diff --git a/mk/rt.mk b/mk/rt.mk
index 72578bcdb40..6d5fb862cf5 100644
--- a/mk/rt.mk
+++ b/mk/rt.mk
@@ -10,6 +10,7 @@ RUNTIME_CS := rt/sync/timer.cpp \
               rt/rust_run_program.cpp \
               rt/rust_crate_cache.cpp \
               rt/rust_comm.cpp \
+              rt/rust_env.cpp \
               rt/rust_scheduler.cpp \
               rt/rust_task.cpp \
               rt/rust_task_list.cpp \
@@ -38,6 +39,7 @@ RUNTIME_HDR := rt/globals.h \
                rt/rust_internal.h \
                rt/rust_util.h \
                rt/rust_chan.h \
+               rt/rust_env.h \
                rt/rust_port.h \
                rt/rust_scheduler.h \
                rt/rust_task.h \
diff --git a/src/rt/memory_region.cpp b/src/rt/memory_region.cpp
index 44924218e57..7114aa5b324 100644
--- a/src/rt/memory_region.cpp
+++ b/src/rt/memory_region.cpp
@@ -14,7 +14,7 @@ memory_region::alloc_header *memory_region::get_header(void *mem) {
 
 memory_region::memory_region(rust_srv *srv, bool synchronized) :
     _srv(srv), _parent(NULL), _live_allocations(0),
-    _detailed_leaks(getenv("RUST_DETAILED_LEAKS") != NULL),
+    _detailed_leaks(srv->env->detailed_leaks),
     _synchronized(synchronized), _hack_allow_leaks(false) {
 }
 
diff --git a/src/rt/rust.cpp b/src/rt/rust.cpp
index df1486952eb..0d25d2c3248 100644
--- a/src/rt/rust.cpp
+++ b/src/rt/rust.cpp
@@ -76,56 +76,6 @@ command_line_args : public kernel_owned<command_line_args>
 };
 
 
-#if defined(__WIN32__)
-int get_num_cpus() {
-    SYSTEM_INFO sysinfo;
-    GetSystemInfo(&sysinfo);
-
-    return (int) sysinfo.dwNumberOfProcessors;
-}
-#elif defined(__BSD__)
-int get_num_cpus() {
-    /* swiped from http://stackoverflow.com/questions/150355/
-       programmatically-find-the-number-of-cores-on-a-machine */
-
-    unsigned int numCPU;
-    int mib[4];
-    size_t len = sizeof(numCPU);
-
-    /* set the mib for hw.ncpu */
-    mib[0] = CTL_HW;
-    mib[1] = HW_AVAILCPU;  // alternatively, try HW_NCPU;
-
-    /* get the number of CPUs from the system */
-    sysctl(mib, 2, &numCPU, &len, NULL, 0);
-
-    if( numCPU < 1 ) {
-        mib[1] = HW_NCPU;
-        sysctl( mib, 2, &numCPU, &len, NULL, 0 );
-
-        if( numCPU < 1 ) {
-            numCPU = 1;
-        }
-    }
-    return numCPU;
-}
-#elif defined(__GNUC__)
-int get_num_cpus() {
-    return sysconf(_SC_NPROCESSORS_ONLN);
-}
-#endif
-
-int get_num_threads()
-{
-    char *env = getenv("RUST_THREADS");
-    if(env) {
-        int num = atoi(env);
-        if(num > 0)
-            return num;
-    }
-    return get_num_cpus();
-}
-
 /**
  * Main entry point into the Rust runtime. Here we create a Rust service,
  * initialize the kernel, create the root domain and run it.
@@ -133,17 +83,16 @@ int get_num_threads()
 
 int check_claims = 0;
 
-void enable_claims(void* ck) { check_claims = (ck != 0); }
-
 extern "C" CDECL int
 rust_start(uintptr_t main_fn, int argc, char **argv, void* crate_map) {
 
-    update_log_settings(crate_map, getenv("RUST_LOG"));
-    enable_claims(getenv("CHECK_CLAIMS"));
-    int num_threads = get_num_threads();
+    rust_env *env = load_env();
 
-    rust_srv *srv = new rust_srv();
-    rust_kernel *kernel = new rust_kernel(srv, num_threads);
+    update_log_settings(crate_map, env->logspec);
+    check_claims = env->check_claims;
+
+    rust_srv *srv = new rust_srv(env);
+    rust_kernel *kernel = new rust_kernel(srv, env->num_sched_threads);
     kernel->start();
     rust_task *root_task = kernel->create_task(NULL, "main");
     rust_scheduler *sched = root_task->sched;
@@ -159,13 +108,13 @@ rust_start(uintptr_t main_fn, int argc, char **argv, void* crate_map) {
 
     root_task->start(main_fn, (uintptr_t)args->args);
 
-    DLOG(sched, dom, "Using %d worker threads.", num_threads);
-
     int ret = kernel->start_task_threads();
     delete args;
     delete kernel;
     delete srv;
 
+    free_env(env);
+
 #if !defined(__WIN32__)
     // Don't take down the process if the main thread exits without an
     // error.
diff --git a/src/rt/rust_builtin.cpp b/src/rt/rust_builtin.cpp
index 4870c9fe545..6f45227bb8b 100644
--- a/src/rt/rust_builtin.cpp
+++ b/src/rt/rust_builtin.cpp
@@ -857,10 +857,10 @@ clone_chan(rust_task *task, rust_chan *chan) {
 }
 
 // defined in rust_task.cpp
-extern size_t g_min_stack_size;
+extern size_t g_custom_min_stack_size;
 extern "C" CDECL void
 set_min_stack(rust_task *task, uintptr_t stack_size) {
-    g_min_stack_size = stack_size;
+    g_custom_min_stack_size = stack_size;
 }
 
 //
diff --git a/src/rt/rust_env.cpp b/src/rt/rust_env.cpp
new file mode 100644
index 00000000000..26fc4dab180
--- /dev/null
+++ b/src/rt/rust_env.cpp
@@ -0,0 +1,119 @@
+// The runtime wants to pull a number of variables out of the
+// environment but calling getenv is not threadsafe, so every value
+// that might come from the environment is loaded here, once, during
+// init.
+
+#include "rust_internal.h"
+
+// The environment variables that the runtime knows about
+#define RUST_THREADS "RUST_THREADS"
+#define RUST_MIN_STACK "RUST_MIN_STACK"
+#define RUST_LOG "RUST_LOG"
+#define CHECK_CLAIMS "CHECK_CLAIMS"
+#define DETAILED_LEAKS "DETAILED_LEAKS"
+#define RUST_SEED "RUST_SEED"
+
+#if defined(__WIN32__)
+static int
+get_num_cpus() {
+    SYSTEM_INFO sysinfo;
+    GetSystemInfo(&sysinfo);
+
+    return (int) sysinfo.dwNumberOfProcessors;
+}
+#elif defined(__BSD__)
+static int
+get_num_cpus() {
+    /* swiped from http://stackoverflow.com/questions/150355/
+       programmatically-find-the-number-of-cores-on-a-machine */
+
+    unsigned int numCPU;
+    int mib[4];
+    size_t len = sizeof(numCPU);
+
+    /* set the mib for hw.ncpu */
+    mib[0] = CTL_HW;
+    mib[1] = HW_AVAILCPU;  // alternatively, try HW_NCPU;
+
+    /* get the number of CPUs from the system */
+    sysctl(mib, 2, &numCPU, &len, NULL, 0);
+
+    if( numCPU < 1 ) {
+        mib[1] = HW_NCPU;
+        sysctl( mib, 2, &numCPU, &len, NULL, 0 );
+
+        if( numCPU < 1 ) {
+            numCPU = 1;
+        }
+    }
+    return numCPU;
+}
+#elif defined(__GNUC__)
+static int
+get_num_cpus() {
+    return sysconf(_SC_NPROCESSORS_ONLN);
+}
+#endif
+
+static int
+get_num_threads()
+{
+    char *env = getenv(RUST_THREADS);
+    if(env) {
+        int num = atoi(env);
+        if(num > 0)
+            return num;
+    }
+    return get_num_cpus();
+}
+
+// FIXME (issue #151): This should be 0x300; the change here is for
+// practicality's sake until stack growth is working.
+
+static size_t
+get_min_stk_size() {
+    char *stack_size = getenv(RUST_MIN_STACK);
+    if(stack_size) {
+        return strtol(stack_size, NULL, 0);
+    }
+    else {
+        return 0x300000;
+    }
+}
+
+static char*
+copyenv(const char* name) {
+    char *envvar = getenv(name);
+    if (!envvar) {
+        return NULL;
+    } else {
+        const size_t maxlen = 4096;
+        size_t strlen = strnlen(envvar, maxlen);
+        size_t buflen = strlen + 1;
+        char *var = (char*)malloc(buflen);
+        memset(var, 0, buflen);
+        strncpy(var, envvar, strlen);
+        return var;
+    }
+}
+
+rust_env*
+load_env() {
+    rust_env *env = (rust_env*)malloc(sizeof(rust_env));
+
+    env->num_sched_threads = (size_t)get_num_threads();
+    env->min_stack_size = get_min_stk_size();
+    env->logspec = copyenv(RUST_LOG);
+    env->check_claims = getenv(CHECK_CLAIMS) != NULL;
+    env->detailed_leaks = getenv(DETAILED_LEAKS) != NULL;
+    env->rust_seed = copyenv(RUST_SEED);
+
+    return env;
+}
+
+void
+free_env(rust_env *env) {
+    free(env->logspec);
+    free(env->rust_seed);
+    free(env);
+}
diff --git a/src/rt/rust_env.h b/src/rt/rust_env.h
new file mode 100644
index 00000000000..6dc9cc120cd
--- /dev/null
+++ b/src/rt/rust_env.h
@@ -0,0 +1,11 @@
+struct rust_env {
+    size_t num_sched_threads;
+    size_t min_stack_size;
+    char* logspec;
+    bool check_claims;
+    bool detailed_leaks;
+    char* rust_seed;
+};
+
+rust_env* load_env();
+void free_env(rust_env *rust_env);
diff --git a/src/rt/rust_internal.h b/src/rt/rust_internal.h
index 6fe3e170b79..10822f02395 100644
--- a/src/rt/rust_internal.h
+++ b/src/rt/rust_internal.h
@@ -24,6 +24,7 @@
 #include "rust.h"
 #include "rand.h"
 #include "uthash.h"
+#include "rust_env.h"
 
 #if defined(__WIN32__)
 extern "C" {
diff --git a/src/rt/rust_kernel.cpp b/src/rt/rust_kernel.cpp
index 8839f7fe6af..a4f56c10be2 100644
--- a/src/rt/rust_kernel.cpp
+++ b/src/rt/rust_kernel.cpp
@@ -12,7 +12,8 @@ rust_kernel::rust_kernel(rust_srv *srv, size_t num_threads) :
     _interrupt_kernel_loop(FALSE),
     num_threads(num_threads),
     rval(0),
-    live_tasks(0)
+    live_tasks(0),
+    env(srv->env)
 {
     isaac_init(this, &rctx);
     create_schedulers();
@@ -51,6 +52,8 @@ rust_kernel::destroy_scheduler(rust_scheduler *sched) {
 }
 
 void rust_kernel::create_schedulers() {
+    KLOG_("Using %d scheduler threads.", num_threads);
+
     for(size_t i = 0; i < num_threads; ++i) {
         threads.push(create_scheduler(i));
     }
diff --git a/src/rt/rust_kernel.h b/src/rt/rust_kernel.h
index cf9d88e0016..d54c6a65430 100644
--- a/src/rt/rust_kernel.h
+++ b/src/rt/rust_kernel.h
@@ -98,6 +98,8 @@ public:
      */
     indexed_list<rust_message_queue> message_queues;
 
+    struct rust_env *env;
+
     rust_handle<rust_task> *get_task_handle(rust_task *task);
     rust_handle<rust_port> *get_port_handle(rust_port *port);
 
diff --git a/src/rt/rust_scheduler.cpp b/src/rt/rust_scheduler.cpp
index 245ee3d5fce..c4987bbd3f1 100644
--- a/src/rt/rust_scheduler.cpp
+++ b/src/rt/rust_scheduler.cpp
@@ -20,7 +20,9 @@ rust_scheduler::rust_scheduler(rust_kernel *kernel,
     cache(this),
     kernel(kernel),
     message_queue(message_queue),
-    id(id)
+    id(id),
+    min_stack_size(kernel->env->min_stack_size),
+    env(kernel->env)
 {
     LOGPTR(this, "new dom", (uintptr_t)this);
     isaac_init(this, &rctx);
diff --git a/src/rt/rust_scheduler.h b/src/rt/rust_scheduler.h
index 9289883ab1e..561807d44e0 100644
--- a/src/rt/rust_scheduler.h
+++ b/src/rt/rust_scheduler.h
@@ -60,11 +60,14 @@ struct rust_scheduler : public kernel_owned<rust_scheduler>,
     const int id;
 
     lock_and_signal lock;
+    size_t min_stack_size;
 
 #ifndef __WIN32__
     pthread_attr_t attr;
 #endif
 
+    rust_env *env;
+
     // Only a pointer to 'name' is kept, so it must live as long as this
     // domain.
     rust_scheduler(rust_kernel *kernel,
diff --git a/src/rt/rust_srv.cpp b/src/rt/rust_srv.cpp
index 05c9d9d564c..835b283a73f 100644
--- a/src/rt/rust_srv.cpp
+++ b/src/rt/rust_srv.cpp
@@ -1,7 +1,8 @@
 #include "rust_internal.h"
 #include "rust_srv.h"
 
-rust_srv::rust_srv() :
+rust_srv::rust_srv(rust_env *env) :
+    env(env),
     local_region(this, false) {
 }
 
@@ -72,7 +73,7 @@ rust_srv::warning(char const *expression,
 
 rust_srv *
 rust_srv::clone() {
-    return new rust_srv();
+    return new rust_srv(env);
 }
 
 //
diff --git a/src/rt/rust_srv.h b/src/rt/rust_srv.h
index beec5d70345..7037007e78c 100644
--- a/src/rt/rust_srv.h
+++ b/src/rt/rust_srv.h
@@ -6,6 +6,7 @@
 
 class rust_srv {
 public:
+    rust_env *env;
     memory_region local_region;
     virtual void log(char const *msg);
     virtual void fatal(char const *expression,
@@ -21,7 +22,7 @@ public:
     virtual void free(void *);
     virtual void *malloc(size_t);
     virtual void *realloc(void *, size_t);
-    rust_srv();
+    rust_srv(rust_env *);
     virtual ~rust_srv();
     virtual rust_srv *clone();
 };
diff --git a/src/rt/rust_task.cpp b/src/rt/rust_task.cpp
index a144879cc04..6f3e0202472 100644
--- a/src/rt/rust_task.cpp
+++ b/src/rt/rust_task.cpp
@@ -10,28 +10,25 @@
 
 #include "globals.h"
 
-// Stacks
+// Stack size
+size_t g_custom_min_stack_size = 0;
 
-// FIXME (issue #151): This should be 0x300; the change here is for
-// practicality's sake until stack growth is working.
-size_t g_min_stack_size = 0x300000;
-
-static size_t get_min_stk_size() {
-    char *stack_size = getenv("RUST_MIN_STACK");
-    if(stack_size) {
-        return strtol(stack_size, NULL, 0);
-    }
-    else {
-        return g_min_stack_size;
+static size_t
+get_min_stk_size(size_t default_size) {
+    if (g_custom_min_stack_size != 0) {
+        return g_custom_min_stack_size;
+    } else {
+        return default_size;
     }
 }
 
+
 // Task stack segments. Heap allocated and chained together.
 
 static stk_seg*
-new_stk(rust_task *task, size_t minsz)
+new_stk(rust_scheduler *sched, rust_task *task, size_t minsz)
 {
-    size_t min_stk_bytes = get_min_stk_size();
+    size_t min_stk_bytes = get_min_stk_size(sched->min_stack_size);
     if (minsz < min_stk_bytes)
         minsz = min_stk_bytes;
     size_t sz = sizeof(stk_seg) + minsz;
@@ -90,7 +87,7 @@ rust_task::rust_task(rust_scheduler *sched, rust_task_list *state,
     LOGPTR(sched, "new task", (uintptr_t)this);
     DLOG(sched, task, "sizeof(task) = %d (0x%x)", sizeof *this, sizeof *this);
 
-    stk = new_stk(this, 0);
+    stk = new_stk(sched, this, 0);
     rust_sp = stk->limit;
 }
 
diff --git a/src/rt/rust_util.h b/src/rt/rust_util.h
index c46f1916573..938b4c96cb5 100644
--- a/src/rt/rust_util.h
+++ b/src/rt/rust_util.h
@@ -148,7 +148,7 @@ isaac_init(sched_or_kernel *sched, randctx *rctx)
                  CryptReleaseContext(hProv, 0));
         }
 #else
-        char *rust_seed = getenv("RUST_SEED");
+        char *rust_seed = sched->env->rust_seed;
         if (rust_seed != NULL) {
             ub4 seed = (ub4) atoi(rust_seed);
             for (size_t i = 0; i < RANDSIZ; i ++) {
diff --git a/src/rt/test/rust_test_runtime.cpp b/src/rt/test/rust_test_runtime.cpp
index 1e7c10944a7..ad5a018eec8 100644
--- a/src/rt/test/rust_test_runtime.cpp
+++ b/src/rt/test/rust_test_runtime.cpp
@@ -19,7 +19,8 @@ rust_domain_test::worker::run() {
 
 bool
 rust_domain_test::run() {
-    rust_srv srv;
+    rust_env env;
+    rust_srv srv(&env);
     rust_kernel kernel(&srv, 1);
 
     array_list<worker *> workers;
@@ -51,7 +52,8 @@ rust_task_test::worker::run() {
 
 bool
 rust_task_test::run() {
-    rust_srv srv;
+    rust_env env;
+    rust_srv srv(&env);
     rust_kernel kernel(&srv, 1);
 
     array_list<worker *> workers;
diff --git a/src/rt/test/rust_test_util.h b/src/rt/test/rust_test_util.h
index 9ee3ee8bd36..59eff049270 100644
--- a/src/rt/test/rust_test_util.h
+++ b/src/rt/test/rust_test_util.h
@@ -17,10 +17,13 @@ public:
 
 class rust_synchronized_indexed_list_test : public rust_test {
 public:
+    rust_env env;
     rust_srv srv;
     synchronized_indexed_list<indexed_list_element<int> > list;
 
-    rust_synchronized_indexed_list_test() {
+    rust_synchronized_indexed_list_test() :
+        srv(&env)
+    {
     }
 
     class worker : public rust_thread {