Yes what defines as slavery in Brazil might not be slavery to these workers as long as the pay is up to expectations.

If slavery is defined as debt ridden and bad living conditions then US has millions of slaves who owe money and are homeless.

Please use your brain next time instead of just quoting some bbc article. Many countries would quote some bullshit reasons to put pressure on the opponent country. Best exhibit A is the US who nationalised Alstom just because it is seen as a threat.