Why so many dangerous products are for sale

Given that the U.S. Consumer Product Safety Commission examines only a tiny portion of the thousands of products it regulates, plenty of unsafe toys, appliances and clothing manage to find their way onto America's store shelves.

Discounter Dollar Tree (DLTR) is the top offender among retailers cited in CPSC inspections, according to a report Tuesday by Bloomberg.

Dollar Tree is currently under investigation by the CPSC, according to regulatory filings cited by the news service, over "product safety incidents reported since 2009." The retailers Target (TGT) and Zulily (ZU) are next in line behind Dollar Tree in numbers of safety violations discovered in CPSC inspections over the past couple of years, the report said.

Dollar Tree, Target and Zulily all told Bloomberg they test the products that they import and take safety seriously.

Among the violations Dollar Tree was cited for include having children's products with excessive levels of lead (lead is virtually banned from such products) and excessive phthalates (chemicals that soften plastics and make them more flexible), and for importing products made for young children that had parts too small to be safe.

When it comes to product safety, the system overwhelmingly relies on companies to police their suppliers and then turn themselves in if they've been selling a product that turns out to be dangerous. Periodically, companies are penalized by the safety agency after being accused of ignoring reports from consumers who reported defects, incidents or injuries.

The CPSC maintains a public database of safety complaints consumers lodge on its SaferProducts.gov website. Consumers direct far more complaints to the companies, but the government site gives consumers a window into issues others have experienced regardless of whether the product has reached the point of a recall. Recall notices are also included in the database.

Consumers filed 41 reports about products purchased at Dollar Tree since the CPSC began publishing the reports in 2011.