare soil exposure to children through hand to mouth activity, soils with lead levels exceeding 100 ppm should not be used for gardening. If soil exposure to children is not a concern, then plants can be safely eaten from soils with soil lead levels up to 300 ppm.