[1] He graduated from Brooklyn College in 1954, and earned his master's degree from New York University Stern School of Business in 1956,[2] where he later was on the board of overseers.

As an outside board member, Rennert was not dragged down by the collapse and began to raise junk bonds on his own behalf to finance acquisitions for the Renco Group.

[citation needed] Rennert's strategy for building Renco was to acquire all the shares of struggling companies and to finance the acquisition by issuing junk bonds.

[citation needed] In 1997, Doe Run went on to pay $247 million for a similarly environmentally troubled lead smelting complex from the Peruvian government, as well as borrowing more money to service its Fluor Corporation debt.

[7] Despite losing the company, Renco agreed to assume responsibility for the existing pension plan, with ongoing support from WCI.

The initial lawsuit DOJ filed on behalf of EPA in 2001 claimed U.S. Magnesium was not following regulations promulgated under the Resource Conservation and Recovery Act of 1976, which dictates how waste byproducts must be disposed.

The EPA published its proposal to place the US Magnesium facility on the National Priorities List (NPL, a "Superfund site" under CERCLA) in the Federal Register on September 3, 2008.

On January 14, 2011, the United States Court of Appeals sided with the EPA and upheld placing the site on the National Priority List.

In 1998, the EPA placed Renco Group business holdings 10th on the nation's largest polluter list primarily because of emissions from US Magnesium in Utah (formerly MagCorp).

They demanded nearly $1 billion in fines, alleging MagCorp (a Renco Metals Inc. subsidiary) dumped toxic waste in ditches and ponds on the Great Salt Lake.

[16] The suit claimed PCB-laced sludge and dust choked the plant's plumbing, wastewater ponds, landfill and ditches, where contaminants were 12 times the allowed limit for accidental release.

[16] MagCorp maintained it was exempt from the federal Resource Conservation and Recovery Act, which requires companies to monitor certain kinds of hazardous waste.

[16] Magcorp declared Chapter 11 bankruptcy shortly after the lawsuit began and a federal judge allowed Rennert to restructure MagCorp—now U.S. Magnesium—which exempted it from previous legal liability.

[19] The energy improvements in US Magnesium's manufacturing process have also caused a net reduction of 100,000 tons per year of carbon dioxide emissions.

EPA and MDNR continue to work with Doe Run to address stabilization, erosion control, flood protection, stormwater collection and treatment, and wetland mitigation related to the slag pile area at the site.

EPA and MDNR are also working with Doe Run to address soil recontamination of residences near the smelter and contamination along city haul routes.

"[citation needed] In the first quarter of 2007, Doe Run met all of the National Ambient Air Quality Standards (NAAQS).

[citation needed] By 2008, the conditional approval proposed, which covered air dispersion model selection as well as meteorological and emissions inventory data, among others, for the operation of the smelter was incorporated to the 2007 Consent Judgment between the company and the state of Missouri.

The smelter was sold to Doe Run in 1997 primarily because the Peruvian government passed a law that required environmental improvement at the business.

[28] A study by St. Louis University scientists found that 97 percent of children in La Oroya suffer from mental and physical deficiencies related to their exposure to polluted air.

They also gave over $1 million to the World Trade Center Memorial and established the Rennert Entrepreneurial Institute of Sy Syms School of Business at Yeshiva University.

The Rennerts are known to have donated to Rabbi Aharon Bina's new yeshiva in Israel, Yeshivat Netiv Aryeh, and are additionally honored with a plaque as well as their family upon entrance into the building.

[42] Rennert caused controversy among his neighbors by building a beach front home in Sagaponack, New York, considered one of the largest occupied residential compounds in the United States.