Even in the "Mad Men" era, when primetime commercials for cigarettes were relentless, many parents urged their children not to smoke — often while chain-smoking in the kids' presence. No one studied (or talked about) the effects of secondhand smoke until the early '90s.
Easy Access to Poison
Child-resistent packaging wasn't legally required until the end of 1970, when President Nixon signed the Poison Prevention Packaging Act. Before that, even toddlers could open containers of everything from prescription drugs to Drano.
The Agent Zero M Sonic Blaster
The James Bond craze of the mid-'60s inspired a wave of toys for junior secret agents, including Mattel's Zero M Sonic Plaster. Held near the ear, this bazooka-like air gun issued a burst of sound so loud it could damage kids' hearing.
Minimal Sun Protection
Back when sunscreen was called "suntan lotion," few parents paid attention to its sun protection factor — before 1972, the SPF didn't even appear on the container. For adults and children alike, the goal was a deep, dark tan, sometimes facilitated by Crisco or Johnson's Baby Oil (SPF: 0).
Optional Seat Belts
The federal law requiring car to be equipped with seat belts took effect in 1968, but that didn't necessarily mean that people wore them. Many didn't bother to buckle their seat belts until states enacted their own laws in the 1980s. Car seats for small children were also optional until around that time.
Gilbert Chemistry Sets
Early Gilbert Chemistry Sets included 56 chemicals, such as ammonium nitrate (a key ingredient in homemade bombs) and the poisonous and flammable potassium permanganate. The Smithsonian's website notes that "Atomic" chemistry sets of the '50s came with radioactive uranium ore. These sets got somewhat safer in the '60s, but weren't really reigned in until the Toxic Substances Control Act of 1976.
Old-school playground were cushioned with asphalt and filled with searing-hot metal. (On the other hand, The New York Times recently reported that today's ultra-safe playgrounds may be stunting children's development.)