EDIT: I have come across a solution on this post -- How to assign a material to ColladaLoader or OBJLoader. I used the following code which achieved the effect
You can add an environment map to the existing materials of your OBJ model using a pattern like this one:
var loader = new THREE.OBJLoader();
loader.load( 'myModel.obj', function ( object ) {
object.traverse( function ( child ) {
if ( child instanceof THREE.Mesh ) {
child.material.envMap = myEnvironmentMap;
// add any other properties you want here. check the docs.
}
} );
scene.add( object );
} );