Laravel Seed - Argument 1 must be array, string given - php

Question

I have the following code in a seeder:
public function develop_run()
{
echo "Running ParentUsersTableSeeder\r\n";
DB::table('parent_users')->truncate();
$faker = Factory::create('en_AU');
$rand = rand(100, 300);
for ($i = 0; $i < $rand; $i++) {
$email = $faker->email;
// Create the new user
$parentUser = ParentUser::create([
'first_name' => $faker->firstName,
'last_name' => $faker->lastName,
'email' => $email,
'country_id' => rand(1, 209),
'last_access_at' => Carbon::today(),
]);
}
}
I cannot understand why the seed fails (at the $parentUser = step) with:
[Symfony\Component\Debug\Exception\FatalThrowableError]
Type error: Argument 1 passed to Illuminate\Database\Grammar::parameterize() must be of the type array, string given, called in /home/vagrant/src/facultyenews/vendor/laravel/framework/src/Illuminate/Database/Query/Grammars/Grammar.php on line 681
The items each individually show correctly if I dd() them. I have other seeds with the same syntax working perfectly, so I assume it is a simple screw up, but I cannot find it.
Any ideas welcome.
Results of dd():
dd($email);
"xlueilwitz#yahoo.com"
dd($faker->firstName);
"Seamus"
dd($faker->firstName);
"Jones"
From another seeder in the same project, this works:
private function createRows($school, $role) {
$faker = Factory::create('en_AU');
$firstName = $faker->firstName;
$lastName = $faker->lastName;
$email = $firstName.'_'.$lastName.'#'.$school->website;
// Preset Users and Schools
$school_user = SchoolUser::create([
'first_name' => $firstName,
'last_name' => $lastName,
'email' => $email,
'password' => bcrypt('a'),
'validated_email' => 1,
'validated_at' => Carbon::now()->subDays(rand(0, 30)),
'last_login_at' => Carbon::now()->subDays(rand(0, 30)),
]);
// Preset Users and Schools
SchoolRoleUser::create([
'school_user_id' => $school_user->id,
'school_id' => $school->id,
'role_id' => $role->id,
]);
}